Maciej Zabel

Immunocytochemical Studies on Thyroid Parafollicular Cells in Postnatal Development of the Rat

Studies were performed on Wistar strain rats aged 1-720 days. Immunocytochemical reactions were used to detect calcitonin, somatostatin, calcitonin gene-related peptide (CGRP), cholecystokinin, serotonin, neuron-specific enolase (NSE), secretory protein-I, chromogranin and Ca-binding protein. In the parafollicular cells of the rat, the presence of calcitonin, somatostatin, CGRP, NSE and secretory protein-I could be demonstrated. The number of parafollicular cells increased with the age of animals, and the increase was particularly pronounced in the early postnatal period and after the first year of age. The number of somatostatin-immunoreactive cells decreased after birth and increased again after the first year of age. The number of calcitonin-immunoreactive cells increased in the early postnatal period independently of the increase in parafollicular cell number, forming frequently tumor-like outgrowths in 2-year-old animals. A small proportion of these outgrowths contained no calcitonin even if they did contain somatostatin, CGRP and NSE immunoreactivity. Evident changes in immunoreactivity in the first days after birth may reflect the sudden change in environment and may be associated with growth and differentiation. In any period of life, CGRP- and NSE-immunoreactive cells have constituted the most numerous groups and, therefore, the respective antigens seem to represent the most suitable markers of parafollicular cells in the rat.

Immunocytochemical studies on parafollicular cells of various mammals.

Using specific antisera, calcitonin, calcitonin gene-related peptide (CGRP), somatostatin as well as neuron-specific enolase, chromogranin, secretory peptide I and calbindin (vitamin D-dependent calcium-binding protein) were looked for in parafollicular cells of rats, Syrian hamsters, Mongolian gerbils, mice, guinea pigs, rabbits and pigs. Calcitonin and CGRP were most invariably present in various species. Somatostatin was absent in mice and Mongolian gerbils and present in variable amounts in the remaining species. Neuron-specific enolase could not be detected in rabbits, while in the pigs and the Mongolian gerbils it could be demonstrated only in some parafollicular cells. Calbindin was present exclusively in parafollicular cells of guinea pigs. Chromogranin and secretory protein-I were present only in some animal species.

Studies on localization of calcitonin gene-related peptide (CGRP) in the thyroid-parathyroid complex

Calcitonin gene-related peptide (CGRP) was localized by an immunocytochemical technique in the thyroid-parathyroid complexes of rat, guinea pig, rabbit, and in normal human thyroids and parathyroids. Human medullary carcinomas and parathyroid adenomas were also studied. In man and all animal species examined CGRP was present in the parafollicular cell, however, in guinea pigs only in small amounts. Except in rabbits, presence of CGRP was demonstrated in nerves of the thyroid and parathyroid capsule as well as in the nerve fibers of the capsular blood vessels. In the thyroid of guinea pigs CGRP was also noted in nerve fibers and in blood vessel walls between follicles. CGRP was also present in the parathyroid glands of rat and man, in nerve fibers localized between parathyroid cells. In rabbit the parafollicular cells between parathyroid cells also expressed CGRP immunoreactivity. No CGRP was noted in the parathyroids of the guinea pig. The proximity of parathyroid cells and CGRP containing tissue structures suggests a role for CGRP in the modulation of parathyroid hormone secretion. The importance of these regulatory mechanisms appear to be different in individual species.

S-100 protein and neuron-specific enolase in parathyroid glands and C-cells of the thyroid

SummaryNormal parathyroid glands and parafollicular cells (C-cells) of man, rat and rabbit, and also human parathyroid adenomas and medullary carcinomas were investigated for the presence of S-100 protein and neuron-specific enolase (NSE). For determination of the proteins immuno-peroxidase methods were applied, i.e., the PAP method and the avidin-biotin system. The antisera, of polyclonal origin, were specifically directed against cow S-100 protein and rat or bovine NSE. The respective antisera are known to crossreact with S-100 protein from man, rat, and rabbit, as well as with NSE from man and rat. Surprisingly, the test for S-100 protein was found to be strongly positive in the parathyroid glands of rat and rabbit and was focally positive in normal and adenomatous human parathyroid glands, but completely negative in C-cells and medullary carcinoma cells. NSE was present in C-cells of rat and man, and in medullary carcinoma cells, but was absent in normal and adenomatous parathyroid cells. The results support data that indicate that both parathyroid cells and C-cells are derived from elements of the neural crest, but undergo different maturation processes during embryological development.

Immunocytochemical study of the distribution of S-100 protein in the parathyroid gland of rats and guinea pigs

SummaryThe distribution of S-100 protein in the parathyroid cells of normal and hypercalcaemic rats and guinea pigs was investigated. Previous studies had shown that the applied antibodies detect only the β subunit of S-100 protein. S-100 protein was found in all parathyroid cells of rats aged between 1 and 720 days. In adult guinea pigs, S-100 protein was detectable in only a small proportion of parathyroid cells. The level of S-100 protein in individual cells exhibited considerable variation, particularly in guinea pigs. Hypercalcaemia did not affect the distribution of S-100 protein in the parathyroid cells of either rats or guinea pigs. In both species, the presence of small groups of parathyroid cells in the central fragments of thyroid lobes was often noted.

Effect of hypercalcemia on parafollicular cells in the rat thyroid gland.

SummaryHypercalcemia was induced in rats by the administration of A.T.10. We then determined the levels of total and ionized calcium and calcitonin in the serum, as well as performed ultrastructural observations and histochemical investigations of the calcitonin and neuron-specific enolase immunoreactivities in the stimulated parafollicular cells. The main aim of the study was to apply histochemical procedures to determine the immunoreactions of calcitonin gene-related peptide (CGRP), somatostatin and secretory protein-I in stimulated parafollicular cells. Immunoreactions of CGRP and calcitonin decreased strikingly in A.T.10-treated animals, whereas no visible changes were noted in somatostatin immunoreactivity. In the case of secretory protein-I, an insignificant increase of its immunoreactivity was observed in the treated animals. The cytophysiological significance of these results is discussed.

Ultrastructural immunocytochemical localization of calcitonin in the C cells of the rat thyroid

SummaryUsing unlabeled antibodies and peroxidase-anti-peroxidase complexes, calcitonin was localized at the ultrastructural level in rat thyroid C cells. Calcitonin was present mainly in secretory granules of the cells. A less intense positive reaction was noted in the cytoplasm surrounding the secretory granules.

Studies on in vitro effect of serotonin on calcitonin secretion by rat thyroid C cells

SummaryThyroid glands of young rats were incubated for 3 h in Eagles solution supplemented with 5-hydroxy-l-tryptophan (5-HTP) or with serotonin. Following control incubations or incubations with serotonin, no serotonin could be demonstrated in C cells using immunocytochemical techniques. However, serotonin was demonstrated in the secretory granules of all C cells following incubation with 5-HTP. The secretory function of C cells was evaluated by ultrastructural and immunocytochemical studies, and by calcitonin radioimmunoassays of the incubation medium. Following incubation with 5-HTP, the secretory function of the majority of C cells was inhibited, and calcitonin levels in the media were decreased. Incubation with serotonin produced an increased secretory function of C cells and higher calcitonin levels in the media. The results indicate that serotonin and its direct precursor, 5-HTP, affect calcitonin secretion by rat thyroid C cells by distinct mechanisms.

Ultrastructural localization of calcitonin in control and stimulated thyroid C cells of the rat using protein A-gold immunocytochemical technique.

SummaryUsing anti-human calcitonin serum and a protein !-gold technique, calcitonin was localized at the ultrastructural level in control and calcium gluconate-stimulated thyroid C cells of the rat. In control rats calcitonin was dedected within a majority of the secretory granules while in experimental animals it was demonstrated also within prosecretory granules present in Golgi apparatus.

IMMUNOCYTOCHEMICAL STUDY OF PARAFOLLICULAR CELLS OF THE THYROID AND ULTIMOBRANCHIAL REMNANTS OF THE EUROPEAN BISON

The aim of the present study was to compare parafollicular cells in the bison thyroid and its ultimobranchial remnants. The thyroid of 26 European bisons was fixed in Bouins fluid, 5 microns thick paraffin sections were stained with hematoxylin and eosin. Azan or silver Grimelius methods. For immunocytochemical analysis specific rabbit antisera were used against human calcitonin (CT), human calcitonin gene-related peptide (CGRP), bovine (b) or rat (r) neuron-specific enolase (NSE), human synthetic somatostatin (ST), and porcine chromogranin. Strongly positive reactions in the majority of parafollicular cells were observed after application of antisera against CT, CGRP, bNSE and rNSE only. ST-immunopositive cells were found in small numbers. Immunopositive parafollicular cells were also present outside typical structures of the thyroid within persistent ultimobranchial remnants. In persistent ultimobranchial bodies, parafollicular cells were frequently observed in groups between ultimobranchial follicles in form of solid cell nests. Many of these cells did not react with any of the antisera used and showed features of immature cells. It is concluded that histomorphologic analysis and immunocytochemical examination reveals a heterogeneous population of parafollicular cells in the bison thyroid, and this heterogeneity was particularly clear in persistent ultimobranchial bodies.