Abstract
1. The release of oxytocin from the isolated pituitary glands of the rat were determined by the bio-assay, measuring the milk-ejection pressure.
2. Ca++ is required for the high release of oxytocin observed when the glands are stimulated by exposing to excess K Locke's solution.
3. The release of oxytocin is potentiated in Na-deficient media.
4. Tetrodotoxin (5×10-7g/ml) can suppress the release of oxytocin, and this suppressive effect is also seen in Na-deficient media.
5. The addition of Mg++ (8.8mM) in the media fairly well suppresses the release of oxytocin.
6. Ba++ can substitute Ca++ for the release of oxytocin.
7. The similarity between the release mechanisms of oxytocin and vasopressin and the necessity of Ca++ in the stimulus-secretion coupling were discussed.
