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- Author or Editor: Jan A. Mol x
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Summary
In 6 cats, the effect of iv administration of various concentrations of ovine corticotropin-releasing hormone (ocrh) on plasma concentrations of cortisol, α-melanocyte-stimulating hormone (α-msh), and adrenocorticotropic hormone (acth) was measured. After administration of 1.0 μg of ocrh/kg of body weight, significant (P < 0.05) increases in plasma cortisol, α-msh, and acth concentrations were observed. After administration of 0.1 μg of ocrh/kg, significant increases were found only for cortisol and acth concentrations.
In vitro release of acth from dispersed feline pars distalis cells in primary culture stimulated by ocrh and arginine vasopressin (avp) was dose-dependent. Maximal stimulation was achieved by 1 nM ocrh or 100 nM avp. The ocrh-stimulated acth release was partially inhibited by dexamethasone, and avp-induced release was completely inhibited. Pars intermedia cells released 20 times as much α-msh as acth. A dose-dependent inhibition of α-msh release was induced by the dopamine agonist, bromocriptine. This inhibition could be partially abolished by coincubation with haloperidol. Bromocriptine had no effect on release of acth.
In conclusion, ocrh stimulates the pars distalis and pars intermedia of the pituitary gland of cats. Release of acth is stimulated by a direct effect on the pars distalis. In addition, in cats, ocrh is a more potent secretagogue than is avp. The msh release from the pars intermedia is sensitive to dopaminergic inhibition, indicating that dopamine may have a central role in regulation of msh secretion in cats.
Abstract
Objective—To determine plasma concentrations of adrenocorticotrophic hormone (ACTH) and α-melanocyte stimulating-hormone (α-MSH) in healthyferrets and ferrets with hyperadrenocorticism.
Animals—16 healthy, neutered, privately owned ferrets, 28 healthy laboratory ferrets (21 sexually intact and 7 neutered), and 28 ferrets with hyperadrenocorticism.
Procedures—Healthy ferrets were used for determination of reference plasma concentrations of ACTH and α-MSH. Diagnosis of hyperadrenocorticism was made on the basis of history, clinical signs, urinary corticoid-to-creatinine ratios, ultrasonography of the adrenal glands, and macroscopic or microscopic evaluation of the adrenal glands. Blood samples were collected during isoflurane anesthesia. Plasma concentrations of ACTH and α-MSH were measured by radioimmunoassay.
Results—Plasma concentrations of ACTH in 23 healthy neutered ferrets during the breeding season ranged from 4 to 145 ng/L (median, 50 ng/L). Plasma concentrations of α-MSH in 44 healthy neutered or sexually intact ferrets during the breeding season ranged from < 5 to 617 ng/L (median, 37 ng/L). Reference values (the central 95% of the values) for ACTH and α-MSH were 13 to 100 ng/L and 8 to 180 ng/L, respectively. Plasma concentrations of ACTH and α-MSH in ferrets with hyperadrenocorticism ranged from 1 to 265 ng/L (median, 45 ng/L) and 10 to 148 ng/L (median, 46 ng/L), respectively. These values were not significantly different from those of healthy ferrets. Plasma ACTH concentrations of sexually intact female ferrets in estrus were significantly higher than those of neutered females.
Conclusions and Clinical Relevance—Ferrets with hyperadrenocorticism did not have detectable abnormalities in plasma concentrations of ACTH or α-MSH. The findings suggest that hyperadrenocorticism in ferrets is an ACTH and α-MSH-independent condition.—(Am J Vet Res 2002;63:1395–1399)
SUMMARY
In 6 cats, mean ± sem baseline plasma concentrations of cortisol, corticotropin, and α-melanocyte-stimulating hormone (α-msh) were 87 ± 16 nmol/ L, 73 ± 14 ng/L, and 129 ± 12 ng/L, respectively. The cats were subjected to: handling and subsequent skin testing without anesthesia; anesthesia with 50 mg of ketamine HCl and 2.5 mg of diazepam given IV, immediately followed by handling and skin testing; and anesthesia and handling as previously described, but without skin testing. Significant (P <0.05; multivariate analysis for repeated measures) increase in plasma cortisol, corticotropin, and α-msh concentrations was observed until 20 minutes after the start of the experiments in cats undergoing physical restraint and subsequent skin testing with or without preceding anesthesia. These responses were largely abolished when anesthesia with ketamine and diazepam was only followed by handling.
We conclude that, during stress in cats (in contrast to dogs), the pituitary intermediate lobe is activated to secrete α-msh. In addition, the cortisol response after skin testing of cats under anesthesia may be a reasonable explanation for the reported weak skin test reactivity in cats.
Abstract
Objective—To evaluate plasma concentrations of growth hormone (GH) and insulin-like growth factor I (IGF-I) in healthy dogs and large-breed dogs with dilated cardiomyopathy (DCM).
Animals—8 dogs with DCM and 8 healthy control dogs of comparable age and body weight.
Procedures—Blood samples for determination of the pulsatile plasma GH profile were collected from all dogs at 10-minute intervals between 8:00 am and 8:00 pm. Plasma IGF-I concentration was determined in the blood sample collected at 8:00 am.
Results—No significant differences in plasma IGF-I concentrations, basal plasma GH concentration, GH pulse frequency, area under the curve above the zero line and above the baseline for GH, and GH pulse amplitude were found between dogs with DCM and control dogs.
Conclusions and Clinical Relevance—Results did not provide evidence for an association between DCM in dogs and a reduction in plasma concentrations of GH or IGF-I. Therefore, reported positive effects of GH administration are most likely attributable to local effects in the heart.
Abstract
Objective—To investigate the physiologic endocrine effects of food intake and food withholding via measurement of the circulating concentrations of acylated ghrelin, growth hormone (GH), insulin–like growth factor-I (IGF-I), glucose, and insulin when food was administered at the usual time, after 1 day's withholding, after 3 days' withholding and after refeeding the next day in healthy Beagles.
Animals—9 healthy Beagles.
Procedures—Blood samples were collected from 8:30 AM to 5 PM from Beagles when food was administered as usual at 10 AM, after 1 day's withholding, after 3 days' withholding, and after refeeding at 10 AM the next day.
Results—Overall mean plasma ghrelin concentrations were significantly lower when food was administered than after food withholding. Overall mean plasma GH and IGF-I concentrations did not differ significantly among the 4 periods. Circulating overall mean glucose and insulin concentrations were significantly higher after refeeding, compared with the 3 other periods.
Conclusions and Clinical Relevance—In dogs, food withholding and food intake were associated with higher and lower circulating ghrelin concentrations, respectively, suggesting that, in dogs, ghrelin participates in the control of feeding behavior and energy homeostasis. Changes in plasma ghrelin concentrations were not associated with similar changes in plasma GH concentrations, whereas insulin and glucose concentrations appeared to change reciprocally with the ghrelin concentrations.
