Effect of cholera toxin on cAMP levels and Na+ influx in isolated intestinal epithelial cells.
Freshly isolated chicken intestinal cells contain approximately 20 pmol adenosine 3',5'-cyclic monophosphate (cAMP)/mg cellular protein. Incubation with 3 micrograms/ml cholera toxin (CT) at 37 degrees C induces an elevation of cellular cAMP beginning 10-15 min after initial exposure. The response is linear with time for 40-50 min and causes a six- to eightfold increase over control levels at steady state. Dibutyryl cAMP and agents that increase cAMP production inhibit Na+ influx into the isolated enterocytes. Chlorpromazine completely abolishes the toxin-induced elevation of cAMP in the isolated cells and also reverses the effect on Na+ entry. The data provide evidence for a cAMP-mediated control of intestinal cell Na+ uptake, which may represent the mechanistic basis for the antiabsorptive effect of CT on Na+ during induction of intestinal secretory activity. Studies on the time-dependent effects of chlorpromazine on both intracellular cAMP concentration and Na+ influx suggest that the reactivation of the Na+ transport system after cAMP-induced inhibition is slow relative to the disappearance of cAMP.
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002116:Calcitonin / Q000494:pharmacology; D002645:Chickens; D002746:Chlorpromazine / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology; D013997:Time Factors
D003994:Bucladesine; D002116:Calcitonin; D002772:Cholera Toxin; D012964:Sodium; D013806:Theophylline; D000242:Cyclic AMP; D002746:Chlorpromazine