Rekha Sharma

Heterogeneity of cationic amino acid transport systems in mouse mammary gland and their regulation by lactogenic hormones.

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.

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

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.

Mechanism of glycine transport in mouse mammary tissue.

The mechanism of glycine transport in lactating mouse mammary gland was investigated. Three Na+-dependent systems of glycine transport, distinguished on the basis of their ionic requirement and sensitivity to 2-(methylamino)isobutyric acid (MeAIB), were A (Na+-dependent, MeAIB-sensitive); (Na++Cl-)-dependent, MeAIB-insensitive; and Na+-dependent, Cl--independent, MeAIB-insensitive. These systems were further distinguished on the basis of inhibition analysis and sensitivity to pH of the extracellular medium and preloading mammary tissue with amino acids. The uptake of glycine via the A system (Km 0.53 mM) was inhibited by preloading mammary tissue with alanine, while glycine uptake mediated by the (Na++Cl-)-dependent, MeAIB-insensitive system (Km 0.47 mM) was downregulated by preloading mammary tissue with all amino acids (alanine, sarcosine and histidine) tested. Treatment of mammary tissue with N-ethylmaleimide inhibited the uptake of glycine via both these systems. Decreasing the pH of the extracellular medium inhibited the uptake of glycine via the A system but not the (Na++Cl-)-dependent, MeAIB-insensitive system. On the basis of ionic requirement, system A appears to comprise two components, one dependent on Na+ plus Cl- and the other on Na+ alone. Insulin upregulated the A system-mediated uptake of glycine in pregnant mouse mammary tissue cultured in vitro, while the (Na++Cl-)-dependent, MeAIB-insensitive system remained unaffected.

Confirmation of buffalo tallow in anhydrous cow milk fat using gas liquid chromatography in tandem with species-specific polymerase chain reaction

Confirmation of buffalo tallow in anhydrous cow milk fat (cow ghee) is a major problem to date. In the present investigation, a novel strategy has been developed to detect and confirm the buffalo tallow in cow ghee. It involved coupling the gas liquid chromatography (GLC) of triglycerides with the rapid species-specific polymerase chain reaction (PCR) to confirm the presence of buffalo tallow in anhydrous cow milk fat. Adulteration of cow ghee with buffalo tallow at 10% level could be confirmed using the standardised protocol. The standardised protocol can help in countering the cases of cow ghee adulteration with buffalo tallow.