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Abstract

This work was undertaken to analyse the effects of acute cadmium administration on the pulsatile pattern of prolactin release, in adult male rats. For this purpose, animals were cannulated 40 h before the experiment to allow a continuous blood withdrawal. Two hours after the administration of one dose of cadmium chloride (4.5 mg kg1), the pulsatile pattern of prolactin, during three hours, was studied. The effects of two pulses of thyrotropin-releasing hormone (TRH) (1 microgram per rat), given 60 and 120 min after starting the period of blood sampling, were studied. The mean values of prolactin during the bleeding period and the absolute pulse amplitude were decreased by acute cadmium chloride administration. However, no changes in any other parameters of prolactin pulsatility were observed. TRH administration to control rats increased mean prolactin levels, and absolute and relative pulse amplitudes, but decreased the mean half-life of the hormone. In animals pretreated with cadmium, TRH increased the mean levels of prolactin, and absolute and relative amplitudes of the hormone pulses. No other parameter studied was changed by TRH in cadmium pretreated rats. These data suggest that acute administration of cadmium did not inhibit the pulsatile prolactin release through TRH.

Cadmium effects on dopamine turnover and plasma levels of prolactin, GH and ACTH

“…Cadmium effectively depressed prolactin in both in vivo and in vitro studies (14,15,22). Such inhibitory effect could be explained by the decreased amplitude of prolactin peaks reported elsewhere (13). Cadmium may act directly on the lactotrophs, through an interaction with the prolactin molecule, that is sensitive to divalent metals, as was shown in vitro (22).…”

“…Cadmium may act directly on the lactotrophs, through an interaction with the prolactin molecule, that is sensitive to divalent metals, as was shown in vitro (22). However, previous studies in vivo indicated a normal response of prolactin to the thyrotropin releasing hormone (TRH) in cadmium-treated rats (13), thus indicating a differential intracellular kinetics of cadmium in vivo as compared to the in vitro studies using cultures of pituitary cells (22). The effects of the metal on D A at the median eminence would be suggestive of increased rather than decreased plasma prolactin levels, considering the well known inhbitory role of DA on prolactin (9).…”

“…Plasma levels of prolactin, GH and ACTH were determined by specific double-antibody radioimmunoassay (12)(13)(14)(15)(16)(17)(18)(19). …”

“…Cadmium was given at a concentration of 50 ppm of cadmium chloride (CdCh) in the drinking water (calculated daily dose per rat: 2 mg/Kg body weight). The dose was selected according to previous works from literature (13,25). This dose modified the pulsatile LH and prolactin secretion in male rats (15,16).…”