Effects of cholera and E. coli enterotoxins on cyclic adenosine 3',5'-monophosphate levels and intermediary metabolism in the thyroid.

Abstract

The effects of cholera enterotoxin on dog thyroid cyclic adenosine 3',5'–monophosphate (cyclic AMP) levels and intermediary metabolism were studied and compared to those of thyrotropin (TSH) and E. coli enterotoxin. Although TSH stimulates cyclic AMP and 14CO2 formation within minutes, both crude and purified cholera enterotoxin (choleragen) required 25 min to stimulate cyclic AMP and 45 min to increase l–14C—glucose oxidation. E. coli enterotoxin stimulated 14CO2 formation during a 45–min incubation without producing any change in cyclic AMP. However, E. coli enterotoxin did increase cyclic AMP levels during a two—hr incubation. Choleragen and cholera enterotoxin increased adenylate cyclase activity in homogenates prepared from thyroid slices which had been previously incubated with the enterotoxins. Unlike TSH, they had no effect when added directly to the homogenate. The effect of choleragen on cyclic AMP formation occurred in the absence of, but was potentiated by, 10-2M theophylline. Despite the dela...