Neuroendocrine effects of acute nickel chloride administration in rats

An sc injection of nickel chloride (20 and 10 mg/kg) led to a profound and consistent increase of circulating prolactin (PRL) levels after 1 day and lasted for 4 days ( p < 0.001) in male rats. Increases in insulin levels occurred 1 and 2 days postinjection. The nickel-induced PRL rise could be abolished by a simultaneous administration of 2-bromo-α-ergocryptine (CB 154). In vitro incubation of pituitaries from rats that received 20 mg/kg of nickel chloride 48 hr prior to sacrifice released more PRL into the culture medium, as well as contained more PRL in the final tissue than did the pituitaries from control animals. The hypothalamic extracts (HE) obtained from hypothalami of nickel-injected rats were tested also in vitro on normal rat pituitaries and the results showed that the HE from such rats released more PRL and therefore had less prolactin-inhibiting factor (PIF) than the HE obtained from control rats. The results whow that nickel chloride has effects on the endocrine system that (a) last considerably longer than previously reported, (b) are mediated through the neuroendocrine system, and (c) instead of specifically inhibiting PRL secretion from the pituitary promote high circulating PRL levels lasting from 1 to 4 days.