The depletion of plasma prolactin by pantethine in oestrogen-primed hyperprolactinaemic rats.

Pantethine was investigated for its potential to deplete prolactin in the plasma and pituitary cells of oestrogen-primed hyperprolactinaemic rats. This compound has been used in the past to deliver cysteamine systemically, through its congener pantetheine, a metabolic precursor for cysteamine. Cysteamine itself, specifically reduces plasma and pituitary prolactin. The addition of pantethine (2-10 mmol/l) to the media of isolated pituitary cells over 4 h did not appreciably alter the intracellular content of immunoreactive prolactin. Moreover, oral administration of pantethine at 0.5 and 1.0 g/kg body weight did not influence the concentration of immunoreactive plasma prolactin. However, the concentration of plasma prolactin fell by 48 and 67%, when pantethine was injected i.p. at 0.5 and 1.0 g/kg body weight, after 4 h. Intravenous administration of pantethine resulted in even greater losses of prolactin, in the order of 50 and 81% depletion for 0.5 and 1.0 g/kg body weight respectively and within 2 h of administration. However, cysteamine was found to be more efficacious than pantethine on a molar basis with regard to depleting the plasma concentration of prolactin in hyperprolactinaemic rats.