EVIDENCE FOR THE ACTIVE TRANSPORT OF EPINEPHRINE AND NOREPINEPHRINE BY THE UTERUS OF THE RAT

¹ Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota

The mechanism by which the uterus takes up catecholamines was investigated in vitro using uterine segments or slices. The capacity of the uterus to concentrate dl-norepinephrine-H³ or dl-epinephrine-H³ was determined under a variety of conditions. The catecholamines were taken up against an apparent tissue concentration gradient, and uptake was inhibited by fluoride, ouabain, p-hydroxymercuribenzoate and dinitrophenol, or by incubation at low temperature or anaerobically. The slice-medium ratio was highest for immature uteri and lowest for estrous uteri, and was found to be inversely proportional to the uterine weight. The calculated uptake per uterus was independent of total uterine weight, and it approached a maximum as the concentration of catecholamine increased. The results of the study suggest that epinephrine and norepinephrine can be transported actively by the uterus. The kinetics of transport suggest that small changes in the ratio of epinephrine to norepinephrine in the plasma could alter the relative uptake of these two amines by the uterus in vivo, and thus change the relative amounts of these amities in the uterus.