The Action of the Prostaglandins on Isolated Human Ureteric Smooth Muscle

Abstract

Summary— A study has been carried out on the actions of the prostaglandins E₂ and F_2α and their synthesis inhibitors, indomethacin and diclofenac sodium, upon isolated human ureteric smooth muscle, using the technique of microsuperfusion designed to ensure good tissue viability. Indomethacin and diclofenac sodium were shown to abolish almost completely the contractile response of ureteric muscle to electrical field stimulation. Contractile activity, in the presence of the inhibitors, could be restored by prostaglandin E₂ or F_2α or by increasing the external potassium concentration, [K⁺]_o, of the superfusate. Prostaglandin E₂ or F_2α alone were shown to increase dramatically both the phasic and tonic component of the electrically stimulated contractions, on occasions inducing spontaneous activity. A possible mechanism of action was elucidated with an electrophysiological technique using intracellular microelectrodes. The mean membrane potential recorded was 54.7 mV (SD ± 10 mV, n=15). The depolarising action of raising [K⁺]_o was demonstrated and prostaglandin F_2α (3 times 10^-6M) was shown to produce a small depolarisation of the ureteric muscle cell membrane.