Which receptor types are directly impacted by cholera toxin to result in secretory diarrhea?

Cholera toxin primarily affects Gs receptors, which are a type of G-protein coupled receptor that stimulates adenylate cyclase. When cholera toxin enters intestinal epithelial cells, it catalyzes the ADP-ribosylation of the Gs alpha subunit. This modification locks the Gs protein in its active form, leading to prolonged stimulation of adenylate cyclase and an increase in intracellular cyclic AMP (cAMP) levels.

The elevated cAMP levels in turn stimulate the secretion of chloride ions into the intestinal lumen, followed by sodium and water, resulting in the characteristic secretory diarrhea associated with cholera infection. The increase in cAMP disrupts the normal absorption processes and pushes fluid into the intestinal lumen, overwhelming the capacity of the intestinal tract to absorb it, culminating in diarrhea.

Understanding the mechanism of Gs receptor activation by cholera toxin is crucial for recognizing how this bacterial toxin leads to electrolyte imbalances and significant dehydration due to excessive fluid loss.