Cadmium does not inhibit pulsatile prolactin secretion through TRH

This work was undertaken to analyse the effects of acutecadmium administration on the pulsatile patternof prolactin release, in adult male rats.For this purpose, animals were cannulated 40 h before the experi-mentto allow a continuousblood withdrawal. Two hours after the administration of one dose of cadmiumchloride (4.5 mg kg1 ), the pulsatile pattern of prolactin, during three hours, was studied. The effects oftwopulses of thyrotropin-releasing hormone (TRH) (1 mg per rat), given 60 and 120 min afterstarting the periodof blood sampling, were studied. The mean values of prolactin during thebleeding period and the absolutepulse amplitude were decreased by acute cadmium chlorideadministration. However, no changes in anyother parameters of prolactin pulsatility were observed.TRH administration to control rats increased meanprolactin levels, and absolute andrelative pulse amplitudes, but decreased the mean half-life of the hormone.In animals pretreated withcadmium, TRH increased the mean levels of prolatin, and absolute and relativeamplitudes ofthe hormone pulses. No other parameter studied was changed by TRH in cadmiumpretreatedrats. These data suggest that acute administration of cadmium did not inhibit thepulsatile prolactin releasethrough TRH.