C cells in the thyroid of pinealectomized rats.

PURPOSE To study quantitatively C cells in the thyroids of non-isogenic rats to determine the possible effects of pinealectomy on the number of these cells, and consequently on the synthesis and secretion of calcitonin. METHODS Twenty male rats of an outbred strain (200-300 g) were used in the present study. One group of 10 animals was pinealectomized 50 days prior to sacrifice. Thyroid tissue was stained for calcitonin (Dako Corporation) at a 1:1500 dilution. The number of C cells observed was expressed as number of cells/cm . Data were analyzed statistically by Mann-Whitney test. RESULTS The number of C cells in pinealectomized and normal animals ranged from 489 to 2084 per cm and 227 to 1584 per cm , respectively, a difference that was statistically significant (P <0.05). CONCLUSIONS These results showed consistent differences in the number of C cells after pinealectomy when compared to controls. We believe that pinealectomy increases the number of C cells in the rat thyroid.