Abstract
Summary
Galactophores of the right 6 mammary glands of rats were ligated on day 3 postpartum and litters were adjusted to contain either 3, 6, 9 or 12 pups. Mammary glands on left side were not ligated. Rats nursing 6 young but without galactophore ligation served as controls. Animals were sacrificed on day 14 postpartum and DNA content of both left and right abdominal–inguinal glands was determined. The posterior pair of pectoral glands was used for histological study. In galactophore-ligated rats, ligated glands were significantly smaller than contralateral non-ligated glands. DNA content of ligated glands of rats nursing 12 young was similar to that of corresponding control glands whereas DNA content of glands of rats nursing 3–9 young was less than control glands. In animals with galactophore ligation, non-ligated glands were significantly larger than corresponding glands of rats without galactophore ligation. It appears that the strength of the suckling stimulus is directly related to maintenance of the mammary parenchyma during lactation.
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