STRUCTURAL CHANGES ASSOCIATED WITH INHIBITION OF INVOLUTION OF THE MAMMARY GLAND IN THE ALBINO RAT

Abstract

SUMMARY Litters were removed from post-parturient rats on day 4 of lactation and the mothers were then treated with various hormones and pharmacological substances. All treatments (oxytocin, reserpine, prolactin (PR), prolactin+ growth hormone (GH), prolactin + adrenocorticotrophin (ACTH)) resulted in a significant retardation of mammary involution. Both oxytocin and reserpine treatment had little effect on the maintenance of the ultrastructure of the mammary epithelial cells, although after reserpine treatment fat droplets were more frequently observed in the epithelial cells. Treatment with PR, PR + GH and PR + ACTH resulted in a progressive maintenance of the ultrastructure of the epithelial cells, with increased fat present in these cells. However, all treatments failed to alter the distribution of the macrophage-like cells and no alteration in the lysosomes was apparent. The factors involved and the mechanisms by which these treatments might have exerted their effect are discussed.