The fine structure of uterine smooth muscle of the rat uterus at various time intervals following a single injection of estrogen.

Abstract

AbstractThe fine structure of smooth muscle cells of the rat uterus was studied at 6, 12, 24, 48, 72 and 96 hours after a single subcutaneous injection of estradiol dipropionate (10 μg). The control rats were ovariectomized, but did not receive hormone treatment. Changes in the ultrastructure of the muscle cells occurred soon after estrogen stimulation. An increase in the number of ribosomes on the outer nuclear membrane and evagination of the membrane into the surrounding cytoplasm was noted at six hours. The amount and dilatation of the granular endoplasmic reticulum (GER) increased gradually from 6 to 96 hours. At 24 and 48 hours the mitochondria appeared to increase in number and at later time intervals they increased in size. The Golgi complex was more prominent at 72 and 96 hours than at the earlier time intervals. An increase in free ribosomes was observed at 6 and 12 hours, but a marked accumulation of them occurred at 24 hours and continued to 96 hours. The glycogen granules were very pronounced at 24 and 48 hours with a reduction at 72 and 96 hours. Many pinocytotic vesicles and dense bodies were present in the controls and at 6 and 12 hours. A decrease in number occurred in both at the later time intervals. Organelles accumulated at the nuclear poles beginning at 24 hours and extending to 96 hours. The observations made provide additional information on the fine structure of uterine smooth muscle cells following estrogen stimulation and support previous biochemical studies on glycogen concentration and RNA synthesis in the rat uterus.