Quantitative changes in the frequency and distribution of the C-cell population in the rat thyroid gland with age

Abstract

The development of calcitonin cells (C-cells) was investigated in rat thyroid glands from birth to 120 days, using an immunoperoxidase technique and a point-counting method. The proportion of C-cells to follicular cells was 4.5% on the day of birth and increased progressively to 10.4% by 120 days. The highest density of C-cells was noted in the mid-region of the lobes along a longitudinal axis. The caudal and cephalic regions of the lobes contained smaller numbers of C-cells. The C-cells tended to be more numerous in the posterior aspects of the lobes. Although the numbers of C-cells in 120-day-old animal were markedly increased as compared to animals at the time of birth, the cell distributions within the glands were similar at all ages.

Paracrine Regulation of Thyroid-Hormone Synthesis by C Cells

“…Those findings were concordant to those from Volante et al [140] who failed to detect ghrelin-immunopositive cells in normal human adult thyroid gland. This last fact, being probably due to the very scarce presence of C cells in the human adult thyroid gland as compared to rats, where their percentage, in relation to follicular cells, ranges from 4.5 to 10.4% [18]. These observations were supported by the study by Raghay et al in 2006 [38] in which ghrelin was described in the thyroid gland to be synthesized only by C cells.…”

“…The distribution of C cells within the thyroid lobes has also been reported to vary among species. In most species, C cells are located primarily in the centre of thyroid lobes, including humans [15,16], mice [17], rats [18] and rabbits [17]. The area where C cells predominate has been termed as 'C-cell region' [19], which is also the place where the mostactive follicles of the gland predominate [20].…”

“…In humans, C cells comprise less than 1% of the total endocrine-cell population [21], while the proportion of C cells to follicular cells is at least 5% in rats [18]. Furthermore, C cell concentration may vary according to age.…”

“…In humans, however, data are very contradictory: Wolfe et al in 1974 found that the number of C cells per unit area appeared to decrease with age [15], while Gibson et al in 1982 found an age-dependant increase in C cells [16]. In contrast, thyroid glands of adult rodents have clearly more numerous C cells than those of neonates [14,18].…”

Flow sorting from organ material by intracellular markers

“…To allow specific examination of nucleated thyroid cells and exclusion of debris during sorting, TO-PRO-3 staining was used (10). The antihuman calcitonin antibody stained a proportion of rat thyroid cells commensurate with the described C cell frequency in this species (11). The staining could be abrogated by preincubating the antibody with human calcitonin peptide (Fig.…”