Final answer:
The most useful hypothetical drug for treating cholera-induced diarrhea would increase the GTPase activity of the ADP-ribosylated stimulatory G factor (Gs), reducing elevated cAMP levels in the intestinal epithelial cells and the resulting excessive electrolyte and water loss.
Step-by-step explanation:
The question seeks to identify the hypothetical drug effect that would be most useful in treating diarrhea caused by cholera. The cholera toxin, produced by Vibrio cholerae, causes an increase in the cyclic adenosine monophosphate (cAMP) levels in intestinal epithelial cells. This triggers the activation of a chloride channel that results in excessive electrolyte and water loss, characteristic of cholera-induced diarrhea. In order to mitigate the symptoms of cholera, an appropriate drug would need to counteract the effects of the increased cAMP levels.
Therefore, the correct answer would be E. increases the GTPase activity of the ADP-ribosylated stimulatory G factor (Gs). By increasing the GTPase activity, the drug would effectively reduce the active duration of the Gs protein, thereby reducing the overproduction of cAMP caused by the toxin and consequently stalling excessive fluid and electrolyte secretion into the intestinal lumen. This would help in the treatment of cholera by reducing the severity of the diarrhea.