Effect of prolactin on phosphate transport and incorporation in mouse mammary gland explants.
Inorganic phosphate is present in milk at a concentration that is severalfold higher than in maternal plasma. In cultured mammary tissues from 12- to 14-day-pregnant mice, the intracellular concentration of (32)PO(4) was six times higher than in the culture medium after a 4-h treatment with (32)PO(4). Of the principal lactogenic hormones [insulin (I), cortisol (H), and prolactin (PRL)], only I and PRL (in the presence of H and I) stimulated (32)PO(4) uptake into cultured mammary tissues; H, by itself or in the presence of I or PRL, inhibited (32)PO(4) uptake. All three lactogenic hormones together effected the greatest stimulation of (32)PO(4) uptake. Similar hormone effects were observed with regard to (32)PO(4) incorporation into lipids and trichloroacetic acid-insoluble molecules. In a time course study, the onset of the PRL stimulation of (32)PO(4) uptake and incorporation occurred 8-12 h after PRL addition; in dose-response studies, the PRL effect was manifested with PRL concentrations of 50 ng/ml and above. From kinetic studies, the apparent maximal velocity of PO(4) uptake was determined to be approximately 7.7 mM x h(-1) x l cell water(-1); the apparent Michaelis-Menten constant was approximately 3-5 mM. The PRL effect on (32)PO(4) uptake was abolished when sodium was absent from the uptake medium. These studies thus demonstrate a complex interaction of three hormones (I, H, and PRL) in the regulation of (32)PO(4) uptake and incorporation into macromolecules in cultured mouse mammary tissues.
Rillema
James A
JA
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA. jrillema@med.wayne.edu
D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006854:Hydrocortisone / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D010710:Phosphates / Q000378:metabolism* / Q000493:pharmacokinetics; D011388:Prolactin / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology; D013997:Time Factors
D007328:Insulin; D010710:Phosphates; D011388:Prolactin; D012964:Sodium; D006854:Hydrocortisone