[Morphometric analysis of the parathyroid glands and thyroid gland C-cells during prolonged administration of triiodothyronine and mercazolyl].

The aim of the study was to perform a systemic morphometric analysis of the parathyroid glands and parafollicular thyrocytes under the conditions of the suppression of function of the thyroid follicular apparatus. Water suspensions of triiodothyronine and methniasole were administered through a probe for 24 days to adult albino male rats (6 in each group) at daily doses of 50 micrograms/kg and 6 mg/kg respectively; 6 animals were controls. The level of total calcium in the blood serum of animals in the study groups did not differ from control values. The administration of the drugs induced the development in the parathyroid glands of morphological signs of their increased function (hypertrophy of the parathyrocytes, their nuclei and cytoplasm in both series of experiments, an increase in the mean count of nucleoli in the nucleus in the administration of triiodothyronine). Signs of elevated secretory activity of the population of parafollicular thyrocytes (a decrease in the relative frequencies of C-cells with the cytoplasm filled in with secretory granules; an increase in the proportion of cells with cytoplasmic zones at the vascular poles free of granules) were detected in the thyroid.