The role of endorphins and vasopressin in canine endotoxin shock.

Chemical antagonists were used to assess the role of beta-endorphin and arginine-vasopressin (AVP) in canine endotoxin shock. Fifteen awake dogs were given Escherichia coli endotoxin IV. Within 5 min, CO decreased to 28%, LV dP/dt to 46%, and MAP to 52% baseline. Fifteen minutes after endotoxin, five dogs each received naloxone, AVP antagonist, or no treatment. Control (untreated) animals exhibited persistent cardiovascular depression, with CO 49%, LV dP/dt 69%, and MAP 91% of baseline after 45 min. Naloxone improved CO to 69%, LV dP/dt to 94%, and MAP to 91% by 30 min after treatment. AVP blockade improved CO to 105%, LV dP/dt to 107%, and MAP to 95% of baseline by 30 min after treatment, and caused significant tachycardia. Plasma cortisol and AVP increased markedly in all groups after endotoxin administration. AVP antagonist treatment increased mean survival from 1.4 to 4 days. These data suggest that abnormally elevated AVP contributes to cardiovascular depression in canine endotoxin shock and that AVP blockade is therapeutic in the animal model studied.