The 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.