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In vitro and in vivo cadmium toxicity studies focus almost exclusively on CdCl2 effects. Only a few studies have used adrenocortical cells and tissue to determine cadmium salt effects during stress of adrenocorticotropin stimulation. Because several biologically relevant water-soluble cadmium salts exist, this study extended work with CdCl2 to evaluate the acute adrenocortical cell steroid secretory responses to non-lethal cadmium acetate (CdAc2) and CdSO4 concentrations. Control or ACTH-stimulated cultured Y-1 mouse adrenal tumor cells (ATCC) which secrete 20alpha-dihydroprogesterone (20-DHP) were incubated for 0.5 h in serum-free medium (FMEM) with or without 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0 and 1000.0 microg CdAc2 or CdSO4/ml FMEM (1.9, 3.8, 19.0, 38.0, 190.0, 380.0 and 1900.0 micromol/L, respectively). For each salt, cell viability was measured at the end of the incubation using live cell trypan blue exclusion. In addition, cumulative CdAc2 effects during 4 h incubations and effect reversibility were determined for control and stimulated cells. After each experimental incubation, the 20-DHP secreted into the medium was determined by radioimmunoassay. Over 80% of all control or ACTH-stimulated cells were viable after incubation in the presence or absence of various CdAc2 or CdSO4 concentrations. Cadmium acetate and sulfate inhibited basal and ACTH-stimulated steroid secretion in a dose-dependent manner. For basal steroid secretion the CdAc2 concentration that first significantly inhibited was 0.5 microg/ml medium (1.9 micromol/L); stimulated secretion was significantly inhibited beginning at 5.0 microg/ml (19.0 micromol/L) and the concentration reducing stimulated 20-DHP secretion by 50% (IC50) was 5.6 microg/ml (21.3 micromol/L). Similarly, the first CdSO4 concentration to significantly inhibit basal and ACTH-stimulated steroid secretion was 10.0 microg/ml medium (39.0 micromol/L); the IC50 was 7.8 microg/ml (29.8 micromol/L). Except that basally secreting Cd2+-treated cells almost doubled 20-DHP secretion after Cd2+ removal and subsequent incubation with ACTH, all basal and ACTH-stimulated steroid secretion was irreversibly inhibited by every CdAc2 concentration. All CdAc2 concentrations initiated and maintained cumulative inhibitory effects on basal and ACTH-stimulated steroid secretion over a 4 h period. Reversibility and cumulative CdSO4 treatment studies were not conducted. Based on the results from the present studies, both CdAc2 and CdSO4 appeared to incrementally inhibit control and ACTH-stimulated steroidogenesis without affecting cell viability and to be more potent inhibitors of adrenocortical cell steroid secretion than CdCl2. Finally, CdAc2 effects on control and stimulated cells were cumulative and irreversible. |
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