Saline infusion causes rapid increase in parathyroid hormone and intracellular calcium levels

Previous data demonstrate that increasing dietary NaCl causes an increase in intracellular calcium, possibly due to elevations in parathyroid hormone (PTH). To ascertain whether NaCl can induce a rise in PTH and thereby raise intracellular calcium, five adult males were infused with normal saline, and plasma was analyzed for intact PTH and erythrocytes for intracellular calcium at 15-minute intervals. Saline infusion caused a significant increase in PTH within 15 minutes and in intracellular calcium within 30 minutes. To further demonstrate that PTH was directly responsible for the increased intracellular calcium, erythrocyte suspensions were incubated with PTH, and the PTH caused significant, sustained elevations in erythrocyte total intracellular calcium. These data indicate that NaCl-induced increases in vascular resistance may result, in part, from PTH-induced increases in intracellular calcium.