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Control of adrenocorticotropin secretion and adrenocortical sensitivity in neurohypophysectomized conscious dogs: effects of acute and chronic vasopressin replacement. Endocrinology 1988 Apr;122(4):1410-8

Date

04/01/1988

Pubmed ID

2831029

DOI

10.1210/endo-122-4-1410

Scopus ID

2-s2.0-0023903554   21 Citations

Abstract

We examined the effect of neurohypophysectomy with and without vasopressin replacement on the ACTH response to hypotension and ovine CRF infusion and on the adrenocortical response to ACTH and angiotensin II infusion in conscious dogs. Nitroprusside hypotension (decrease in mean arterial pressure of 25 mm Hg) in the intact state resulted in large increases in plasma arginine vasopressin (pAVP; from 2.6 +/- 0.3 to 296 +/- 63 pg/ml) and ACTH (from 35 +/- 6 to 395 +/- 92 pg/ml). Neurohypophysectomy resulted in greatly attenuated pAVP (8.4 +/- 1.6 pg/ml) and ACTH (80 +/- 10 pg/ml) responses to hypotension which were not normalized by physiological low dose vasopressin replacement (6-18 pg/kg.min continuously, iv, for 2 weeks). However, acute administration of vasopressin (4-6 ng/kg.min) simultaneously with hypotension in the neurohypophysectomized (neurohypox) dog, which produced pAVP levels equivalent to the hypotensive response to intact dogs, almost completely normalized the ACTH response to hypotension (to 248 +/- 74 pg/ml). The ACTH response to 20 ng/kg.min ovine CRF, iv (from 43 +/- 8 to 268 +/- 77 pg/ml), was not attenuated by neurohypophysectomy. The cortisol responses to infusion of 0.5 and 2 ng/kg.min ACTH-(1-24), iv, were essentially normal in neurohypox dogs. However, the ACTH and aldosterone responses to 5 ng/kg.min angiotensin II infusion iv were attenuated in neurohypox dogs off AVP replacement. Histological examination revealed normal adrenal glands and anterior pituitaries in neurohypox dogs. Immunocytochemical staining for vasopressin and neurophysin revealed normal cell bodies in the paraventricular and supraoptic nuclei of the hypothalami from neurohypox dogs. However, median eminence staining for AVP and neurophysin was greatly diminished in neurohypox dogs. In summary, neurohypophysectomy 1) attenuated the ACTH response to hypotension and angiotensin II, but not to CRF, and 2) attenuated the aldosterone response to high dose angiotensin II. Furthermore, the deficit in ACTH secretion was almost completely normalized by increasing plasma AVP levels to those observed in the intact dogs. We conclude that an action of circulating pAVP increases ACTH secretion by a direct effect at the pituitary and by activating afferent input to the hypothalamus.

Author List

Raff H, Merrill DC, Skelton MM, Brownfield MS, Cowley AW Jr

Authors

Allen W. Cowley Jr PhD Professor in the Physiology department at Medical College of Wisconsin
Hershel Raff PhD Professor in the Medicine department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Adrenal Cortex
Adrenocorticotropic Hormone
Aldosterone
Animals
Arginine Vasopressin
Blood Pressure
Dogs
Female
Heart Rate
Hypophysectomy
Immunohistochemistry
Male
Oxytocin
Pituitary Gland, Posterior
Vasopressins
jenkins-FCD Prod-484 8aa07fc50b7f6d102f3dda2f4c7056ff84294d1d