Characteristics of alpha-aminoisobutyric acid transport by lactating rat mammary gland.
The transport of alpha-aminoisobutyric acid (AIB) by lactating rat mammary tissue has been examined. AIB uptake by mammary tissue was via both Na(+)-dependent and Na(+)-independent pathways. AIB uptake via the Na(+)-dependent pathway was inhibited by (methylamino)isobutyric acid (MeAIB) whereas AIB uptake via the Na(+)-independent pathway was blocked by 2-aminobicyclo[2,2,1]-heptane-2-carboxylic acid (BCH). A small fraction of AIB influx persisted in the presence of both MeAIB and BCH. The Na(+)-independent moiety of AIB uptake was strongly inhibited by phenylalanine, tryptophan, leucine, isoleucine and methionine. AIB efflux from mammary tissue slices was found to be both Na(+)-dependent and Na(+)-independent. Trans-stimulation of AIB efflux by other amino acids was not observed; in contrast, external phenylalanine, tryptophan and leucine inhibited AIB efflux. The results are largely consistent with the presence of systems A and L in lactating rat mammary tissue. However, the Na(+)-independent fraction of AIB transport may represent transport via a tissue specific form of system L.
Shennan
D B
DB
Hannah Research Institute, Ayr, UK.
McNeillie
S A
SA
D000596:Amino Acids / Q000494:pharmacology; D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005260:Female; D007700:Kinetics; D007774:Lactation / Q000502:physiology*; D007930:Leucine / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D010649:Phenylalanine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology; D014364:Tryptophan / Q000494:pharmacology; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000494:pharmacology
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; C100049:2-aminoisobutyric acid; C006504:2-aminobicyclo(2,2,1)heptane-2-carboxylic acid; D010649:Phenylalanine; D014364:Tryptophan; D012964:Sodium; D007930:Leucine