Prostaglandin F2alpha (PGF2alpha)-induced contraction and calcium movement in longitudinal muscle of guinea-pig isolated stomach.

Calcium movement and contractile responses to high K+ concentration and PGF2alpha were investigated in guinea-pig stimach longitudinal muscle. High K+ concentration (30 mM) and PGF2alpha (10(-7) M) produced similar contractions of guinea-pig stomach longitudinal muscle. The 'Ca-antagonist', verapamil (10(-5)-10(-4) M), prevented high K-induced contraction, but did not greatly reduce contractions to PGF2alpha. 45Ca uptake was increased by high K(30 mM) or PGF2alpha(10(-7) M). These increases in 45Ca uptake were greatly reduced with 10(-4) M verapamil. The results suggest that high K-induced contraction may depend on an increase in Ca influx. PGF2alpha-induced contraction may depend on both an increase in Ca influx and on an intracellular release of Ca.