HORMONAL EFFECTS ON PHOSPHORYLASE ACTIVITY IN THE RAT UTERUS1

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Abstract
Hormonally induced changes in total phosphorylase t and active phosphorylase a concentrations were determined in the uteri of spayed rats given estridiol and the ratios a/t calculated. A single injection of 50 [mu]g estradiol in rats spayed 6-8 days increases phosphorylase a concentration and the ratio /t at least 2 fold in 48 hours without altering the level of phosphorylase t. The amount of phosphorylase a per whole uterus increases by 6 hours after estradiol, phosphorylase t by 24 hours, indicating 2 phases of the estrogen effect. Phosphorylase a is high at normal estrus, low during diestrum. Testosterone acts similar to estradiol but is less effective and progesterone has no effect. Large doses of adrenaline, nor-adrenaline and posterior pituitary extract given intraperitioneally to estrogen-primed rats, markedly lowers phosphorylase a within 1 hour, but not phosphorylase t. Histamine lowers both slightly without altering the ratio. These changes in phosphorylase a parallel similar changes in uterine glycogen, previously reported.