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The effect of various concentrations of cadmium (Cd) in levels ranging from 0.75 to 12 μg/ml medium, on the secretion of human chorionic gonadotropin (hCG) in first-trimester placental expiants, after 6 or 24 h incubation, employing both static and dynamic systems was examined. Later the unbound Cd was washed for 45 min with fresh medium devoid of Cd, followed by superfusion with the latter medium for 75 min, during which time samples were collected for hCG assay. For the superfusion experiments the parameters used for evaluating the hCG secretion pattern were: mean peak amplitude (MPA), pulse frequency (PF) and the area under the hCG secretion curve (AUC). The results indicate that in the dynamic system the hCG secretion increased significantly, and this increase was dose dependent. There was also a dose-related increase in mean total hCG secreted by the explants exposed to Cd. Maximal hCG secretion was observed after 24 h exposure of explants to 6 μg of the metal/ml. Both the MPA and AUC parameters showed a statistically significant increase for this dose level. At 12 μg/ml, the pulsatile secretion of hCG decreased, the value for the mean hCG secretion being comparable to that observed for 0.75 μg/ml. After 6 h incubation, however, there were no significant changes from the control, as judged by all of the above parameters. The levels of hCG secreted by the explants into the media in the static system were not significantly different from their respective controls, for both incubation periods and Cd levels. These results indicate that Cd may affect the normal placental function, as reflected in its hCG secretion pattern. [ABSTRACT FROM AUTHOR]