Enhancement of the stimulatory effect of calcium on aldosterone secretion by parathyroid hormone.

In previous clinical investigations on uremic patients we found a stimulatory effect of the presence of hyperparathyroidism on the Ca(2+)-induced secretion of various hormones, i.e. aldosterone and vasopressin. The present investigation, therefore, examined the possible effect of PTH on the calcium-mediated aldosterone secretion from isolated, purified zona glomerulosa cells obtained from the rat. After washing the cells and after 30 min of preincubation Ca2+ was added to the preparations at concentrations from 0.5 to 2.0 mmol and PTH(1-84) or PTH(1-34) were added at concentrations from 10(-7) to 10(-10) M. The cells were then incubated for 120 min and aldosterone measured in the supernatant. The aldosterone response to Ca2+ stimulation--without PTH added--served as baseline controls, while cell preparations with ACTH 10(-6) M added secured the viability and responsiveness of the cells. In all cell preparations with PTH(1-84) as well as PTH(1-34) added the aldosterone responses to a certain Ca2+ concentration increased significantly by up to 200% (p < 0.001) above baseline values. It is suggested that PTH may have a Ca2+ ionophore-like effect on endocrine glands, which are not normally related to PTH and thus enhance the calcium-stimulated hormone secretion. The hypothesis is raised that this phenomenon may take place in uremia during the state of secondary hyperparathyroidism.