Effects of bromocriptine on corticotrophin, melanotrophin and corticosteroid secretion in dogs with pituitary-dependent hyperadrenocorticism.
Dogs with spontaneous pituitary-dependent hyperadrenocorticism were divided into two groups, one with normal plasma concentrations of alpha-MSH (normal alpha-MSH dogs, n = 26) and the other with high plasma concentrations of alpha-MSH (high alpha-MSH dogs, n = 14), on the presumption that high alpha-MSH concentrations indicated a parent cell of pars intermedia origin. The urinary corticoid/creatinine ratios of the high alpha-MSH dogs were significantly higher than those of the normal alpha-MSH dogs. The percentage decrease of the corticoid/creatinine ratios following dexamethasone administration was significantly higher in the normal alpha-MSH dogs than in the high alpha-MSH dogs. Dexamethasone resistance occurred in both the normal alpha-MSH dogs (4 out of 26) and the high alpha-MSH dogs (7 out of 14), indicating a relative rather than an absolute difference. The short-term effect of orally administered bromocriptine, at a dose (10 micrograms/kg body weight) known to be effective in lowering prolactin concentrations in dogs, was investigated by measuring concentrations of cortisol, ACTH and alpha-MSH in plasma at 4, 6 and 8 h after administration. Significant decreases were observed for cortisol in both groups and for alpha-MSH only in the high alpha-MSH dogs. The effect of 5 days of bromocriptine administration (10 micrograms at 12-h intervals) was assessed by measurements of urinary corticoid/creatinine ratios. Considering both groups as a whole, only the corticoid/creatinine ratios of the high alpha-MSH dogs decreased significantly on the first day of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Rijnberk
A
A
Small Animal Clinic, Faculty of Veterinary Medicine, State University, Utrecht, The Netherlands.
Mol
J A
JA
Kwant
M M
MM
Croughs
R J
RJ
D000305:Adrenal Cortex Hormones / Q000097:blood*; D000308:Adrenocortical Hyperfunction / Q000503:physiopathology*; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D013997:Time Factors; D000521:alpha-MSH / Q000097:blood*
D000305:Adrenal Cortex Hormones; D001971:Bromocriptine; D000521:alpha-MSH; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone