Ultrastructural observations on the parathyroid glands of the hen (Gallus domesticus).

Abstract

The parathyroid gland of the laying hen, Gallus domesticus, was studied in the electron microscope. The parathyroid gland was comprised of a single cell type, the chief cell. Most of the chief cells contained a small amount of glycogen granules, numerous aggregated ribosomes, abundant mitochondria, cisterns of granular endoplasmic reticulum occurring close to the mitochondria, well developed Golgi apparatus and numerous secretory granules. Prosecretory granules (50-100mμ in diameter) enclosed in a loosely fitting membrane occurred numerously in and near the Golgi field.Secretory granules (200-400mμ in diameter) were round and homogeneously dense bodies were bounded by a limiting membrane. Some granules were seen in the vicinity of, or even in contact with the plasma membrane. The granule content composed of finely granular, electron dense materials was sometimes continuous to the intercellular space through an opening in the fused limiting and plasma membranes. Irregularly shaped dense masses presumably corresponding to the granule content were occasionally seen in widened portions of intercellular spaces. It was thus considered that the secretory granules may be released by eruptocrine secretion.Round bodies (200-400mμ in diameter) containing heterogeneously dense structures seem to be derived from secretory granules and to be lysosomal in nature. These bodies may be involved in the control mechanism of secretion.