CALCIUM MODULATES THE SYNTHESIS OF PROSTAGLANDIN E(2) IN ISOLATED COLONIC MUCOSAL CELLS

Background/Aims: The effect of calcium on. colonic prostaglandin E(2) synthesis was investigated in 26 healthy volunteers. Material and Meth ods: Biopsy specimens were obtained by colonoscopy and the mucosal cel ls were separated biochemically. The cells were incubated in EDTA or C aCl2 containing media for 15 and 30 minutes. Results: The PGE(2) synth esis was significantly (p < 0.001) diminished in the calcium free susp ension (EDTA) compared to the CaCl2 containing suspension. To increase intracellular Ca2+ concentration, calcium ionophore A 23187 was added for the last 15 minutes. It significantly stimulated the prostaglandi n production. In addition, the calcium channel blocker verapamil did n ot alter the PGE(2) synthesis, whereas trifluoperazine, a calmodulin i nhibitor, markedly decreased the production rate. Conclusion: Calcium is an important stimulus of prostaglandin synthesis and inhibition of calmodulin by trifluoperazine decreases the arachidonic metabolism. In these regards, colonic tissue shares features with other tissues. How ever, in contrast to smooth or cardiac muscle, intracellular calcium c oncentration in colonic mucosa is not affected by verapamil, indicatin g that colonic calcium channels have a different affinity to this drug .