Prolactin response to dopamine and valproate administration in breast cancer patients.

There is only indirect evidence available at present to suggest the role of prolactin (PRL) in either the promotion or progression of human breast cancer. In order to determine if dopaminergic and GABAergic regulation of PRL are similar in breast cancer patients, we studied 2 groups of premenopausal women with no evident endocrine alteration: 1) control subjects (C); and 2) breast cancer patients (CA). Basal PRL levels were measured and their response to dopamine (DA) infusion (0.004 micrograms/kg/min) and valproate administration (400 mg/p.o.). The mean of percentage inhibition by DA in C (n = 6) was significantly higher than in CA (n = 11) at 180 min; P less than 0.025. On the other hand, group C (n = 8) responded to valproate with maximal inhibition at 180 min; in the CA group (n = 8) no inhibition was observed; P less than 0.0025.