The Requirement of Cortisol for the Inhibitory Effect of Norepinephrine on the Antidiuretic Action of Vasopressin ∗

Abstract

Summary

Cortisol (CpF) is required for various physiological actions of norepinephrine (NE). In humans and animals, NE abolishes the antidiuretic action of arginine vasopressin (AVP). This study evaluates whether CpF is necessary for the interaction between NE and AVP on the kidneys. Six trained adrenalectomized (ADX) dogs were maintained with desoxycorticosterone acetate DOCA and 8 g of NaCl/day but without CpF for 3 days prior to study which was carried out in the awake animal. In this state, the dogs were volume expanded with weight gain of 0.7 to 1 kg and moderate water diuresis could be induced. With intravenous infusion of AVP (15-25 mU/hr) urine volume (UV) fell from 2.66 ± 0.55 (SE) to 0.98 ± 0.23 ml/min and urinary osmolality (Uosm) rose from 248 ± 32 to 513 ± 42 mOsm/kg H₂O. Addition of NE (360-600 μg/hr) did not abolish the effect of AVP. Intravenous injection of CpF (50 mg) increased water diuresis in the control periods, and the infusion of AVP to CpF and DOCA-treated ADX dogs also produced a fall in UV from 4.48 ± .50 to .69 ± .11 ml/min and a rise in Uosm from 151 ± 34 to 663 ± 69 mOsm/kg H₂O. Addition of NE to these animals abolished the action of AVP with both UV and Uosm returning to control values, 4.68 ± 0.55 ml/min and 135 ± 27 mOsm/kg H₂O, respectively. The results show that the inhibitory effect of NE on AVP action on kidney requires CpF.