Stimulation of intestinal adenyl cyclase by Escherichia coli enterotoxin: comparison of strains from an infant and an adult with diarrhea.

Abstract

The effects of Escherichia coli enterotoxin on the activity of adenyl cyclase in intestinal mucosa were determined in the small intestine of the rabbit. In vivo incubation of enterotoxin in isolated intestinal loops for 2–4 hr led to an increase in the activity of adenyl cyclase in mucosal epithelial cells. The degree of stimulation of the enzyme was proportional to the concentration of enterotoxin. The levels of activity were additive when enterotoxin-treated, homogenized mucosal cells were exposed to prostaglandin E1. The activity of adenyl cyclase in both enterotoxin-treated and control preparations was stimulated markedly by NaF. Phosphodiesterase activity was not altered in enterotoxin-treated loops. Enterotoxin was partially inactivated when held at 60 C for 15 min; it was completely inactivated at 100 C. Differences in the degree of stimulation of adenyl cyclase were noted among strains of E. coli. Enterotoxin from a strain isolated in an adult in Calcutta with choleralike symptoms was a more potent stimulator of adenyl cyclase than enterotoxin from a strain of E. coli associated with a mild case of diarrhea in an infant in Chicago.