Activity of thyroid parafollicular (C) cells in rats with hyperthyroidism--immunohistochemical investigations

The aim of this study was an evaluation of the activity of parafollicular (C) cells in a rat experimental model of hyperthyroidism, evoked by an intraperitoneal application of L-thyroxine (40 mg/kg daily) over 15 days. For that reason, immunohistochemical investigations and evaluation of calcitonin (CT) plasma concentrations were performed. Differences in the quantity and distribution, together with enhanced CT-immunoreactivity of C cells, were observed in hyperthyroid rats, in comparison to respective values in the control group, accompanied by a significant diminution of plasma TSH and CT levels. Our preliminary study may point to a functional interaction between follicular and parafollicular cells in the thyroid gland.