Dexamethasone and calcium interact in the regulation of parathormone and chromogranin-A secretion and messenger ribonucleic acid levels in parathyroid cells

We investigated the interaction of dexamethasone and Ca2+ on the secretion of PTH and chromogranin-A (CgA) by porcine parathyroid cells in culture and on the cellular levels of PTH and CgA mRNA. Freshly dispersed parathyroid cells were cultured for 6 days in Ham's F-12 medium containing 10% fetal calf serum and 1 mM Ca2+. The experiments were initiated at 0.5 or 3.0 mM Ca2+ in 0.5% serum with or without dexamethasone for an additional 24 or 48 h. Secretion of PTH and CgA was 50-60% less, and the respective mRNAs levels were about 75% lower at 3.0 than at 0.5 mM Ca2+. Dexamethasone (10(-9)-10(-7) M) stimulated the secretion of PTH in a dose-dependent fashion about 2-fold at both 3.0 and 0.5 mM Ca2+ and increased the PTH mRNA level 15-fold at the high and 3-fold at the low Ca2+ concentration. In contrast, the direction of action of dexamethasone on the secretion of CgA and CgA mRNA was dependent upon the Ca2+ concentration. At 3.0 mM Ca2+, dexamethasone increased CgA secretion and mRNA levels about 2- and 8...