Which of the following stimulate adenylate cyclase with G-protein coupled action -

Ans. is 'b' i.e., Cholera toxin Cholera toxino V. cholerae produces cholera toxin, the model for enterotoxins, whose action on the mucosal epithelium is responsible for the characteristic diarrhoea of the cholera.o Cholera toxin is a protein complex made up of six subunits - a single copy of 'A' subunit (Port A) and five copies of'B' subunit (Part B). 'A' subunit has two fragments; A1 and A2.o cAMP inhibits the absorptive sodium transport system (decreases sodium & chloride reabsorption) and activates the secretory chloride transport system (increases chloride and bicarbonate secretion)o This leads to accumulation of sodium choride in the intestinal lumen.o Accumulated sodium chloride draws water into the lumen due to increased osmolality leading to watery> diarrhoea.