CAPILLARY PATTERN OF THE THYROID GLAND IN THE RAT IN FUNCTIONAL BLOCK
ABSTRACT The capillary pattern of the thyroid gland was studied in the rat: one group had undergone hemithyroidectomy, one was treated with propyl thiouracil, and one subjected to both these experimental measures. Histological and microangiographic observations were compared with those in an intact control group. Epithelial hyperplasia and other morphological signs of activity were seen to a moderate extent in the hemithyroidectomized group, were marked in the rats treated with thiouracil, and most marked in the group subjected to both thiouracil medication and hemithyroidectomy. The appearances of the interfollicular capillaries showed no perceptible changes in the group subjected solely to hemithyroidectomy. Changes of the interfollicular capillaries were marked in all the animals treated with propyl thiouracil. In the group only treated with propyl thiouracil, the capillaries were dilated to sinusoid-like blood pools in limited segments between which the capillaries were of normal width. In the group subjected to both hemithyroidectomy and propyl thiouracil treatment the interfollicular capillaries were dilated throughout their course. The significance of these morphological and microangiographic observations is discussed.