POSITIVE INOTROPIC ACTIVITY OF CHOLERA ENTEROTOXIN ON EMBRYONIC CHICK HEART

  • 1 January 1976
    • journal article
    • research article
    • Vol. 197  (1) , 27-37
Abstract
The characteristics of the positive inotropic effect of different preparations of cholera toxin on the isolated 4 day old embryonic chick heart were investigated. Crude (CCT) and partially purified and purified (PCT) preparations of cholera toxin had positive inotropic activity. Contractility was increased within 1 min and reached a maximum at .apprx. 40 min after exposure to toxin. Activities of all 3 toxin preparations were abolished by heating; their effects were prevented by addition of antitoxin, but not propranolol, before exposure of the heart to toxin. The positive inotropic effect of PCT was not reversed by washing, but was reversed by subsequent addition of antitoxin. The effects of CCT were reversed by insulin. Effects of CCT and PCT were potentiated by theophylline, and both toxins elevated tissue levels of cyclic AMP. A filtrate of CCT (MW < 30,000) exhibited similar cardiostimulant activity but displayed certain differences from the other toxin preparations. The filtrate was heat stable, and its effects were blocked by pretreatment with propranolol but not by antitoxin. The filtrate of CCT, unlike the toxin-containing preparations, did not stimulate intestinal fluid secretion in the dog.

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