Abstract
Summary
Hormone-dependent, regressing mammary tumors in rats were incubated in a chemically defined culture medium containing tritium labeled leucine at 37° for 2 hr.
The rate of tritium incorporation into the protein fraction by these tissues was measured with and without the addition of 17β estradiol and/or ovine prolactin into the medium. Tumor tissue responded to either estrogen or prolactin by a 6-7 % increase in the rate of 3H-leucine incorporation. When the incubation medium contained both hormones, the increase in the rate of 3H-leucine incorporation was 19% which was significantly greater than the sum of the effect of each single hormone measured independently. These results demonstrate a synergistic effect between estrogen and prolactin on rat mammary tumors.
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