Transsplenic portal catheterization combined with a jugular double-lumen catheter for pharmacokinetic and presystemic metabolization studies in pigs

The reliability of a silicone double-lumen catheter implanted into the external jugular vein and tunnelled towards the neck region was investigated in eight pigs. Surgery was uneventful without interference with the normal homoeostasis during 8 days. After injection of amoxicillin/clavulanic acid through the distal port of the catheter, analysis of drug components in the simultaneous blood samples obtained by the proximal port and a Venoject^® system were comparable in one pig. Histological control of the catheterized jugular veins pointed to an acceptable tissue reaction while bacteriological examination of the tip of the catheters was negative in only three animals. A moulding of the intestinal veins was made in a pig cadaver to determine the optimal length of insertion of a silicone portal catheter from the splenic vein towards the portal vein. Surgery was straightforward in four pigs whereby the catheter was exteriorized towards the back region. No complications were encountered during and after surgery for 9 days. The technique of a double-lumen catheter placed into the jugular vein and a transsplenic portal catheter is a useful tool for the study of the pharmacokinetics and also the first-pass effect of drugs in experimental pigs.     

Long-term cannulation of the ovarian vein in mares.

A cannulation technique was developed to collect blood samples from the ovarian vein of mares over an extended period. Ovarian venous cannulae placed in 4 mares remained patent for a mean (+/- SEM) duration of 36.8 (+/- 6.2) days. During mid-diestrus, concentrations of progesterone in the ovarian vein ipsilateral to the corpus luteum (1,663.8 +/- 238.8 ng/ml) were significantly (P less than 0.001) higher than concentrations measured in paired samples from the jugular vein (6.1 +/- 0.3 ng/ml). Concentration of estradiol in the ovarian vein ranged from a mean of 1,053.2 +/- 303.1 pg/ml during diestrus to 3,353.8 +/- 1,052.8 pg/ml during estrus, whereas values for 74% of samples collected concurrently from the jugular vein were near or below the sensitivity of the assay (10 pg/ml). Results of the study indicate that patent long-term ovarian vein cannulation can be achieved in mares. The cannulation technique provides access to important fundamental information on equine reproductive endocrinology, which to our knowledge, has not been available.     

A method for chronically quantifying net absorption of nutrients and gut metabolites into hepatic portal vein in conscious swine

Surgical procedures are described for chronic cannulation of portal vein, ileal vein, abdominal aorta, and carotid artery in pigs. Silastic or Micro-Renathane tubing was used for cannulating portal vein and ileal vein, while carotid artery was cannulated with Micro-Renathane tubing. The lumen of Micro-Renathane tubing was coated with tri-dodecylmethyl ammonium chloride (TDMAC)-heparin complex. The abdominal aorta was cannulated via saphenous artery with vinyl tubing. This allows simultaneous collection of blood samples from hepatic portal vein and systemic artery (carotid or abdominal aorta) and continuous infusion of p-aminohippuric acid (PAH) into ileal vein. The constant PAH infusion provided an indicator-dilution method for estimating the blood flow rate in portal vein. In 13 pigs weighing 54 +/- 2.8 kg, the mean portal vein blood flow rate during the 8-h postprandial period was estimated to be 1,979 ml X min-1 X pig-1 or 37.8 ml X min-1 X kg-1 body weight. By simultaneously measuring the concentration of nutrients and metabolites in the portal and systemic arterial blood and multiplying porto-arterial differences by the estimated portal vein blood flow rate, the net absorption of nutrients (except long-chain fatty acids) and metabolites into hepatic portal system in conscious swine can be quantified.     

Difference in rates of net portal absorption between crystalline and protein-bound lysine and threonine in growing pigs fed once daily

Net portal absorption of AA during the 6-h postprandial period was measured in eight gilts (48.5 +/- 1.6 kg BW) in a crossover design. The pigs had chronic catheters placed in the portal vein, carotid artery, and ileal vein, and were trained to consume 1.2 kg of a standard grower diet once daily. Blood samples were taken every 30 min for 4 h and then hourly until 6 h after feeding. The first set of blood samples was taken after pigs were fed a meal of the test 16% CP corn-soybean meal diet (16% CP) or the test 12% CP corn-soybean meal diet supplemented with crystalline lysine, threonine, and tryptophan (12% CP + AA) to equal the three AA levels in the 16% CP diet. Pigs were then fed the standard diet for 2 d. Following that, blood samples were again taken after the pigs were fed a meal of the test diet that was not given to them at the first sampling period. Net portal AA absorption was calculated by multiplying porto-arterial plasma AA concentration difference by portal vein plasma flow rate (PVPF), estimated by an indicator-dilution technique employing p-aminohippuric acid as the indicator infused into the ileal vein. Plasma concentrations of lysine and threonine of pigs were affected by the diet x time interaction (P < 0.01). Portal and arterial plasma lysine and threonine concentrations in pigs attained the maximal level by 1 h postprandial when the 12% CP + AA diet was fed, but reached the peak level at 2.5 h postprandial when the 16% CP diet was given. The PVPF of pigs over the 6 h postprandial was less (P < 0.01) when the 12% CP + AA diet was given than when the 16% CP diet was fed. Net portal absorptions of lysine and threonine also were affected (P < 0.05) by time x diet interaction. The peak portal absorption of both lysine and threonine in pigs appeared at 0.5 h postprandial when the 12% CP + AA diet was given, but at 2.5 h postprandial with the feeding of the 16% CP diet. The early appearance of peak portal absorption of lysine and threonine from feeding the 12% CP + AA compared with the 16% CP diet indicates that crystalline lysine and threonine are absorbed more rapidly than protein-bound lysine and threonine in pigs fed once daily.     

Effects of sodium dichloroacetate in awake, healthy, Yucatan miniature swine

Four healthy, fully conscious, 50- to 80-kg Yucatan miniature swine were fitted with carotid artery and jugular, portal, and hepatic vein catheters and hepatic artery and portal vein flow cuffs to determine transhepatic kinetics and insulin secretion. Three days later, after a 3-hour control period, the pigs were given IV sodium dichloroacetate (30 mg/kg of body weight as a bolus and 30 mg/kg/hr, as an infusion) for 6 hours. Arterial lactate concentrations decreased during the dichloroacetate infusion, but pyruvate concentrations were unaltered. The whole body rate of appearance and disappearance of glucose decreased, but plasma glucose concentrations did not change markedly. Limb skin surface temperatures increased, indicating a peripheral vasodilatory effect. Dichloroacetate had little effect on mean arterial pressure and hepatosplanchnic blood flow. Dichloroacetate may be effective as a hypolactatemic agent for lactic acidosis in pigs.     

半乳甘露寡糖对猪门静脉血流速率、氨基酸和葡萄糖的净吸收量及耗氧量的影响

通过对10头15kg体重试验猪实施门静脉血管插管等外科手术,并结合回肠肠系膜静脉灌注对氨基马尿酸(PAH)技术,探讨半乳甘露寡糖对生长猪门静脉血浆流率(PVPF)和血液流率(PVBF)、氨基酸和葡萄糖的净吸收量及耗氧量的影响。10头杜长大阉公猪随机分为2个处理,每个处理5头,单笼饲养于可调节不锈钢代谢笼内,经过14d适应期后,在门静脉、肠系膜静脉、颈动脉安装插管,开始15d正式试验。对照组饲喂玉米-豆粕型基础饲粮,试验组饲喂基础饲粮 0.20%半乳甘露寡糖。结果表明,经过15d饲喂期后,与对照组相比,饲粮添加半乳甘露寡糖可显著降低试猪食后8h内门静脉的平均血浆流率和血液流率,显著提高食后8h内门静脉对氨基酸和葡萄糖的净吸收量,显著降低食后8h内门静脉的耗氧量,也就是说半乳甘露寡糖可通过减少生长猪小肠黏膜对氨基酸和葡萄糖的氧化而增加肠外组织对其吸收。     

The effect of birth weight and feeding of supplemental milk replacer to piglets during lactation on preweaning and postweaning growth performance and carcass characteristics

The effects of piglet birth weight and liquid milk replacer supplementation of piglets during lactation on growth performance to slaughter weight was evaluated in a study carried out with 32 sows (PIC C-22) and their piglets (n = 384; progeny of PIC Line 337 sires). A randomized block design with a 2 x 2 factorial arrangement of treatments was used. Treatments were birth weight (Heavy vs Light) and liquid milk replacer (Supplemented vs Unsupplemented). The study was divided into two periods. At the start of period 1 (birth to weaning), pigs were assigned to either Heavy or Light (1.8 [SD = 0.09] vs 1.3 kg [SD = 0.07] BW, respectively, P < 0.001) litters of 12 pigs and half of the litters were given ad libitum access to supplemental milk replacer from d 3 of lactation to weaning (21 +/- 0.2 d). In period 2 (weaning to 110 kg BW), a total of 308 pigs were randomly selected from within previous treatment and sex subclasses and placed in pens of four pigs. Pigs were given ad libitum access to diets that met or exceeded nutrient requirements. Pigs in heavy litters were heavier at weaning (6.6 vs 5.7 kg BW; SE = 0.14; P < 0.001) and tended to have more pigs weaned (11.4 vs 10.9 pigs/litter; SE = 0.21; P = 0.10). After weaning, pigs in the Heavy litter had greater ADG (851 vs 796 g; SE = 6.7; P < 0.001) and ADFI (1,866 vs 1,783 g; SE = 17.6; P < 0.001), similar gain:feed (0.46 vs 0.45; SE = 0.003; P > 0.05), and required seven fewer days (P < 0.001) to reach slaughter weight compared to pigs in the Light treatment. Feeding supplemental milk replacer during lactation produced heavier pigs at weaning (6.6 vs 5.7 kg BW; SE = 0.14; P < 0.001) and tended to increase the number of pigs weaned (11.4 vs 10.9 pigs/litter; SE = 0.21; P = 0.10) but had no effect (P > 0.05) on growth performance from weaning to slaughter. However, pigs fed milk replacer required three fewer days (P < 0.01) to reach 110 kg BW. Sow feed intake and BW loss during lactation were not affected (P > 0.05) by either birth weight or milk replacer treatment. In conclusion, birth weight has a substantially greater impact on pig growth performance after weaning than increasing nutrient intake during lactation.     

Immunological parameters in the intestinal lymph of pigs including changes during experimentally induced diarrhoea

Experiments were undertaken to provide basic immunological data on the intestinal lymph of young pigs. For this purpose indwelling cannulae were established in the main efferent intestinal lymphatic ducts of 12 animals and measurements were made of lymph flow rate, and concentrations of IgG, IgA and IgM. Measurements were also made of cell numbers, differential counts and immunoglobulin specificity of lymphoid cells in lymph. Similar measurements were also made on six pigs in which experimental diarrhoea was induced. The mean number of leucocytes in intestinal lymph was extremely low (0.66 X 10(5)/ml). However a high proportion of lymphocytes contained cytoplasmic IgA (19.65 per cent) and IgM (12.53 per cent), with few containing IgG (1.35 per cent). The concentrations of IgM and IgA in intestinal lymph were 0.51 mg/ml and 1.64 mg/ml respectively, values which suggest that the intestine is an important organ for synthesis of these two classes of immunoglobulin in young pigs. Following induction of diarrhoea and consequent dehydration of the intestine, the lymph: serum concentration ratios for immunoglobulins increased but subsequently declined when the water balance in the intestine returned to normal.     

Concentrations of free steroids in the jugular and hepatic portal veins of pigs after ingestion of testosterone, estrogen, or progesterone or transplantation of ovaries to the intestine.

Estrogen, progesterone or testosterone were administered orally to ovariectomized gilts fitted with indwelling catheters. Blood samples were taken from the jugular and hepatic portal veins at intervals varying from a few minutes to daily over periods that varied from 1 d to several months. Concentrations of free steroids rose dramatically in the hepatic portal vein within a few min of feeding steroids and remained high for 3-8 hr before declining to base levels. Concentrations in the jugular vein sometimes rose very slightly for the same period. At 48 hr after administration the concentrations remained at baseline in the hepatic portal vein, but rose several-fold in the jugular and remained elevated for several days. Autotransplantation of the ovaries to the intestine resulted in very large ovaries consisting of many large, heavily luteinized cystic follicles. Concentrations of progesterone and estrogen in the hepatic portal vein were very high, but were low in the jugular vein. The gut wall allows for passage of some orally administered free steroids to the liver via the hepatic portal vein. The free steroids are essentially metabolized before they reach the jugular vein, but can be recirculated via the enterohepatic route.     

Effect of carbadox on net absorption of ammonia and glucose into hepatic portal vein of growing pigs

Chronic cannulas were placed into the hepatic portal vein, ileal vein and carotid artery of growing pigs trained to consume their daily allowance of 1.2 kg of feed (16% protein corn-soybean meal basal diet) in a single meal. The average preoperative BW of pigs was 44.7 kg for Trial 1 (three pigs) and 35.3 kg for Trial 2 (seven pigs). In Trial 1, net absorption of ammonia (NH3) and glucose into the portal vein was determined three times at weekly intervals. The net portal absorptions were derived by multiplying the porto-arterial plasma concentration difference of NH3 and glucose by portal vein plasma flow rate estimated with the p-aminohippuric acid indicator-dilution technique. Differences in the net portal absorptions of NH3 and glucose among the three weekly measurements were small (P greater than .05). In Trial 2, the first sequence of net portal absorption measurements was conducted when pigs were fed the basal diet, and the second sequence of measurements was conducted after the pigs had been fed the diet supplemented with 55 ppm of carbadox for 7 d. Carbadox supplementation reduced (P less than .05) plasma NH3 concentration in portal plasma during the 2.5-h to 5-h postprandial period and decreased (P less than .05) net portal absorption of NH3 during the 2.5-h to 4-h postprandial period. Carbadox, however, did not affect (P greater than .05) net portal absorption of glucose. We suggest that carbadox suppresses the production of cell-toxic NH3 by intestinal microorganisms and, thus, reduces the injury and turnover of intestinal cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Potential contribution of absorbed volatile fatty acids to whole-animal energy requirement in conscious swine

Chronic cannulas were placed in the hepatic portal vein, ileal vein, and carotid artery in seven crossbred growing gilts trained to consume once daily 1.2 kg of a 16% CP corn-soybean meal diet. Eleven days after surgery, each pig (37.4 kg BW) was placed in an open-circuit calorimeter and its cannulas were connected to a system for determining portal absorption of nutrients. The whole-animal heat production and net portal absorption of gut VFA were measured simultaneously for 12 h after the pig was fed 1.2 kg of feed. Plasma concentrations of VFA, including acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids, in portal and arterial samples were determined by gas chromatography after a cleanup by ion-exchange chromatography. The net portal absorption of VFA was calculated by multiplying the porto-arterial plasma concentration difference of the VFA by portal vein plasma flow. Plasma flow was estimated by the indicator-dilution technique using p-aminohippuric acid as the indicator. The energy value of absorbed VFA was the sum of products of each individual VFA multiplied by its corresponding value of the heat of combustion. The mean hourly energy value of absorbed VFA during the 12-h postprandial period was .65 +/- .03 kcal.h-1.kg BW-1. The mean hourly whole-animal heat production was 2.70 +/- .04 kcal.h-1.kg BW-1. Thus, in our 37.4-kg pigs, which were trained to consume 1.2 kg of a 16% CP corn-soybean meal diet once daily, the gut VFA absorbed into the portal vein could contribute 23.8 +/- 1.1% to whole-animal heat production if all of the absorbed VFA were combusted to CO2.     

Intestinal absorption of end products from digestion of carbohydrates and proteins in the pig

The kinetics of appearance of various nutrients in the portal vein during the postprandial period was studied in conscious pigs by means of a technique based on measurement of the porto-arterial differences in nutrient concentrations simultaneously with that of the portal blood flow rate. The rate and level of appearance of sugars in the portal vein varied with the carbohydrate ingested. It was very rapid after intake of glucose and sucrose, slower after that of maize starch and very slow after that of lactose. The absorption of the latter became very rapid again if it was hydrolysed prior to its ingestion. During absorption, some sugars (fructose or galactose) released from the corresponding sucrose and lactose, respectively during digestion, were partly metabolized into glucose by the enterocyte. The rate of absorption of amino acids released in the digestive tract varied according to the origin of the food ingested, i.e. it was more rapid after intake of wheat or fish proteins than after that of barley. In the case of barley the absorption rate of amino acids differed from that of glucose of the starch. The profile of the amino acid mixtures appearing in the portal vein during absorption differed a little from the profiles of those present in the ingested proteins in the case of essential amino acids and differed much in the case of non essential amino acids. Some essential amino acids (histidine, aromatic amino acids) appeared more rapidly and others more slowly, (lysine, sulphur amino acids, arginine). Because of transaminations, only small amounts of glutamic acid occurred in the portal vein whereas the amounts of alanine as compared to those ingested, were very large. The hierarchy of amino acid absorption was the same whatever the protein studied (fish, wheat, barley). The appearance in the portal vein of alpha-amino nitrogen from enzyme hydrolysates perfused through the duodenum was more rapid than after perfusion of a mixture of free amino acids. During digestion of diets containing 6% cellulose, large amounts of volatile fatty acids (about 2200 mmol/24 h, i.e. 2500 kJ/24h) and lactic acid (60-85 g/24 h) appeared in the portal vein.     

Blood pressure, heart rate, hormonal and other acute responses to rubber-ring castration and tail docking of lambs

AIM: To examine cardiovascular, hormonal and other physiological responses of 2-month-old lambs to rubber-ring castration and tail docking. METHODS: Twenty-two male lambs, well accustomed to handling and prepared with femoral artery and jugular vein cannulae, were studied during a 5 h control period and, at least 2 days later, for 1 h before and 4 h after castration and tail docking using rubber rings. Pressure recordings were made via femoral cannulae and blood samples for analysis of plasma constituents were taken from jugular cannulae. RESULTS: Mean systolic, diastolic and mean arterial blood pressure, heart rate and the plasma concentrations of adrenocorticotropic hormone (ACTH) and cortisol all increased markedly during the first 1 h after ring castration and tail docking. Although plasma ACTH and cortisol concentrations had returned to control levels by 2.5-3 h, blood pressures and heart rate were still elevated 4 h after ring application. In contrast, there were no significant changes in mean plasma concentrations of renin, electrolytes, minerals, glucose, lactate, urea, creatinine, total carbon dioxide and total proteins, plasma osmolality or the haematocrit after ring application. There were no significant changes in the mean values for any parameter during the 5 h control period or the 1 h period before ring application. CONCLUSION: Systolic, diastolic and mean arterial blood pressure and heart rate may be more sensitive than plasma ACTH or cortisol concentrations as indices of low-grade pain induced by ring castration and tail docking. Alternatively, it is possible that by 4 h after ring placement a small shift in sympathetic tone still persists in the absence of low-grade pain.     

Absorption and metabolism of alpha-ketoglutarate in growing pigs

The portal appearance of enteral alpha-ketoglutarate (AKG) and the effect of enteral or parenteral AKG on portal net appearance of glucose, short-chain fatty acids, alanine, aspartate, glutamate, glutamine, proline and insulin were investigated in three growing pigs. During the experimental samplings the pigs were fed hourly with a standard feed mix with 5% glucose (control), 5% AKG (enteral) or no feed additive but continuously infused with AKG into the mesenteric vein in an amount equivalent to 5% of feed intake (parenteral). The arterial plasma concentration of AKG increased (p < 0.05) following both enteral (from 16+/-2 to 22+/-3 micromol/l) and parenteral (from 16+/-2 to 425+/-27 micromol/l) administration of AKG. With the enteral treatment 4+/-1% of the AKG could be accounted for in the portal vein, however, with the parenteral treatment 86+/-5% could be accounted for in the portal vein. The arterial plasma concentration of proline increased (p < 0.05) with the enteral treatment (365 +/- 3 to 443 +/- 39 micromol/l), but was not affected by the parenteral treatment (p > 0.10). The plasma concentration glutamine decreased (p < 0.05) with the parenteral treatment only. The portal net appearance of proline showed a numerical increase with the enteral treatment but no other affects on arterial concentrations or portal net appearance were found. A small accompanying study showed that only small amounts of enteral AKG was present in the small intestine. It was therefore concluded that enteral AKG has a low availability to peripheral tissues either because it is absorbed and metabolized in the stomach and duodenum or because it is metabolized by microbes in the stomach. The study showed that AKG is metabolized differently following enteral and parenteral application in growing pigs.     

Distribution of persistent Salmonella typhimurium infection in internal organs of swine

Experiments were conducted to establish a persistent Salmonella typhimurium infection in convalescent swine, and to determine rate of shedding and distribution of the organism in internal organs. Naturally farrowed Salmonella-free pigs (n = 37) were orally exposed to S typhimurium when 7 to 8 weeks old. Fecal samples, tonsillar scrapings, and rectal swab specimens were examined bacteriologically for S typhimurium at weekly intervals after exposure until necropsy (maximum of 28 weeks after exposure). Necropsies of 1 to 4 randomly selected pigs were conducted at 2, 4, and 7 days and at 2, 4, 6, 8, 12, 16, 20, 24, and 28 weeks after exposure. The following internal organs were examined bacteriologically for S typhimurium: liver, spleen, kidney, gallbladder, heart, lung, and stomach; segments of the intestinal tract with corresponding lymph nodes; lymph nodes from lymphocenters of the head and neck, thoracic and abdominal cavities, pelvic wall, and thoracic and pelvic limbs. Fecal samples were 83 to 100% culture-positive up to postexposure (PE) week 22, then varied from 14 to 67% positive until PE week 28. At least 60% of tonsillar swab specimens and 50% of rectal swab specimens were culture-positive up to PE week 20, after which they varied from 0 to 70% positive until PE week 28. At necropsy, S typhimurium was recovered most frequently from tonsils (93.5% positive), followed by segments of the intestinal tract from caudal portion of jejunum to rectum (71% recovery from cecum), and mandibular (54.8%) and ileocolic (45.2%) lymph nodes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of carbadox on fasting oxygen consumption by portal vein-drained organs and by the whole animal in growing pigs.

Fasting O2 consumption by the whole animal (W) and by portal vein-drained organs (PVDO) during the 24- to 30-h postprandial period were measured in seven growing pigs (36.1 +/- 2.3 kg) with catheters chronically placed in the hepatic portal vein, ileal vein, and carotid artery trained to consume 1.2 kg of a 16% CP corn soybean meal basal diet (B) once daily. The pigs were placed individually into an open-circuit, indirect calorimeter and connected to an arteriovenous (A-V) O2 difference analyzer for hourly simultaneous measurements of O2 consumption by W and PVDO. The PVDO O2 consumption was calculated by multiplying the A-V O2 difference by the portal vein blood flow rate derived from constant infusion of a p-aminohippuric acid solution into the ileal vein. After the initial series of hourly measurements, four pigs remained on the B diet and three pigs were fed a B + 55 ppm carbadox diet. Seven days later, the second series of measurements was made. In pigs fed the diet with carbadox added, the hourly W O2 consumptions were not different (P greater than .05) between the initial and second series and averaged 7.5 mL.min-1.kg of BW-1. However, the A-V O2 differences (mL/dL) were reduced (P less than .05) from 4.6 to 4.0 at 24 h, 4.8 to 4.0 at 25 h, and 4.6 to 4.0 at 29 h postprandial and the fractions of W O2 consumption used by PVDO (percentage) were reduced (P less than .05) from 28.6 to 21.6 at 26 h and 25.2 to 18.2 at 27 h postprandial.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrasound-guided percutaneous portocentesis in 21 cows

An ultrasound-guided portocentesis was performed in 21 clinically healthy cows, and blood was collected for haematological, biochemical and blood-gas analyses. At the same time blood samples were collected from the left jugular vein of each cow for the same analyses. Immediately after the centesis, portal blood pressure was measured. The cows were examined daily thereafter for eight days and then slaughtered for postmortem examination of the internal organs. The mean (sd) portal blood pressure was 37.1 (5.47) mmHg, and ranged from 24 to 49 mmHg. There were small but significant differences between many of the haematological and biochemical parameters in jugular and portal blood, and the concentration of bile acids was on average 2.7 times higher, and the concentration of ammonia was 19.3 times higher in portal blood. The demeanour and behaviour of the cows, and their appetite and rectal temperature remained normal during the eight-day observation period. The haematocrit, total and differential leucocyte counts, and the concentrations of total solids and fibrinogen were not affected by portocentesis. On postmortem examination, no lesions were apparent in the peritoneum, liver and portal vein.     

Examination of metabolism of viscera drained by the portal vein in neonatal calves, using short-term intravenous infusions of glutamine and other nutrients

OBJECTIVE: To quantify glutamine use in viscera drained by the portal vein in neonatal calves and to assess the relative nutritional importance of glutamine, glucose, and acetate for enterocytes. ANIMALS: 5 healthy neonatal calves. PROCEDURE: A femoral artery, jugular vein, and the portal vein were surgically cannulated in each calf. Blood flow in the portal vein was measured by use of an ultrasonographic transit-time flow probe. A series of solutions was infused on 4 days for each calf. On the infusion days, acetate, glucose, glutamine, and saline (0.9% NaCl; control) solutions were administered IV during 1-hour periods via the jugular vein. Venous and arterial blood samples were collected during the last 15 minutes of each 1-hour infusion. RESULTS: Uptake of glutamine and glucose by viscera drained by the portal vein was 0.3+/-1.1 and 1.9+/-3.1 micromol/kg0.75/min, respectively, during saline infusion. During acetate, glucose, and saline infusions, glucose was a greater source of energy for the intestines than was glutamine. However, during glutamine infusion, uptake of glutamine by viscera drained by the portal vein increased significantly (29.9+/-11.2 micromol/kg0.75/min), which was associated with an increase in ammonia production (7.0+/-0.5 micromol/kg0.75/min). Toxicosis was not associated with IV administration of glutamine. CONCLUSION: Glutamine infusion resulted in an increase in glutamine uptake by viscera drained by the portal vein, which was associated with an increase in ammonia production and a slight increase in oxygen consumption. CLINICAL RELEVANCE: These solutions may be used to develop treatments that enhance healing of intestines of diarrheic calves.     

Evaluation of splanchnic oxygen extraction ratio as an index of portal vein pressure in dogs

OBJECTIVE: To determine changes in splanchnic oxygen extraction ratio during experimentally induced portal hypertension in dogs. ANIMALS: 6 clinically normal dogs. PROCEDURE: Standard midline laparotomy and median sternotomy were performed in anesthetized dogs. Baseline measurements of arterial blood pressure, aortic blood flow, portal vein blood flow, and portal vein pressure were acquired, and arterial, venous, and portal vein blood samples were obtained to determine systemic and splanchnic oxygen extraction ratios. The portal vein was gradually occluded until a pressure of 18 cm of H2O was reached; this pressure was maintained for 30 minutes, and measurements and collection of blood samples were repeated. RESULTS: Portal vein blood flow decreased significantly from 457 +/- 136 ml/min before to 266 +/- 83 ml/min after induction of portal hypertension. Oxygen content in the portal vein significantly decreased from 12.3 +/- 1.85 to 8.2 +/- 2.31%, and splanchnic oxygen extraction ratio significantly increased from 15.8 +/- 6.2 to 37.4 +/- 10.9% during portal hypertension. There was a significant inverse correlation between portal vein blood flow and splanchnic oxygen extraction ratio at baseline and during portal hypertension. CONCLUSIONS AND CLINICAL RELEVANCE: An increase in splanchnic oxygen extraction ratio is evident with partial attenuation of the portal vein and the concurrent decrease in portal vein blood flow. Correlation of oxygen extraction ratio with portal vein blood flow may be a more important indicator for determination of an endpoint to prevent congestion and ischemia of the gastrointestinal tract and pancreas during ligation of portosystemic shunts.     

Quantitative measurement of endogenous amino acid absorption in unanaesthetized pigs

The present experiment was carried out with 11 pigs (mean body weight: 53.9 +/- 1.3 kg) fitted with permanent catheters in the portal vein and carotid artery and with an electromagnetic flow probe around the portal vein. They were each subjected to 2 or 3 trials at 3 to 4-day intervals. During each trial the animals received after a previous fasting of 20 h a given amount of a protein-free diet (200 to 1200 g). The blood was collected either continuously for a quantitative determination of amino nitrogen, reducing sugars, urea and ammonia (number of meals 12, mean intake: 727 +/- 60 g) or discontinuously every 30 min between 0 and 8 h after the meal for amino acid analysis (number of meals 8; mean intake 709 +/- 105 g). A rather constant appearance (2 g/h) of amino acids in the portal blood was observed throughout the postprandial period. The intestinal absorption of each amino acid was however variable and represented between 10 and 50% of the daily requirements of the animal during the measuring period (8 h). Glutamine and to a less extent glutamic acid were exceptions as they were taken up by the gut wall from the arterial blood. There was also a marked synthesis of ornithine and citrulline by the latter. Because of the low blood level of urea, there were no apparent exchanges of urea between the blood and the intestine; in contrast, the ammonia absorption represented about 70% of that observed after ingestion of normal protein diets. Most amino acids are largely taken up by the liver and peripheral tissues, but in the case of alanine the syntheses exceed the uptake.