Effects of Ca2+ and calmodulin antagonists on the Na+ pump activity induced by pilocarpine in dog submandibular gland.

The effects of Ca2+ and calmodulin antagonists on the Na+,K+-ATPase activity were investigated in dog submandibular gland pieces. The Na+,K+-ATPase activity of the gland pieces which were incubated in the presence of 5 microM A23187, a Ca2+ ionophore, was about 2-fold of that seen in the control medium. Verapamil, diltiazem and La3+ (Ca2+ antagonists) and chlorpromazine, trifluoperazine and W-7 (calmodulin antagonists) had no significant effect on the Na+,K+-ATPase activity in the control medium, but significantly inhibited that induced by pilocarpine. These results suggest that the Na+ pump activity is modified by the Ca2+ influx from the extracellular spaces and the intracellular Ca2+-calmodulin complex.