Hormone-dependent accumulation of rough endoplasmic reticulum in mouse mammary epithelial cells in vitro
Oka, T.; Topper, Y.J.
Journal of Biological Chemistry 246(24): 7701-7707
ISSN/ISBN: 0021-9258 PMID: 4332563 Accession: 005587004
Formation of rough endoplasmic reticulum (RER) by mammary cells cultured for 96 h was studied by measuring membrane-linked NADH-cytochrome c reductase activity and the RNA content of isolated RER. Addition to the incubation medium of 5 micro g insulin (I)/ml, 5 micro g hydrocortisone (H)/ml, I + H or I + H + 5 micro g prolactin/ml respectively caused 44, 130, 360 and 320% increase in reductase activity and 70, 5, 480 and 960% increase in RNA. Corticosterone and aldosterone had similar effects to those of H. Studies of reductase activity and RER formation as a function of time suggested that addition of H to an I-containing postmitotic system caused redistribution of free ribosomes to the membrane-bound variety without net increase in ribosomes. In the absence of H, I promoted development of an unstable RER deficient in reductase. Prolactin did not affect the reductase activity but stimulated rate of RNA synthesis and increased RNA content of RER. In the absence of RER, prolactin stimulation of RNA synthesis was not maintained. Formation of RER precedes casein synthesis by -2 days, the presence of RER and continuous RNA formation being required for casein synthesis. Comparison of casein and RER formation, in the presence of I, H and prolactin, as functions of H concn. showed excellent correspondence between the dose response curves, suggesting that casein formation is dependent on I- and H-induced RER formation.