Some morphological changes in the rat thyroid gland during experimental hyperphenylalaninemia.

BACKGROUND: Little is known about the effect of phenylketonuria on the thyroid gland. In the present study, this problem was investigated by using a defined experimental model of hyperphenylalaninemia (HPA). METHODS: The experimental group was subjected to an HPA regimen (Matsuo and Hommes, 1988. Neurochem. Res., 13:867-870) from the 5th day of postnatal development. The pups were decapitated on the 7th, 14th, 21st, 28th, and 35th days. The thyroid glands were fixed in Bouin's fluid and routinely embedded in paraffin. The staining techniques used were Mallory-Slinchenko's method, toluidin blue, silver impregnation of the basement membrane, immunohistochemical staining of the proliferating cell nuclear antigen (PCNA), and neuron-specific enolase (NSE). RESULTS: The size of the follicles was less than that in the control group. There were no substantial changes in the epitheliomer structures. In almost all of the treated groups, a reduction in the number of PCNA+, NSE+, and mast cells was observed until the 28th day. On the 28th day of HPA, the level of mast cell degranulation was higher (61%) than that in the control group. On the 35th day, these parameters began to reach normal levels. From the 28th day, degenerative changes in the thyroid glands of treated animals were observed in the NSE+ cells. CONCLUSIONS: The HPA condition mainly has an influence on the number and structure of the NSE+ cells of the thyroid gland. One may assume that under HPA the increase in mast cell degranulation plays a significant role in the normalisation of the parameter of the thyroid gland.

Histological studies of atrazine toxicity on the thyroid gland in rats.

Little is known about the toxic activity of the atrazine (a herbicide, commonly used in agricultural production) on the thyroid gland. In this study the compound was administered orally in female albino rats at sublethal exposure equivalent to 0.2 LD50 doses for 6 and 12 days. At termination of dosing the anesthetized animals were killed and blood was drawn for the determination of serum triiodothyronine (T3) and thyroxin (T4). A dose-dependent decrease of serum T3 concentration was observed in all the groups (control: 0.57 nmol-L-1; 6 days: 0.35 nmol-L-1; 12 days: 0.21 nmol-L-1). The thyroid gland was examined light-microscopically. Bouin's solution-fixed thyroids were embedded in paraffin and sections cut at 6 microns, stained separately with toluidine blue according to Slinchenko's method. Histologically in experimental groups epithelium featured small cuboidal cells and occasional structures of the follicles confluence within epitheliomers. A dose-dependent changes of the following parameters were observed: (a) increasing of number of follicle-building thyroid cells; (b) increasing of follicular volume; (c) decreasing of nucleus volume. Investigation of the whole population of thyroid mast cells disclosed no change in degranulation intensity. By contrast, degranulation intensity was decreased in perifollicular mast cells from groups treated with atrazine in dose-dependent manner. There are no changes observed in degranulation of stromal mast cells. These results suggesting that differences in response to the atrazine might account for an aspect of the functional heterogeneity within the rat thyroid mast cell population.