Direct regulation by calcium of cytoplasmic messenger ribonucleic acid coding for pre-proparathyroid hormone in isolated bovine parathyroid cells.

DNA complementary to bovine preproparathyroid hormone mRNA was cloned and labeled by nick translation in order to measure mRNA by molecular hybridization. Bovine parathyroid cells were maintained in primary tissue culture for periods up to 96 h at 0.5 mM, 1.25 mM, and 2.5 mM calcium, which was followed by extraction of cellular RNA. Levels of mRNA showed no differences at 0.5 or 1.25 mM calcium, but at high calcium levels, there was a reversible decrease that began at 16 h to a plateau at 30% of control after 72 h. These studies suggest that the glandular capacity to synthesize hormone may be at or near maximal at normal calcium, but at high calcium, there is a decrease over time in steady state levels of mRNA.