Effect of potassium on PTH secretion from dispersed bovine parathyroid cells

The effects of potassium on PTH secretion were studied in dispersed bovine parathyroid cells. Removal of extracellular potassium markedly inhibited low calcium-stimulated PTH release. This inhibition was dose-dependent, with a half-maximal effect at 1-2 mM. Above 2-3 mM potassium, there was relatively little further increase in maximal secretory rate, but there was a progressive increase in the "set-point" for calcium-regulated PTH release, analogous to that which we have observed previously with lithium. These changes in secretory function were not associated with any change in cellular cAMP. Low extracellular potassium, however, caused a striking reduction in the ratio of intracellular potassium to sodium, while a reciprocal change was brought about by high extracellular potassium. These studies suggest that alterations in secretory function induced by changes in extracellular potassium, which are phenomenologically similar to those found in states of pathologic parathyroid function in man, may be related to changes in intracellular monovalent cations.