ACTION OF PROSTAGLANDIN-E2 ON THE SMOOTH-MUSCLE CELL OF THE GUINEA-PIG TAENIA-COLI

The effect of prostaglandin E2 (PGE2) on the smooth muscle cell of guinea pig taenia coli was investigated by measuring changes in membrane potential, membrane resistance, muscle contraction and ion fluxes. The action of PGE2 caused depolarization of the cell membrane, and increased spike activity and muscle contraction. The amplitude of the PGE2 depolarization was concentration-dependent. The action of PGE2 could be mimicked by depolarizing the muscle membrane with an external current with as result a decrease in membrane resistance similar to that observed in the presence of PGE2. The PGE2 depolarization was not abolished when the sodium pump was inhibited by omitting external potassium or in the presence of K-strophantin, persisted in low chloride Krebs and in low sodium solution, but was reduced in calcium-free solution and in the presence of D600. 45Ca influx was enhanced by PGE2, but 45Ca efflux was not affected. The 42K efflux was increased in the presence of PGE2, but this response was blocked by Ca-free solution. These results indicate that calcium permeability is enhanced by PGE2, and that this enhancement is associated with a depolarization of the muscle cell membrane of the guinea-pig taenia coli. © 1979.