MODULATION OF ADRENAL-CELL FUNCTIONS BY CADMIUM SALTS .1. CADMIUM CHLORIDE EFFECTS ON BASAL AND ACTH-STIMULATED STEROIDOGENESIS

Cultured Y-1 mouse adrenal tumor cells, which secrete 20-alpha-hydroxy -4-pregnen-3-one (20-DHP) were used to investigate the acute nonlethal effects of incremental cadmium chloride (CdCl2) concentrations on bas al and maximally stimulated steroid secretion. In addition, cumulative CdCl2 effects during 4-hr incubations, effect reversibility, and viab ility were determined. Cells were incubated in 1 ml serum-free Eagle's Minimal Essential Medium (FMEM) with or without 0.5 IU (ca. 1.5 mu M) adrenocorticotropin (ACTH) in the presence or absence of CdCl2. Follo wing incubation, cell viability was quantitated using trypan blue excl usion. The 20-DHP secreted into the experimental incubation medium was measured by radioimmunoassay. CdCl2 levels of 10.0 mu g/ml or greater significantly inhibited basal 30 min steroid secretion in a dose-depe ndent manner; ACTH-stimulated steroid secretion was significantly inhi bited by levels 5.0 mu g/ml or greater. At least 80% of all control an d stimulated cells in the presence or absence of cadmium ions excluded trypan blue. The reduction in ACTH-stimulated steroid secretion was g reater than the reduction in basal steroid secretion at any cadmium co ncentration level. The CdCl2 concentration that reduced stimulated ste roid hormone secretion by 50% (IC50) was 45.0 mu g/ml. Exposing Y-1 ce lls to either 5.0, 10.0, 45.0 or 500.0 mu g CdCl2/ml FMEM for periods ranging from 0.5 to 4 hr inhibited ACTH-stimulated steroid secretion i n a time-dependent manner. After 30 min exposure to 10.0, 45.0 or 500. 0 mu g CdCl2/ml FMEM with or without ACTH, cadmium inhibition was irre versible. When 5.0 mu g CdCl2/ml was used, basal and stimulated inhibi tion was reversible by reincubating in medium containing ACTH alone. T he relatively greater cadmium effects on ACTH stimulated steroidogenes is might suggest that cadmium modulated the rate-limited transducing s ystem between the ACTH plasma membrane receptor complex and cholestero l side-chain cleaving mitochondrial enzymes. However, cadmium influenc es on basal secretion indicated effects on the non-rate-limited steroi dogenic pathway.