Abstract
Summary
Mammary gland growth comparable to that occurring during normal pregnancy was induced in ovariectomized rats by daily injection of 2 μg EB + 6 mg P for 19 or 24 days. GH, LGH and HCA were then injected separately and in combination for 3 days. These hormones stimulated significant increases in mammary gland growth as measured by DNA/100 g BW. 1.5 mg GH increased DNA to 9.05 mg/100 g while 2 mg GH + 500 μg HCA increased DNA to 9.15 mg/100 g. This latter value is 47% greater than EB + P at day 24. It is only 15% less than DNA value at day 3 of lactation. All hormones stimulated lactogenesis but GH was less effective than the other 2 hormones. It was concluded that ovarian hormones (EB + P) play a dominant role in preparturient growth, whereas GH and HCA play dominant roles in “lactational growth” of rat.
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