Effects of intravenous infusion of high levels of potassium and sodium on mineral metabolism in sheep

A metabolism trial was conducted with 18 crossbred (Finn x Dorset x Suffolk) wethers, fitted with indwelling jugular catheters and abomasal and ileal cannulas, to determine the effects of high levels of i.v.-infused K and Na on mineral metabolism. The wethers (40 kg) were fed 800 g daily of a 60% concentrate diet in two equal portions at 0800 and 1900. Six wethers were infused randomly with 19 g K+, six with 10.6 g Na+ (chloride salts) and the other six with physiological saline solution (1.2 g Na) per day. Potassium chloride or NaCl infusion had no effects on apparent absorption, retention, flow or partial absorption of Mg, Ca and P in the digestive tract compared with physiological saline infusion. With all treatments, Mg and Ca were absorbed proximal to the abomasal cannula. Magnesium was secreted into, whereas Ca and P were absorbed from, the small intestine. Phosphorus was secreted both in the stomach and large intestinal regions of the digestive tract. Major sites of K and Na absorption were the small and large intestines, respectively. Infusion of K increased (P less than .05) retention of K compared with Na infusion. Infusion of Na increased (P less than .05) excretion and retention of Na compared with K infusion. Serum minerals were not changed by K or Na infusion compared with saline. The results of this experiment indicate that the depressing effects of K on Mg absorption are not attributable to high levels of absorbed K, but rather to K present in the digestive tract prior to the small intestine.     

妊娠母羊胆酸灌注对胎儿和新生儿的影响

妊娠期肝内胆汁淤积症(Intrahepatic cholestasis of pregnancy,ICP)是孕妇在妊娠晚期出现的以瘙痒和黄疸为特征的肝病,是一种高危产科疾病,严重影响胎儿的健康.为了更好地研究ICP的发病机制,本试验以妊娠母羊为动物模型,分别通过大剂量(2 mg/kg)和小剂量(1.1 mg/kg)的胆酸盐静脉灌注怀孕后期的母羊,同时进行胎儿血管造瘘手术,目的是研究ICP的发病模型和胆酸对胎儿和新生儿的影响机制.结果显示,给妊娠母羊大剂量多次静脉灌注胆酸盐,引起母体难产,导致胎儿宫内窘迫和死亡;小剂量灌注,导致胎儿的低出生重,但胎儿在出生后15 d时,羔羊的体质量与正常的羔羊没有差异,体现了追赶生长的特性.结果表明以妊娠母羊为动物模型,通过静脉灌注胆酸盐可以作为研究妊娠期肝内胆汁淤积症的疾病模型,为进一步探索ICP发病时胆酸对胎儿的影响机制提供实验依据.     

日粮钙水平对空怀云南半细毛羊能量代谢的影响

本文旨在通过饲养试验和消化代谢试验,以研究日粮钙水平与空怀云南半细毛羊能量代谢间可能存在的互作。试验选取50只日龄、体重和体况相近,经产两胎空怀期云南半细毛羊,随机分为5组,每组10只,分别饲喂5个钙含量分别为0.40%、0.44%、0.53%、0.65%和0.84%的日粮。进行44d饲养试验,包括14d预饲期和30d正式试验。饲养试验开始和结束各称一次体重,消化代谢试验进行5d,每天全收粪尿。结果表明:(1)0.84%Ca组、0.65%Ca组的粪能较0.44%Ca组降低18.90%、17.17%(P<0.05);代谢损失能都降低15.66%(P<0.05)。(2)0.40%Ca组、0.53%Ca组、0.84%Ca组的摄入总能较0.44%Ca组低5.11%、3.35%、4.66%(P<0.01),较0.65%Ca组高3.58%、5.50%、4.07%(P<0.01),0.44%Ca组较0.65%Ca组高9.16%(P<0.01)。(3)尿能、甲烷能、尿能占总能的比例、甲烷能占总能的比例、尿能占消化能的比例、总能消化率和总能代谢率各组间差异不显著(P>0.05)。由此可见,日粮钙水平越高,粪能和代谢损失越低,而日粮钙水平对空怀云南半细毛羊的能量代谢没有显著性影响(P>0.05)。     

Chemerin analog regulates energy metabolism in sheep

Accumulating data suggest a relationship between chemerin and energy metabolism. Our group previously described gene cloning, expression analysis and the regulatory mechanism of chemerin and its own receptor in mice and cattle. The objective of the present study was to investigate the physiological effect of chemerin on endocrine changes and energy metabolism in sheep using a biologically stable chemerin analog. The chemerin analog was intravenously administrated (100 or 500 µg/head) to sheep, and plasma insulin and metabolites (glucose, nonesterified fatty acids (NEFA), triglyceride, total cholesterol and high‐density lipoprotein (HDL) cholesterol) were analyzed. The chemerin analog dramatically increased the insulin levels, and glucose levels were decreased. NEFA levels were slightly decreased at 20 min but then increased gradually from 60 to 180 min after analog administration. In addition, injection of the chemerin analog immediately increased triglyceride and total cholesterol but not HDL levels. These results suggested that chemerin analog regulated insulin secretion related to glucose metabolism and the release of triglycerides in sheep in vivo. This study provides new information about endocrine and metabolic changes in response to chemerin in sheep.     

Effect of ruminal infusion of glucose, volatile fatty acids and hydrochloric acid on mineral metabolism in sheep

Two experiments were conducted to study the effects of alterations in ruminal pH and volatile fatty acid (VFA) concentrations on utilization of Mg and other minerals. In Exp. 1, two metabolism trials were conducted with 12 ruminally cannulated crossbred wethers fed 800 g/d of orchard-grass (Dactylis glomerata, L.) hay. After each feeding, wethers were ruminally infused with 500 ml (4.2 ml/min) or either 1) deionized water, 2) 40% (w/v) glucose solution, 3) .26 M propionic and .17 M butyric acid solution or 4) .35 M HCl. The pH of the VFA solution was adjusted to 6.8 with 10N NaOH. In Exp. 2, a metabolism trial was conducted with 12 ruminally cannulated crossbred wethers fed 600 g of orchard-grass hay and infused with a buffered VFA solution prepared as in Exp. 1 or with an unbuffered solution. In both experiments each trial consisted of a 5-d adaption period followed by four 5-d collections of feed, feces and urine. Compared with the glucose treatment, infusion of the buffered VFA solution produced similar acetic and propionic and higher (P less than .05) butyric acid concentrations (Exp. 1). The HCl solution produced changes in ruminal and pH values similar to those of the glucose infusion. In Exp. 1, apparent absorption of Mg was increased over twofold by the glucose infusion (P less than .05), but the other infusions had no effect. Apparent absorption of P was decreased (P less than .05) by HCl infusion, and K absorption was decreased by HCl and glucose infusions. In Exp. 2, infusion of the unbuffered VFA solution decreased apparent Mg absorption by 15.7%, compared with infusion of the buffered solution. These experiments suggest that the increased Mg absorption observed with carbohydrate supplementation is not due to alterations in ruminal pH or VFA levels.     

Effects of propionate infusion and dietary energy on dry matter intake in sheep

Four nonlactating, nonpregnant, mature ewes equipped with multiple venous and arterial catheters were used to evaluate the influence of propionate as a satiety signal in ruminants. Our experiment was a 4 x 4 Latin square with portal infusion (physiological saline [Sa] or sodium propionate [Pr]) and DE intake (Lo, 63% of maintenance requirement, or Hi, 200% of maintenance requirement) as factors. One 240-min infusion of Pr (1 mmol/min) or Sa into the portal vein began at approximately 0800 on d 8 of each 8-d period. Feed intake was measured and hepatic blood was sampled every 30 min during infusion. Intake of DM and digestible energy (DEI) during infusion were not affected by infusion or diet and were most rapid at 30 min postfeeding. Average 30-min DMI and DEI were 539 g and 1,484 kcal, respectively, at 240 min. Cumulative DMI and DEI were unaffected by infusion but tended to be greater with Lo. After 30 min, animals tended to consume Lo at a greater rate than Hi, suggesting that satiety was delayed. Insulin concentration was increased (P less than .02) when animals consumed Hi (36.1 mU/liter) vs Lo (16.8 mU/liter) and was elevated (P less than .01) at 30 and 60 min postfeeding when animals were infused with Pr. Plasma acetate tended to be reduced with Pr infusion. Plasma Pr tended to increase with Pr infusion, especially when sheep were fed Lo. Satiety, DMI, and DEI were not affected by Pr infusion in this study.     

The hepatic uptake of individual free fatty acids in sheep during noradrenaline infusion.

Hepatic portal and arterial blood flow and the net hepatic uptake of individual free fatty acids (FFA) were measured in sheep during intravenous infusions of saline and noradrenaline (2 mu kg-minus 1 min-minus 1). During noradrenaline infusion in FFA increased in the circulating (arterial) plasma in amounts oleate greater than palmitate greater than stearate. Changes in the hepatic uptake of FFA opposed these changes in plasma FFA composition; the hepatic uptake of oleate increased more than that of palmitate, and the uptake of stearate fell slightly, but not significantly.     

Placental transfer of etomidate in pregnant ewes after an intravenous bolus dose and continuous infusion

Etomidate (ETO) is a short-acting intravenous (IV) anaesthetic characterised by cardiopulmonary stability and favourable pharmacokinetics. Although ETO has been used satisfactorily in obstetrical anaesthesia, little is known about placental transfer and the drug's pharmacokinetics in the fetus. Placental transfer in pregnant ewes has been evaluated following the administration of an IV bolus of 1mg/kg ETO; and after a 1-h infusion of 100 microg/kg min(-1) ETO preceded by an IV bolus of 1mg/kg. In ewes, ETO concentration and AUC were higher than those found in fetuses. After the ETO bolus dose, the fetus:ewe AUC ratio was 0.45+/-0.32, and the mean residence time (MRT) was 20+/-7 min for dams and 22+/-3 min for the fetuses. After ETO infusion, the AUC ratio was 0.37+/-0.08, and MRT was 46+/-12 min for ewes and 46+/-22 min for fetuses. Although ETO crosses the placenta very rapidly and reaches the fetus in high amounts, a certain placental barrier effect limits its transfer. There is no evidence of cumulative effects of the drug in the fetus as fetal ETO elimination was as rapid as in the dam.     

Changes in fetal mannose and other carbohydrates induced by a maternal insulin infusion in pregnant sheep

Background

The importance of non-glucose carbohydrates, especially mannose and inositol, for normal development is increasingly recognized. Whether pregnancies complicated by abnormal glucose transfer to the fetus also affect the regulation of non-glucose carbohydrates is unknown. In pregnant sheep, maternal insulin infusions were used to reduce glucose supply to the fetus for both short (2-wk) and long (8-wk) durations to test the hypothesis that a maternal insulin infusion would suppress fetal mannose and inositol concentrations. We also used direct fetal insulin infusions (1-wk hyperinsulinemic-isoglycemic clamp) to determine the relative importance of fetal glucose and insulin for regulating non-glucose carbohydrates.

Results

A maternal insulin infusion resulted in lower maternal (50%, P < 0.01) and fetal (35-45%, P < 0.01) mannose concentrations, which were highly correlated (r² = 0.69, P < 0.01). A fetal insulin infusion resulted in a 50% reduction of fetal mannose (P < 0.05). Neither maternal nor fetal plasma inositol changed with exogenous insulin infusions. Additionally, maternal insulin infusion resulted in lower fetal sorbitol and fructose (P < 0.01).

Conclusions

Chronically decreased glucose supply to the fetus as well as fetal hyperinsulinemia both reduce fetal non-glucose carbohydrates. Given the role of these carbohydrates in protein glycosylation and lipid production, more research on their metabolism in pregnancies complicated by abnormal glucose metabolism is clearly warranted.     

Changes in fetal mannose and other carbohydrates induced by a maternal insulin infusion in pregnant sheep

Background: The importance of non-glucose carbohydrates, especially mannose and inositol, for normal development is increasingly recognized. Whether pregnancies complicated by abnormal glucose transfer to the fetus also affect the regulation of non-glucose carbohydrates is unknown. In pregnant sheep, maternal insulin infusions were used to reduce glucose supply to the fetus for both short(2-wk) and long(8-wk) durations to test the hypothesis that a maternal insulin infusion would suppress fetal mannose and inositol concentrations. We also used direct fetal insulin infusions(1-wk hyperinsulinemic-isoglycemic clamp) to determine the relative importance of fetal glucose and insulin for regulating non-glucose carbohydrates.Results: A maternal insulin infusion resulted in lower maternal(50%, P < 0.01) and fetal(35-45%, P < 0.01) mannose concentrations, which were highly correlated(r2= 0.69, P < 0.01). A fetal insulin infusion resulted in a 50% reduction of fetal mannose(P < 0.05). Neither maternal nor fetal plasma inositol changed with exogenous insulin infusions.Additionally, maternal insulin infusion resulted in lower fetal sorbitol and fructose(P < 0.01).Conclusions: Chronically decreased glucose supply to the fetus as well as fetal hyperinsulinemia both reduce fetal non-glucose carbohydrates. Given the role of these carbohydrates in protein glycosylation and lipid production, more research on their metabolism in pregnancies complicated by abnormal glucose metabolism is clearly warranted.     

Effect of short term starvation on disposition kinetics of chloramphenicol in goats

The effect of short term starvation on the disposition kinetics of chloramphenicol was determined in goats. The same dosage level (10 mg kg-1) administered intravenously produced higher serum concentrations in the animals when they were starved than when they were not starved. This could be attributed to the significantly smaller (P less than 0.05) volume of the central compartment. Starvation significantly decreased the rate of elimination of chloramphenicol while the apparent volume of distribution of the drug was not altered. A significant decrease in the body clearance, 1.36 +/- 0.95 ml (min kg)-1 in the starved condition compared with 3.78 +/- 2.19 mg (min kg)-1 in the controls, caused a corresponding increase in the half life of chloramphenicol. The decreased rate of elimination was attributed to decreased hepatic microsomal metabolism since starvation did not change the fraction of the dose excreted unchanged in the urine. The clinical significance of the altered disposition of chloramphenicol is that administration at the usual dosing rate would lead to accumulation of the drug and eventual toxicity.     

Effect of intraruminal butyrate infusion on the plasma insulin level in sheep

After intraruminal infusion of butyrate to sheep at dose rates of 0.25, 0.5, 1 and 2 g sodium n-butyrate per kg body mass, butyrate concentration of the rumen fluid and total secreted insulin rose in direct proportion to the butyrate dose infused. The half-life of butyrate in the rumen was always longer than that of insulin. At 90 min after the infusion of 1 g butyrate per kg body mass, butyrate concentration in the ruminal papillae reached the level corresponding to an extracellular concentration that reduced cell division by 50% in vitro. It can be concluded that butyrate may be present in the ruminal papillae in concentrations inhibiting cell proliferation, simultaneously with the presence of blood plasma insulin concentrations stimulating the proliferation of ruminal epithelial cells.     

Effect of intravenous injection of acetate on the pancreas of sheep

The effect of an intravenous injection of acetate on plasma insulin and glucagon concentration was examined in conscious sheep. Sodium acetate (312 to 5000 mumol kg-1 bodyweight) injection increased plasma insulin concentrations in a dose-dependent manner. Plasma glucagon concentration was not affected by doses up to 1250 mumol kg-1. Doses of 2500 and 5000 mumol kg-1 produced significant increases (P less than 0.05), but not in a dose related manner. The results of this study indicate that the receptive mechanism of the A cell in the sheep pancreas to acetate might be different from that of the B cell.     

Effect of cimaterol on sheep adipose tissue lipid metabolism

Effects of dietary cimaterol (5 mg/kg) on adipose tissue metabolism of wether lambs were studied. Lipogenesis, lipolysis, fatty acid composition and adipocyte size and number were measured. Cimaterol feeding increased lipogenesis; however, this effect was not statistically significant. Insulin (1,000 microU/ml) stimulated lipogenesis of adipose tissue from control sheep. However, this elevated rate was abolished by in vitro cimaterol. Insulin had no stimulatory effect on lipogenesis in cimaterol-fed sheep. Lipolysis was depressed by cimaterol feeding. However, 10(-4) M cimaterol stimulated lipolysis in the adipose tissue from both control and cimaterol-fed sheep. Insulin inhibited stimulated lipolysis in adipose tissue from control sheep but had no effect on the stimulated lipolysis in cimaterol-fed sheep. Mean adipocyte diameter was smaller (from 74 to 70 microns) and adipocyte size distribution also was changed in the cimaterol-fed sheep. Adipocyte number per gram of tissue was not affected by cimaterol. There was a significant increase in percentage of unsaturated fatty acids in adipose tissue from cimaterol-fed sheep. These results indicate that lipogenic and lipolytic responses to insulin and cimaterol in sheep adipose tissue were altered by cimaterol feeding. The carcass fat content decrease in cimaterol-fed sheep may be attributed to the reduction in adipocyte size.