The S-S Polypeptide Receptor as a Metal Receptor
It has long been known that the magnesium content of Ringer solution affects the activity of S-S polypeptides (Fraser, 1939; Stewart, 1949). Thus, when the activity ratio of oxytocin/vasopressin is measured in the isolated uterus in the absence and presence of magnesium, it is found that the activity ratio changes in favour of vasopressin in solutions which contain magnesium although vasopressin remains less active than oxytocin on a molar basis. It seems probable that this effect is due to a selective potentiation of vasopressin by magnesium. Magnesium, although it improves the activity of several synthetic S-S polypeptides relative to oxytocin, has no effect on the activity of desaminooxytocin, one synthetic polypeptide which is definitely more active than oxytocin (Munsick, 1968.)
KeywordsElectron Donor Group Potentiating Effect Contractile Effect Potassium Sulphate Cupric Sulphate
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