The influence of calmodulin antagonists on calcium transport and uptake in the rat intestine.

The effects of calmodulin (CaM) antagonists on calcium transport, tissue retention and the cell-associated calcium space were determined in duodenal segments of intestine and isolated duodenal enterocytes from young male rats. The CaM antagonists trifluoperazine (TFP) and chlorpromazine (CPZ) which were added separately to the media bathing both the mucosal and serosal surfaces of duodenal segments decreased calcium transport and tissue uptake in a dose-related fashion over a concentration range of 0.1-1 mM. Both TFP and CPZ reduced active transport to a greater extent than calcium retention in the duodenal segments. In addition, TFP and CPZ produced a dose-related decrease in the observed intracellular calcium space in duodenal tissue and reduced calcium uptake into isolated enterocytes. The TFP-induced antagonism of calcium transport was greater when TFP was at the mucosal surface than at the serosal surface of the intestinal tissue. Although TFP and CPZ are not entirely specific CaM antagonists at the concentrations used in this study, the results indicate that CaM antagonism by TFP and CPZ decreases active calcium transport and calcium uptake in duodenal segments of rat intestine in a dose-related fashion. Therefore, the present study together with the reports of other investigators suggests that CaM is involved in the mediation of calcium translocation in intestinal tissue in a fashion which is similar to that reported in other biological tissue.