Thyroid calcitonin cells and parathyroid gland of the Indian rhesus monkey Macaca mulatta in response to experimental hypercalcaemia.

Rhesus monkey (Macaca mulatta) were subjected to hypercalcaemia by daily intramuscular injections of vitamin D2 (100,000 IU) and by providing them gram soaked in 1% CaCl2 solution for eating and 1% CaCl2 solution (prepared in tap water) for drinking. After 10, 15, 20 and 30 days of such treatment the serum calcium level recorded a rise (18.24 +/- 0.56, 26.20 +/- 1.30, 17.25 +/- 0.25 and 20.50 +/- 0.55 mg/dl respectively) as compared to those of control animals (12.80 +/- 1.00, 12.30 +/- 0.50, 12.70 +/- 0.20 and 12.30 +/- 0.30 mg/dl). Serial sections of thyroid parathyroid complex and isthmus were subjected to selective staining for lcalising the C cells. The structure and behaviour of these cells both under normal and experimental conditions has been studied. Hypercalcaemia resulted in the increase of these cells. Mitotic figures of the C cells were also encountered after 10 days of hypercalcaemia. The specimens subjected to 30 days treatment showed complete degranulation of these cells. Chronic hypercalcaemia inhibits the activity of parathyroid cells which display degenerative changes. The anterior and posterior poles, the peripheral regions of thyroid and isthmus are completely devoid of calcitonin cells.