Effects of saline infusions on calcium concentration in plasma ultrafiltrate and on the ultrastructure of the parathyroid glands of the rat

Summary Experiments have been performed in adult female rats to examine the effects of saline infusion on calcium concentration in plasma ultrafiltrate and on the ultrastructure of the parathyroids as studied with the electron microscope. Intravenous infusions of isotonic saline of at least 10 ml within 30 min decreased calcium concentration in plasma ultrafiltrate from 3.04±0.15 mEq/l to 2.79±0.11 eEq/l (P<0.001). Saline infusions of 2 h duration at a rate of 0.5 ml/min decreased significantly the number of secretory granules in the parathyroid cells and induced considerable growth of the Golgi apparatus. It is concluded, that saline infusions in the rat decrease the ionized fraction of plasma calcium concentration thereby increasing parathormone secretion rate.This work was supported in part by a grant from the Deutsche Forschungsgemeinschaft.