THE EFFECTS OF N-ETHYLMALEIMIDE AND GLUTATHIONE ON THE ISOLATED RAT UTERUS AND FROG BLADDER WITH SPECIAL REFERENCE TO THE ACTION OF OXYTOCIN

Abstract

SUMMARY 1. The effect of oxytocin on both the rat uterus and frog bladder is abolished by solutions of 1 mm N-ethylmaleimide (NEM). 2. NEM, however, has a variety of effects on these tissues. It inhibits sodium transport across the bladder, it prevents relaxation of the uterus and the return of water transfer to normal after it has been affected by oxytocin, and it inhibits contraction of the uterus by acetylcholine. 3. Reduced and oxidized glutathione (GSH and GSSG) inhibit the action of oxytocin on the uterus reversably and this inhibition is competitive. 4. GSH and GSSG also inhibited the increase in water transfer by oxytocin across the frog bladder, GSSG was more potent. Sodium transport across the bladder was transiently reduced by GSH and decreases by about 50% in the presence of GSSG. 5. The results are discussed in relation to the possible mechanism of interaction of neurohypophysial hormones with their receptors. It is concluded that both S-S and SH groups are present at the receptor sites in both the rat uterus and frog bladder.