Actions of prostaglandins and indomethacin on the electrical and mechanical properties of smooth muscle cells of the guinea-pig ileocecal junction.

The effects of prostaglandins (PGs) and indomethacin on the mechanical and membrane properties of the smooth muscle cells of the guinea-pig ileocecal junction were studied using microelectrode and tension recording techniques and radioimmunoassay to determine levels of PGs. In the guinea-pig ileocecal junction, we found two distinct cell populations-cells with, and without spontaneous electrical and mechanical activities. PGs (PGE1, PGE2, PGF2 alpha) in low concentrations suppressed spontaneous mechanical activity. Correspondingly, PGs (greater than 10-7 M) suppressed both spontaneously generated spikes and evoked spikes, presumably due to an increase in the threshold for generation of action potential. On the contrary, indomethacin evoked rhythmic spontaneous contractions in the mechanically quiescent muscle preparations and reduced the PGE and PGF content of the muscle. Spontaneous spike discharges occurred during the indomethacin-induced contractions. The spontaneous electrical and mechanical activities induced by indomethacin were suppressed by PGs, in low concentrations. These results indicate that under physiological conditions, the endogenous PGs in the muscle may play an important role in regulation muscle tone as well as the membrane properties, thereby contributing to the regulation of motility of the intestine and possibly the sphincter.