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Department of Dairy Husbandry, University of Missouri, Columbia
ABSTRACT
The synergistic effect of insulin upon mammary gland growth has been studied in adult ovariectomized rats stimulated with estradiol benzoate (EB) and progesterone (P) for 19 days. When one, two, and three units of insulin were added, mean DNA's/100 g body weight (bw) were increased 8%, a nonsignificant increase; 17%, a significant increase; and 32%, a highly significant increase, respectively, when compared with the control group. A group of 21 rats were ovariectomized, treated with alloxan, then 2 Ég EB + 6 mg P were administered daily to stimulate growth of the lobule-alveolar system of the mammary gland. The mean DNA of the glands was 4.5 mg/100 g bw, a reduction of 18%, a nonsignificant decrease, below the DNA of a control group without alloxan. A second group of 27 similar ovariectomized rats were treated with alloxan. They were injected with the ovarian hormones plus three units of insulin for the same period. The mean DNA of this group was 7.45 mg/100 g body weight, a highly significant increase of 66% in comparison with the group without insulin. Thus, the important role of insulin has been shown by its deficiency and by replacement therapy.
1 Contribution from the Missouri Agricultural Experiment Station Journal series no. 2901-2909. Approved by the Director. This investigation was supported in part by a grant from the USPHS.
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