Characteristics of transport systems of L-alanine in mouse mammary gland and their regulation by lactogenic hormones: evidence for two broad spectrum systems

• Published in: Journal of dairy research 1999-08, Vol.66 (3), p.385-398
• Main Authors: SHARMA, REKHA, KANSAL, VINOD K.
• Format: Article
• Language: English
• Subjects: Alanine - metabolism; Amino Acids - pharmacology; Amino Acids, Cyclic; Animals; beta-Alanine - analogs & derivatives; beta-Alanine - pharmacology; Biological and medical sciences; Biological Transport - drug effects; Chlorides - pharmacology; Culture Techniques; Female; Fundamental and applied biological sciences. Psychology; Hydrocortisone - pharmacology; Hydrogen-Ion Concentration; Insulin - pharmacology; Kinetics; Mammary Glands, Animal - metabolism; Mice; Mother. Fetoplacental unit. Mammary gland. Milk; Pregnancy. Parturition. Lactation; Prolactin - pharmacology; Sodium - pharmacology; Vertebrates: reproduction
• ISSN: 0022-0299; 1469-7629
• DOI: 10.1017/S002202999900357X

The characteristics of the transport systems of L-alanine in lactating mouse mammary gland and their regulation by lactogenic hormones have been studied. L-alanine uptake was mediated by three Na+-dependent and one Na+- independent systems. The 2-(methylamino)isobutyric acid-sensitive component of Na+-dependent uptake exhibited the usual characteristics of system A. Cl− dependency has been established for system A. The other two Na+-dependent systems, which we have named BCl−-dependent and BCl−-independent, are described for the first time. These are systems with broad specificity and were distinguished on the basis of inhibition analysis, Cl− dependency and the effect of preloading mammary tissue with amino acids. The Na+-independent route was identified as system L, which operates independent of Cl−. The A, L and BCl−-independent transport systems were upregulated in pregnant mouse mammary tissue cultured in vitro in the presence of lactogenic hormones (insulin plus cortisol plus prolactin). Insulin alone also upregulated systems A and L to some extent in pregnant mouse mammary tissue. BCl−-dependent activity was not detected in pregnant mouse mammary tissue and was not induced by lactogenic hormones in vitro.