Effect of cranial sympathectomy on circadian rhythms of cortisol, adrenocorticotropic hormone and melatonin in boars

Following weaning at 24 +/- 1 d of age, crossbred boars were subjected to removal of the cranial cervical ganglia (GX, n = 8) or sham surgery (SHAM, n = 8). At 213 +/- 1 d of age, a catheter was inserted into a jugular vein or vena cava, and all boars were housed in environmentally controlled rooms at 22 degrees C with an equatorial photoperiod. After 2 wk of exposure to this photic environment, samples of plasma and serum were collected at hourly intervals for 24 h. The plasma was assayed for adrenocorticotropic hormone (ACTH) and the serum was assayed for cortisol and melatonin by RIA. The time-trends for all three hormones were described by regression models, which were tested for heterogeneity of regression between SHAM and GX treatments. The circadian rhythm of cortisol in serum was similar for SHAM and GX treatments. The profiles of ACTH were also similar between the two treatments, but circadian changes in concentrations of ACTH paralleling those of cortisol were not evident in either treatment. Overall, concentrations of ACTH were reduced (P = .06) for GX boars compared to SHAM boars. The time-trends of melatonin in serum differed (P less than .001) for GX and SHAM treatments, with a nocturnal rise in melatonin evident in some SHAM boars but not in GX animals. Four SHAM boars had profiles of melatonin that obviously entrained to the light-dark cycle. None of the boars in GX treatment had elevated concentrations of melatonin in serum during the dark period, relative to concentrations during the light.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of light intensity on circadian profiles of melatonin, prolactin, ACTH, and cortisol in pigs.

Eleven crossbred barrows were housed in environmentally controlled rooms with an 8-h photoperiod. Pigs in one room received control illumination of 113 1x (CON; n = 6), and pigs in the other room received intense illumination of 1,783 1x (INT; n = 5) fluorescent light. Pigs were given at least 20 d of exposure to the environment before blood samples were taken every 3 h for 48 h. Data were analyzed by split-plot analysis of variance. Except for prolactin, no treatment x time interactions were noted for the hormone profiles evaluated (P greater than .10). Pigs in INT had greater (P less than .05) concentrations of prolactin in serum than pigs in CON at every sampling time. Concentrations of ACTH and cortisol in plasma were similar for INT (33.9 +/- 3.2 pg/mL of ACTH and 24.4 +/- 3.4 ng/mL of cortisol, respectively) and CON (34.9 +/- 3.0 pg/mL of ACTH and 31.3 +/- 3.1 ng/mL of cortisol, respectively). Within the INT treatment, serum melatonin concentrations were more than doubled (P less than .05) during darkness (66.8 +/- 9.3 pg/mL) compared with during light (30.4 +/- 9.3 pg/mL); however, within the CON treatment, concentrations during light and darkness did not differ (38.4 +/- 9.3 pg/mL and 42.9 +/- 9.3 pg/mL, respectively). Results indicate that light of greater intensity is required to entrain circadian rhythms of melatonin in serum of pigs. Furthermore, pigs may respond to bright light with greater secretion of prolactin, even under constant duration of photoperiod.     

The effect of active immunization against adrenocorticotropic hormone on cortisol, beta-endorphin, vocalization, and growth in pigs

Because the poor growth performance of intensively housed pigs is associated with increased circulating glucocorticoid concentrations, we investigated the effects of glucocorticoid suppression by inducing a humoral immune response to ACTH on physiological and production variables in growing pigs. Grower pigs (28.6 +/- 0.9 kg) were immunized with amino acids 1 through 24 of ACTH conjugated to ovalbumin and suspended in diethylaminoethyl (DEAE) dextran-adjuvant or adjuvant alone (control) on d 1, 28, and 56. The ACTH-specific antibody titers generated suppressed increases in cortisol concentrations on d 63 in response to an acute stressor (P = 0.002; control = 71 +/- 8.2 ng/mL; ACTH-immune = 43 +/- 4.9 ng/mL) without altering basal concentrations. Plasma beta-endorphin concentrations were also increased (P < 0.001) on d 63 (control = 18 +/- 2.1 ng/mL; ACTH-immune = 63 +/- 7.3 ng/mL), presumably because of a release from negative feedback on the expression of proopiomelanocortin in pituitary corticotropes. Immunization against ACTH did not alter ADG (P = 0.120; control = 1,077 +/- 25; ACTH-immune = 1,143 +/- 25 g) or ADFI (P = 0.64; control = 2,719 +/- 42; ACTH-immune = 2,749 +/- 42 g) and did not modify behavior (P = 0.681) assessed by measuring vocalization in response to acute restraint. In summary, suppression of stress-induced cortisol responses through ACTH immunization increased beta-endorphin concentrations, but it did not modify ADG, ADFI, or restraint vocalization score in growing pigs.     

Use of compounded adrenocorticotropic hormone (ACTH) for adrenal function testing in dogs

Serum cortisol concentrations were measured in five healthy dogs in response to five adrenocorticotropic hormone (ACTH) preparations. Cortisol concentrations were similar at time 0 (pre-ACTH) and at 30 and 60 minutes after injection of all forms of ACTH. However, at 90 and 120 minutes post-ACTH, serum cortisol concentrations were significantly lower following injection of two compounded forms of ACTH. The data showed that injection of four compounded forms of ACTH caused elevations in serum cortisol concentrations of a similar magnitude as cosyntropin in samples collected 60 minutes after administration; but concentrations at later times varied, depending on the type of ACTH used.     

Technical note: effect of corticotropin-releasing hormone on adrenocorticotropic hormone and cortisol in steers

The objective of this study was to determine an appropriate exogenous dose of bovine corticotropin-releasing hormone (bCRH) to stimulate the physiological effects of the hypothalamic-pituitary-adrenal axis in steers as a method to test the sensitivity of the pituitary and adrenal gland. Twenty 14-mo-old Holstein-Friesian steers were blocked by weight (443.7+/-2.5 kg) and randomly allotted to receive either saline (control) or bCRH (0.1, 0.3, 1.0, or 1.5 microg/kg BW). Animals were housed in a slatted-floor facility (n = 5 per pen). Indwelling jugular catheters, for both the administration of bCRH and blood collection, were fitted on d -1 of the experiment. Saline and bCRH were administered i.v. at time 0. Serial blood samples were collected at -15, 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, and 180 min relative to time 0. Following administration of 0.1 microg of bCRH/kg BW, the peak ACTH response was not significantly different from pretreatment baseline concentrations (mean concentrations as measured at -15 and 0 min before bCRH administration). Mean ACTH concentrations from 0 to 180 min following 0.1 microg of bCRH/kg BW were not significantly different (P = 0.177) from controls. Administration of 0.3, 1.0, and 1.5 microg of bCRH/kg BW increased (P < 0.05) peak ACTH above pretreatment concentrations, and mean ACTH from 0 to 180 min for these treatments were greater (P < 0.05) than for controls. Peak cortisol responses to all bCRH treatments were greater (P < 0.05) than those to pretreatment concentrations. Mean cortisol concentrations from 0 to 180 min were greater (P < 0.05) in all bCRH-treated steers than in controls, but there were no significant differences among the bCRH treatments. The ratio of mean cortisol to mean ACTH for all bCRH doses tested differed (P < 0.05) from control values, indicating reactivity of the adrenals. In conclusion, bCRH challenge may be a useful method for testing the sensitivity of the hypothalamic-pituitary-adrenal axis in steers subjected to stressful husbandry conditions, and a minimum dose of 0.3 microg of bCRH/kg BW is required to stimulate physiological effects of stressor hormones.     

Effects of adrenocorticotropic hormone challenge and age on hair cortisol concentrations in dairy cattle

Dairy cattle suffer stress from management and production; contemporary farming tries to improve animal welfare and reduce stress. Therefore, the assessment of long-term hypothalamic-pituitary-adrenal function using non-invasive techniques is useful. The aims in this study were: to measure cortisol concentration in cow and calves hair by radioimmunoassay (RIA), to test cortisol accumulation in bovine hair after adrenocorticotropic hormone (ACTH) challenges, and determine the influence of hair color on cortisol concentrations. Fifteen Holstein heifers were allotted to 3 groups (n = 5 each): in control group (C), just the hair was sampled; in the saline solution group (SS), IV saline solution was administered on days 0, 7, and 14; and the ACTH group was challenged 3 times with ACTH (0.15 UI per kg of body weight) on days 0, 7, and 14. Serum samples from the SS and ACTH groups were obtained 0, 60 and 90 min post-injection. Serum cortisol concentration was greater 60 and 90 min after injection with ACTH. Hair was clipped on days 0, 14, 28, and 44. Hair cortisol was methanol extracted and measured by RIA. Hair cortisol was preserved for 11 mo. Hair cortisol concentrations in the ACTH group were greater than in the saline and control groups on days 14 and 28, but not on day 44. Concentrations were greater in calves than in cows and greater in white hair than in black hair. Cortisol accumulated in bovine hair after ACTH challenges, but the concentration was affected by both age and hair color. If hair color effects are taken into account, assessing cortisol concentration in hair is a potentially useful non-invasive method for assessing stress in cattle.     

Effects of androgen on plasma levels of adrenocorticotropic hormone and cortisol during transportation in goats

Previously, we demonstrated that plasma cortisol (Cor) levels were increased by road transportation in castrated male goats, but the extent of the increase was significantly reduced by 5alpha-dihydrotestosterone (DHT) implantation. This study aims to clarify whether the reduction of Cor secretion by androgen during transportation results from reduced plasma adrenocorticotropic hormone (ACTH). Castrated goats were implanted separately with cholesterol (Cho), testosterone (T) or DHT, followed by transportation. Plasma Cor levels increased during transportation regardless of hormone treatment, but the levels in T and DHT treated animals were lower than those in animals treated with Cho. Plasma ACTH levels also increased during transportation, and those in T treated animals were significantly lower than in those treated with Cho. However, plasma ACTH levels in DHT treated animals varied among the animals and did not differ from those in Cho treated animals. Significant and highly positive correlations between the logarithm of plasma ACTH levels and plasma Cor levels were found in every treatment group. The areas under the regression curves between plasma ACTH levels and plasma Cor levels associated with T and DHT treatments were significantly lower than those with Cho treatment. In conclusion, T was shown to reduce ACTH secretion in response to transportation in castrated goats. However, this suppression of the increase in Cor secretion during transportation by androgen is suggested to be mainly a result of suppression of the responsiveness of the adrenal cortex to ACTH.     

Plasma cortisol and progesterone responses to low doses of adrenocorticotropic hormone in ovariectmized lactating cows

The objective of this study was to describe the responses of the plasma progesterone and cortisol concentrations in ovariectomized lactating cows to low doses of adrenocorticotropic hormone (ACTH). The estrous cycles in 3 lactating cows were synchronized, and the cows were ovariectomized in the luteal phase. ACTH challenge tests were conducted at doses of 3, 6, 12 and 25 IU. Blood samples were collected at 30 min intervals, and the plasma progesterone and cortisol concentrations were analyzed by EIA. A concomitant rise in plasma progesterone and plasma cortisol was observed in cows treated with 12 IU or higher doses of ACTH. Significant increments in the plasma cortisol concentrations were observed at all doses of ACTH. The means (+/- SE) of the peak plasma progesterone concentrations after the 3, 6, 12 and 25 IU ACTH challenge tests were 0.6 +/- 0.1, 1.3 +/- 0.4, 1.5 +/- 0.3 and 2.4 +/- 0.3 ng/ml, respectively. The means of the peak plasma cortisol concentrations in the 3 cows after the ACTH challenge were 14.0 +/- 1.5, 17.0 +/- 2.5, 23.3 +/- 3.0, and 33.3 +/- 7.0 ng/ml, respectively. The effects of the doses, time after treatment, and their interaction on the plasma progesterone concentrations after the ACTH challenge were significant (P<0.01). Likewise, the effects of the doses, time after treatment, and their interaction on the plasma cortisol concentrations after the ACTH challenge were significant (P<0.01). The mean AUC values for the plasma progesterone and cortisol concentrations after the ACTH treatments were also significantly affected by the dose of ACTH (P<0.01 and P<0.05, respectively). A significantly positive correlation was obtained between the peak plasma progesterone and cortisol concentrations after different doses of ACTH (r=0.7, P<0.05). The results suggest that lactating dairy cows are capable of secreting a significant amount of adrenal progesterone, reaching up to the minimal concentration necessary to cause suppression of estrus in response to 12 IU ACTH (P<0.01). The concomitant plasma cortisol concentration was 23.3 ng/ml.     

Effect of whole-body vibration in the vertical axis on cortisol and adrenocorticotropic hormone levels in piglets

Vibration, being a consequence of motion during transport, may impair the welfare of pigs. Therefore, the primary objectives of this study were 1) to evaluate during transport simulation the use of ACTH and cortisol plasma levels, which are part of a basic adaptation mechanism of pigs and 2) to define comfort conditions for pigs related to the frequency and acceleration of vibration. Pigs with a body weight between 20 and 25 kg were vibrated in the vertical direction for 2 h at 2, 4, 8, and 18 Hz, in combination with root mean square acceleration magnitudes of 1 or 3 m/s2. Blood was sampled at regular intervals before, during, and after vibration as the pig's behaviors were recorded. Data on ACTH, cortisol, and behavior could be collected from 104 vibrated pigs and 21 controls. In addition, eight animals (3 controls, 5 vibrated) were treated with 0.1 mg of dexamethasone/kg BW, eight animals (3 controls, 8 vibrated) with 0.1 mg naloxone/kg BW, and six (2 controls, 4 vibrated) with a physiological salt solution. Blood samples were taken and products were administrated via an intravenous catheter. The pigs spent less time lying during both hours of vibration treatment than during control conditions. Compared with 2 and 4 Hz, time spent lying was 10 times shorter at 8 Hz and 18 times shorter at 18 Hz. At 1030, ACTH levels were significantly higher than basal levels in animals vibrated at 2 (P < 0.0001), 4 (P < 0.002), and 18 Hz (P < 0.0006). After 1 h, levels returned to basal values. Cortisol levels increased very rapidly after the beginning of vibration (P < 0.0001) and remained higher until 1 h after cessation of vibration (P < 0.003). An inferrence of the lines of equal responses for ACTH and cortisol indicated that, in the beginning of vibration exposure, pigs were extremely susceptible to vibrations at lower frequencies (2 and 4 Hz), whereas at the end of vibration exposure the responses were higher at 18 Hz. The application of dexamethasone and naloxone underpinned the emotional component of the response strategy of pigs to vibration. Hence, vibration during transport should be minimized in order to enhance the adaptive capacities of pigs.     

Effect of administration of adrenocorticotropic hormone on plasma concentrations of testosterone, luteinizing hormone, follicle stimulating hormone and cortisol in stallions

In boars and rabbits, administration of adrenocorticotropic hormone (ACTH) results in a testis-dependent, short-term increase in concentrations of testosterone in peripheral plasma. This experiment was designed to assess the short-term effects of a single ACTH injection on plasma concentrations of testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH) and cortisol in stallions. Eight light horse and two pony stallions were paired by age and weight and then one of each pair was randomly assigned to the treatment (ACTH, .2 IU/kg of body weight) or control (vehicle) group. Injection of ACTH increased (P<.01) plasma concentrations of cortisol by approximately twofold in the first 60 minutes; control stallions showed no change (P>.10) in concentrations of cortisol during the blood sampling period. Control stallions exhibited a midday increase (P>.05) in concentrations of testosterone similar to that reported previously; ACTH treatment prevented or delayed this increase such that concentrations of testosterone in treated stallions were lower (P<.05) than in controls 4 to 5 hours after injection of ACTH. Treatment with ACTH had no effect (P<.10) on plasma concentrations of LH or FSH up to 12 hours after injection.     

Comparison between blood serum and salivary cortisol concentrations in horses using an adrenocorticotropic hormone challenge

Reasons for performing study: In horses, serum cortisol concentration is considered to provide an indirect measurement of stress. However, it includes both free and bound fractions. The sampling method is also invasive and often stressful. This is not the case for salivary cortisol, which is collected using a more welfare‐friendly method and represents a part of the free cortisol fraction, which is the biologically active form. Objectives: To compare salivary and serum cortisol assays in horses, in a wide range of concentrations, using an adrenocorticotropic hormone (ACTH) stimulation test, in order to validate salivary cortisol for stress assessment in horse. Methods: In 5 horses, blood samples were drawn using an i.v. catheter. Saliva samples were taken using swabs. Cortisol was assayed by radioimmunoassay. All data were treated with a regression method, which pools and analyses data from multiple subjects for linear analysis. Results: Mean ± s.d. cortisol concentrations measured at rest were 188.81 ± 51.46 nmol/l in serum and 1.19 ± 0.54 nmol/l in saliva. They started increasing immediately after ACTH injection and peaks were reached after 96 ± 16.7 min in serum (356.98 ± 55.29 nmol/l) and after 124 ± 8.9 min in saliva (21.79 ± 7.74 nmol/l, P<0.05). Discharge percentages were also different (225% in serum and 2150% in saliva, P<0.05). Correlation between serum and salivary cortisol concentrations showed an adjusted r²= 0.80 (P<0.001). The strong link between serum and salivary cortisol concentrations was also estimated by a regression analysis. Conclusions: The reliability of both RIAs and regression found between serum and salivary cortisol concentrations permits the validation of saliva‐sampling as a noninvasive technique for cortisol level assessment in horses.     

Plasma renin activity and plasma concentrations of aldosterone, cortisol, adrenocorticotropic hormone, and alpha-melanocyte-stimulating hormone in healthy cats

A pathogenetic role of the renin-angiotensin-aldosterone system has been implicated in cats in both systemic arterial hypertension and hypokalemic myopathy. Yet, measurement of plasma aldosterone concentrations (PACs) and plasma renin activity (PRA) has not unequivocally pointed to hyperaldosteronism as a cause of these conditions. To obtain appropriate reference ranges, this study included a large number (130) of healthy house cats of different breeds without a history of recent illness and plasma concentrations of urea and creatinine below the upper limit of the respective reference ranges. In addition, the pituitary-adrenocortical axis was studied by measuring plasma concentrations of adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), and cortisol. Reference ranges for PACs (110-540 pmol/L; 40-195 pg/mL), PRA (60-630 fmol/L/s; 0.3-3 ng/mL/h), and the aldosterone to renin ratio (ARR) (0.3-3.8) were very similar to those established in the same laboratory for humans in a supine position. No breed differences were found. The ARRs in neutered cats were significantly higher than in intact cats, primarily because of low PRA in neutered cats. The ARRs of cats > or = 5 years of age were significantly higher than those of cats < 5 years of age. The plasma concentrations of ACTH, alpha-MSH, and cortisol did not correlate significantly with PAC. Thus, although blood sampling was performed in cats in nonstandardized positions and was associated with a wide variation of stress responses, the references ranges of PAC, PRA, and ARR were similar to the relatively narrow limits established for humans under standardized conditions. The effects of neutering and aging on PRA and ARR warrant further investigation.     

The sympatho-adrenal system and plasma levels of adrenocorticotropic hormone, cortisol and catecholamines in equine grass sickness

Plasma levels of adrenocorticotropic hormone (ACTH), cortisol and catecholamines were used to study the role of the sympatho-adrenal system in equine grass sickness. Statistical evaluation determined differences of hormone levels between seven horses with grass sickness (one acute, five subacute and one chronic), six horses with colic (one with laminitis) and 16 control horses before and after mild stress. Plasma levels of the hormones were higher in horses with acute and subacute grass sickness than in the other groups. No differences were detected between horses with colic and stressed control horses but some hormone levels differed between control and colic horses and control horses before and after stress. It is possible that hyperactivation of the sympatho-adrenal system is caused by stress but it is uncertain whether the stress is only a result of the severity of the disease or also plays a role in its aetiology.     

Adrenocorticotropic hormone and cortisol in calves after corticotropin-releasing hormone.

The aim for this study was to analyze responsiveness of the hypothalamo-pituitary-adrenocortical axis to exogenous bovine corticotropin-releasing hormone (bCRH) in calves. Two dose-response studies were carried out, using either bCRH alone (dose rates of 0, .01, .03, and .1 microg bCRH/kg live weight) or in combination with arginine-vasopressin (bCRH:AVP, 0:0, .1:.05, .5:.25, and 1:.5 microg kg live weight). The bCRH was administered i.v. to calves (n = 5 to 7 per dose) housed individually or in groups. Serial blood samples were obtained from before to 300 min after injection and analyzed for plasma ACTH and cortisol concentrations. The lowest bCRH dose that produced a response in all calves was .1 microg/kg. In the experiment using bCRH with AVP, increasing the bCRH dose from .1 to 1 microg/kg resulted in an increase in peak ACTH concentration (321 vs. 2,003 pg/mL) but did not significantly affect the peak cortisol concentration (37 vs. 40 ng/mL). The time to reach the peak cortisol concentration increased with the dose of bCRH with AVP (from 38 to 111 min). The ACTH and cortisol concentrations determined at any time between 20 and 90 min after bCRH injection were correlated to the integrated responses calculated as areas under the ACTH and the cortisol curves (r between .61 and .99, P<.05). In comparison with results from studies in humans, pigs, and sheep, our data showed that the pituitary of calves seems less sensitive to CRH than that of other mammals, despite a greater capacity to produce ACTH. Moreover, the calf's adrenals seem to have a lower capacity to produce cortisol than adrenals of other mammals. As in other species, it seems that AVP enhances the release of ACTH and cortisol. For CRH challenge to be used in calves, we suggest injecting at least .1 microg of bCRH/kg live weight either with or without AVP and taking several blood samples before injection and between 20 and 90 min after injection.     

Salivary cortisol in pigs following adrenocorticotrophic hormone stimulation: comparison with plasma levels

Four prepubertal pigs were prepared with venous catheters and housed in metabolism cages. Plasma and saliva samples were taken at 15-min intervals over a 105-min period and analysed by radioimmunoassay for total (i.e. free and bound) cortisol content. Adrenocorticotrophic hormone (ACTH) was given i.v. at three different doses (0.5, 1.0 and 2.0 mg) after the second sample and the cortisol responses were compared with pretreatment values and levels observed after saline vehicle administration. Basal levels of salivary cortisol were approximately 10% of those in plasma. ACTH induced significant increases in plasma and salivary cortisol but in no case was a dose/response relationship detected. Plasma cortisol showed a maximum increase of approximately 230% whereas salivary cortisol increased only by about 130%, indicating that salivary cortisol is a less sensitive indicator of adrenal activity than plasma cortisol in this species. Estimation of salivary cortisol concentrations may offer practical advantages for the assessment of stress responses in intensively housed pigs.     

Influence of exogenous adrenocorticotropic hormone on estrous behavior in cattle.

A two-trial experiment was conducted to determine the influence of ACTH on estrous behavior in cattle. In Trial 1, Holstein heifers (n = 20) received an injection of prostaglandin F2 alpha (PGF) during a synchronized diestrus and 30 h later were allotted randomly to receive (i.m.) either 1) 4 mL of gelatin (Veh) or 2) 320 units of ACTH in 4 mL of gelatin (ACTH). Eleven days after the PGF injection, all heifers were again injected with PGF, and they received either Veh or ACTH to complete a cross-over design. Treatment with ACTH decreased (P less than .05) the duration of estrus (12.0 +/- 1.9 vs 18.0 +/- 1.6 h for Veh) and increased (P less than .001) the interval to estrus after PGF injection (62.9 +/- 2.6 vs 43.7 +/- 2.2 h for Veh). Peak serum concentrations of progesterone (P4) and cortisol (C) were elevated (P less than .001) after ACTH compared with Veh. In Trial 2, ovariectomized Holstein cows (n = 12) were injected (i.m.) with .5 mg of estradiol benzoate (EB) and, 10 h later, were allotted randomly to receive (i.m.) either 1) 4 mL of gelatin (Veh) or 2) 320 units of ACTH in 4 mL of gelatin (ACTH). Seven days after the initial EB injection, all cows were again injected with .5 mg of EB and, 10 h later, received either Veh or ACTH to complete a cross-over design. Treatment with ACTH decreased (P less than .01) the proportion of cows in estrus (2/12 vs 11/12 for Veh) and increased (P less than .01) peak serum concentrations of P4 and C.(ABSTRACT TRUNCATED AT 250 WORDS)