ABSTRACT
INTRODUCTION: C cells constitute a small percentage of thyroid gland parenchyma. The number, morphology and distribution of C cells differ among species; however, data regarding their characteristics in European bison are sparse. The aim of this study was to evaluate the morphology, distribution pattern and percentage of C cells in European bison thyroid gland together with morphometric analysis. MATERIAL AND METHODS: Thyroid glands from 28 European bisons of different sex and age were collected either in autumn-winter (13/28) or in spring-summer (15/28) periods and analyzed by immunohistochemistry. RESULTS: The mean total C cell number per all endocrine (follicular and C cells) cell number (C cell concentration) was 7.33%. The tendency to increase the C cell number from periphery to the central region of thyroid lobe was observed with the mean C cell concentration of 3.95%, 7.89% and 9.97% in peripheral, intermediate and central areas, respectively. Most frequently, C cells were situated intrafolliculary whereas epifollicular and interfollicular positions were observed less often. C cells were polymorphic with long cytoplasmic processes. The mean C cell area was 61.97 µm2 and the mean C cell perimeter, length and width were: 34.92 µm, 12.85 µm and 4.91 µm, respectively. In the majority of C cells, strong immunohistochemical cytoplasmic reaction was observed with the mean color intensity of 78.32. In autumn-winter period, C cells were significantly larger with lower color intensity than during spring and summer. CONCLUSIONS: This study leads to deeper characteristics of thyroid gland C cells in European bison. The histomorphometric data suggest that in European bison production of calcitonin by C cells may differ depending on the time of the year.
