title: Heterogeneity of cationic amino acid transport systems in mouse mammary gland and their regulation by lactogenic hormones.
abstract: The mechanism of cationic amino acid transport in lactating mouse mammary gland was investigated. Two Na(+)-independent systems of arginine transport were discriminated on the basis of their sensitivity to leucine. The leucine-sensitive uptake of arginine (Km 0.4 mM) was through a broad specificity system that interacted with both cationic and neutral amino acids, and was inhibited by preloading mammary tissue with neutral amino acids. The leucine-insensitive uptake was identified as the y+ system (Km 0.76 mM). Preloading mammary tissue with cationic amino acids increased the uptake of arginine by the y+ system. Decreasing the pH of the external medium to 6.0 suppressed the y+ system-mediated uptake by approximately 25%, whereas the broad specificity system remained unaffected. Lactogenic hormones upregulated the y+ system-mediated uptake of arginine in pregnant mouse mammary tissue cultured in vitro, although the broad specificity system remained unaffected. The y+ system-mediated uptake increased 2-fold with insulin alone and 4-fold with the combination of insulin, cortisol and prolactin.
authors.affiliation: Division of Animal Biochemistry, National Dairy Research Institute, Haryana, India.
authors.forename: R
authors.initials: R
authors.lastname: Sharma
authors.forename: V K
authors.initials: VK
authors.lastname: Kansal
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000378:metabolism; D001692:Biological Transport; D002412:Cations; D046508:Culture Techniques; D005260:Female; D006706:Homeostasis / Q000187:drug effects*; D006854:Hydrocortisone / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D007930:Leucine / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000378:metabolism*; D051379:Mice; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D002412:Cations; D007328:Insulin; D011388:Prolactin; D001120:Arginine; D012964:Sodium; D007930:Leucine; D006854:Hydrocortisone