Morphometric analysis of parathyroids in hypophysectomized rats in normocalcaemic and short-term induced...

The ultrastructure of parathyroid glands of hypophysectomized rats in normo- and hypocalcaemic conditions was qualitatively and quantitatively analysed. Parathyroid glands of both intact and hypophysectomized rats comprised cells of similar shape and staining intensity and of an equal number of cells in mitosis. Cell volume was not affected but the surface area of plasma membrane, RER and Golgi complex was increased in parathyroid cells after hypophysectomy. Parathyroid cells of both intact and hypophysectomized rats responded to hypocalcaemia by a drastic increase in surface area of the plasma membrane and a decrease in surface area of the Golgi complex. Since RER, Golgi complex and plasma membrane are concerned with secretion of parathyroid hormone, the data suggest that (1) the pituitary has either no effect on parathyroid cells, or a possibly stimulating effect can be compensated after hypophysectomy, or the pituitary even has a suppressive effect on parathyroid cells, and (2) the responsiveness of parathyroid cells to changes in serum calcium is unimpaired after hypophysectomy.