Modulation of episodic adrenocorticotropin hormone secretion by cadmium inmale rats

The effects of cadmium on adrenocorticotropin hormone (ACTH) secretion are controversial and seem to depend on the dose and duration of the exposure t o the metal. This work was undertaken to analyze the effects of acute cadmi um administration on the episodic pattern of ACTH release in adult male rat s. For this purpose, animals were cannulated 40 h before the experiment to allow a continuous blood withdrawal. Two and a half hours after the adminis tration of a single dose of cadmium chloride (4.5 mg kg(-1) bodyweight), th e episodic pattern of ACTH was analyzed during three hours (Com 10:30 to 13 :30, samples being collected every seven minutes) in conscious and freely m oving adult male rats, The mean values of ACTH during the bleeding period a nd the absolute pulse amplitude were decreased by acute cadmium chloride ad ministration (P less than or equal to 0.001, P less than or equal to 0.01, respectively). By contrast, the frequency of ACTH pulses increased (P less than or equal to 0.01), However, no changes in any other parameters of epis odic ACTH secretion were observed compared with control animals, These data suggest that cadmium interferes with the regulatory mechanism of ACTH.