Modulation of episodic adrenocorticotropin hormone secretion by cadmium in male rats

The effects of cadmium on adrenocorticotropin hormone(ACTH) secretion are controversial and seem todepend on the dose and duration ofthe exposure to the metal. This work was undertaken to analyze theeffects of acutecadmium administration on the episodic pattern of ACTH release in adult male rats. Forthispurpose, animals were cannulated 40 h before the experiment to allow a continuousblood withdrawal.Two and a half hours after the administration of a single dose ofcadmium chloride (4.5 mg kg bodyweight),the episodic pattern of ACTH wasanalyzed during three hours (from 10:30 to 13:30, samples beingcollectedevery seven minutes) in conscious and freely moving adult male rats. The mean valuesof ACTH duringthe bleeding period and the absolute pulse amplitude were decreased byacute cadmium chloride adminis-tration(P < 0.001, P < 0.01, respectively). Bycontrast, the frequency of ACTH pulses increased (P < 0.01).However, no changes inany other parameters of episodic ACTH secretion were observed compared withcontrolanimals. These data suggest that cadmium interferes with the regulatorymechanism of ACTH.