Freeze-etching studies on ultrastructural changes of endothelial cells in the thyroid of normal, TSH-treated and Thyradin-treated mice

Abstract

Freeze-etching images of the capillary endothelium in the thyroid of normal, TSH-treated and Thyradin (powdered thyroid)-treated mice were examined. Numerous pores represent vesicular stomata or fenestrations. The number of the pores and their population density are increased in TSH-treated mice, and decreased in Thyradin-treated animals. In addition, the width of the parajunctional zone and of the flat ray free from endothelial pores is smaller in TSH-treated mice and larger in Thyradin-treated animals. These facts indicate that the number of endothelial pores changes according to the functional activity of the gland.

Three-dimensional imaging of blood vessels in thyroids from normal and levothyroxine sodium-treated rats.

“…We previously reported in the Thyradin-treated mice that the number and population density of the endothelial f enestrations of the thyroid capillaries markedly decrease (ISHIMURA et al, 1976). The present findings in the hypofunctional state of the thyroid are morphologically opposite those of the hyperstimulated thyroids showing the higher distribution (population density) and dilatation of the blood capillary reported by us previously (IMADA et al, 1986).…”

“…The thyroid function itself is suppressed by the thyroxine-treatment owing to the negative feedback mechanism. In the hypofunctional thyroid, it is known that the follicular epithelial cell is attenuated and its cytoorganelles are markedly reduced (FuJITA and SUEMASA,1968), and that the capillary endothelial f enestrations are reduced in number and population density (IsHIMURA et al, 1976). In a previous paper, we reported changes in the three-dimensional microvascular architecture, such as the dilation and fusion of the blood~c pillaries, in the hyperfunctional state of this organ (IMADA et al, 1986).…”

Freeze-Etching Images of Capillary Endothelial Pores in the Liver, Thyroid and Adrenal of the Mouse

“…Fenestrated capillaries of several organs have been examined using this method by FRIEDERICI (1968, 1969), MAUI. (1971), SIMIONESCU et al (1974), FUJITA et al (1975), ISHIMURA et al (1976 and YAMAMOTO et al (1976).…”

Cytochemical aspects on the secretion mechanism of the thyroid gland.

“…They are increased in TSH-treated mice which are in a hyperactive state and decreased in Thyradin (thyroid powder)-treated animals which are in a lower active state (17) . It is considered that the endothelial fenestrations are changed in number and population density according to the functional activity of the gland .…”