CYTOLOGICAL APPEARANCES IN THE NORMAL AND ACTIVATED PARATHYROID OF THE RAT

Abstract

SUMMARY 1. The normal and experimental parathyroid of the rat has been studied as follows: (a) histochemical demonstration of nucleic acids; (b) electron microscopy; (c) cell counts and estimations of gland mass from histological preparations. 2. Within a single cell type cytological variation probably reflects functional differences: at one extreme is a cell with expanded endoplasmic reticulum and swollen mitochondria, contrasting with a cell containing compact mitochondria and unexpanded endoplasmic reticulum. 3. Small parenchymal groups have a common cytology different from other groups. 4. A light-dark cell contrast is not an obvious normal feature, although some cells containing slightly more cytoplasmic 'Palade' granules [Palade, 1955] are consequently more electron opaque than others. 5. A simple compensatory hypertrophy (two-fold by the 7th week) of the remaining gland follows unilateral parathyroidectomy. 6. In the parathyroid activated by phosphate administration or bilateral nephrectomy there is a marked dark-light cell contrast. The dark cell greatly predominates and contains a high cytoplasmic concentration of Palade granules besides an expanded endoplasmic reticulum. 7. There is a marked increase in histochemically demonstrable ribonucleic acid (RNA) (cytoplasmic) in the activated parathyroid, and also an increase in cell size. 8. These observations suggest that a state of increased parathyroid activity is associated with: an absolute increase in number of cytoplasmic Palade granules, an expanded endoplasmic reticulum, mitochondrial swelling, intensification of cytoplasmic RNA staining, and an increase in cell size.