CHRONIC HYPERVITAMINOSIS D-3 DETERMINES A DECREASE IN C-CELL NUMBERS AND CALCITONIN LEVELS IN RATS

Many papers have reported that chronic hypercalcemia induced either by large doses of vitamin D or by the administration of calcium or parat hormone, produces hypertrophy and hyperplasia of C cells. However, mor e recent studies suggest that the effect of elevated calcium or 1.25(O H)(2)D-3 concentration on the production of calcitonin may be more com plex than previously suspected. To assess the validity of such a respo nse an experimental model, where hypercalcemia was induced with vitami n De overdose, was designed. Male Wistar rats were administered vitami n D-3 chronically (50,000 IU per 100 ml of drinking water with or with out CaCl2). Serum calcium and calcitonin levels were determined. C cel ls were stained by immunohistochemistry using calcitonin and neuronal specific enolase (NSE) antibodies and their percentage was calculated by a morphometric analysis. We also investigated the ultrastructural c haracteristic of the C cells under experimental conditions. C cells di d not have a proliferative response rather a decrease in their number was observed after 1 month of treatment with 25,000 IU of vitamin D-3 (1.55 vs 2.43% in control animals) and 3 months with vitamin plus CaCl 2 (2.27% vs 3.62% in control animals). In addition, no significant cha nges in serum calcitonin levels were observed during the experimental period. We conclude that rat C cells do not respond with hypertrophic and hyperplastic changes in a hypercalcemic state due to an intoxicati on with vitamin D-3. (C) 1998, Editrice Kurtis.