Protein Kinase C Mediates the Calcium-Induced Activation of Rat Colonic Particulate Guanylate Cyclase

The present studies were conducted to determine whether [3H]quinuclidinyl benzilate binding in rat colonic membranes and/or carbachol-mediated stimulation of particulate guanylate cyclase were altered by changes in vitamin D status. EC50 values for the stimulation of colonic guanylate cyclase by carbachol were found to be significantly greater in vitamin D-deficient rats compared to their D-sufficient counterparts. Concomitantly, the density of receptors ( B max) were significantly lower, and dissociation constants ( K d) were significantly higher in D-deficient colonic membranes. In vitamin D-repleted animals, moreover, all of these aforementioned alterations were at least partially corrected.