Quantitative parathyroid morphology is unaltered in prolonged hypocalcemia. A quantitative electron microscopic study in the Mongolian gerbil.

Hypocalcemia was induced in adult Mongolian gerbils by a combination of a calcium deficient diet and repeated injections of ethylene-diamine-tetra-acetate (EDTA). This treatment caused tetany and death in some of the animals. Laboratory analyses on the eight experimental day disclosed significantly decreased concentrations of serum calcium and significantly increased concentrations of serum phosphate. Stereological methods and semi-automatic image analysis were used for ultrastructural study of the parathyroid glands with the aim of disclosing if any quantitative alterations occur in prolonged hypocalcemia. Compared with normocalcemic animals no significant change was observed in the hypocalcemic gerbils with regard to the nuclear profile area, the volume densities of nucleus, mitochondria, endoplasmic reticulum, Golgi complex, lysosomes, secretory granules and storage granules, or the surface density of the cell membrane. The only significant change in the hypocalcemic animals was a slight increase in the volume density of lipoid bodies and a similarly slight decrease in the surface density of the endoplasmic reticulum, changes which at present are difficult to explain. The data demonstrate that hypocalcemic stimulation in vivo does not give rise to quantitative morphological changes in parathyroid chief cells, and thus do not support the idea of a functional adaptation of the chief cells to variations in the ambient calcium concentration.