Abstract
Summary
Hypophysectomized-ovariec-tomized albino rats weighing 160 g were injected daily for 19 days with 90 GPU of relaxin and/or other mammotropic hormones, including prolactin (25 IU), estra-diol benzoate (1 μg), and progesterone (3 mg). Prolactin alone or in combination did not increase body weight. Mammary wet weight was increased significantly by prolactin, progesterone, and relaxin, but not by other combinations. Relaxin was without effect on mammary wet weight, but syner-gized with prolactin and progesterone to increase mammary dry fat-free tissue. It also synergized with prolactin or prolactin and progesterone to stimulate DNA and RNA of the mammary tissue, but did not increase the ratio of RNA to DNA. It is concluded that relaxin has limited mammo-tropic action by itself, but synergizes effectively with anterior pituitary and ovarian steroid mammotropins to stimulate mammary development.
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