Metabolic clearance rate of adrenocorticotropin in the rat.
The metabolic clearance rate (MCR) of adrenocorticotropin (ACTH) was estimated after the intravenous infusion of graded rates of the hormone (40-2560 muU/min per 100 g body weight) in rats pretreated with chlorpromazine, morphine, and Nembutal, a preparation which proved effective in blocking endogenous ACTH release. The hormone was infused over a period of 45 min, at which time the plasma ACTH concentration had reached a steady state. A specific and sensitive bioassay, based on the corticosterone production of dispersed adrenal cells, was used to measure the plasma ACTH concentration. With increasing infusion rates of ACTH, a threefold decrease in the MCR of ACTH was observed. Previous studies of our group have shown that the MCR of corticosterone increases as a function of the infusion rate of the steroid. It appears, therefore, that the metabolism of these two hormonal links of the hypothalamo-pituitary-adrenocortical axis vary in opposite fashions as a function of the secretion rate of the hormone.
D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001681:Biological Assay; D003345:Corticosterone / Q000097:blood; D008297:Male; D008657:Metabolic Clearance Rate; D051381:Rats
D000324:Adrenocorticotropic Hormone; D003345:Corticosterone