The influence of the estrous cycle on the accumulation of 3H-noradrenaline in rat uterus and on efflux of radioactivity from the uterus.

Groups of female rats were used throughout the 4-days estrous cycle and the accumulation of noradrenaline and its efflux were studied after incubation with the labelled amine. Comparisons were made between uterine horns corresponding to each one of the 4 stages of the cycle, i.e., diestrus, proestrus, metestrus and estrus. Accumulation in diestrus reached the highest value, which was 1.64-fold higher than in estrus. An estimate of the original distribution of the amine into the extraneuronal and neuronal compartments of the tissue was obtained by compartmental analysis of the efflux curves. Size and half times of neuronal and extraneuronal compartments showed some relationship with the stage of the cycle.