Abstract
Summary
Theophylline at 5 × 10-3 M concentration acting for 20 min produced a greater net increase in phosphorylase a activity in isolated estrogen-primed uteri than in uteri from ovariectomized rats. This difference cannot be explained only by the reported elevated amounts of epinephrine in uteri stimulated by estrogen. Theophylline potentiated the effect of epinephrine treatment in vitro to increase uterine phosphorylase a activity but did not potentiate the effect of oxytocin. Pretreatment with reserpine which is reported to lower endogenous catecholamine levels in the uterus, did not decrease the effect of theophylline on the activity of the enzyme. Cyclic-AMP which mediates the effect of catecholamines to inhibit uterine motility and to increase phosphorylase a activity in other tissues, increased the activity of the enzyme only in the estrogen-primed uteri. Theophylline is reported to produce its effect by permitting an accumulation of C-AMP in responsive tissues.
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