Studies of calcitonin cells and parathyroid glands of the Indian palm squirrel, Funambulus pennanti in response to experimental hypercalcaemia.

Long term hypercalcaemia was induced in F. pennanti by alternate day intramuscular injections of 50,000 IU of vitamin D2 and by giving them 1% CaCl2 solution prepared in tap water to drink. The controls were not injected with vitamin D2 and were given tap water. The serum calcium levels at various stages of the experiment (1-29 days) show increased values as compared with those of control animals. The calcitonin cells in the treated animals generally exhibit an increase in their number up to the 15th day. Mitotic figures are also encountered between the 7th and the 15th day of treatment. This exhibits the increase in the number of C cells. Constant calcium challenge results in increased quantities of secretory granules among these cells up to the 15th day and in degranulation from the 17th day onwards. It also causes degenerative changes in a certain number of C cells. The parathyroids exhibit atrophic changes (25 days onwards) due to chronic hypercalcaemia. For short term hypercalcaemia, animals were injected intravenously with 1 ml of 10% solution of calcium gluconate. The calcitonin cells do not exhibit any change during the first half hour but thereafter they exhibit progressive degranulation, resulting in marked degranulation after 5 hours of the injection. The parathyroids remain unaffected throughout the experiment and show no histological change.