Alpha-aminoisobutyric acid transport in isolated rat submandibular salivary acinar cells.
Na+-dependent alpha-aminoisobutyric acid (AIB) transport by isolated submandibular cell aggregates (pmol min-1 mg protein-1) was greater in the presence than in the absence of insulin, Vmax (5220 compared with 2900). Km (1.78 and 1.40 mM, respectively) was unaffected by insulin. Na+-dependent methyl-aminobutyric acid (MeAIB) transport was also greater in the presence of insulin (V max, 3120 compared with 2010 pmol min-1 mg protein-1; Km, 1.03 and 0.93 mM). In the presence of 10 mM MeAIB, Na+-dependent AIB transport was reduced to 76 pmol min-1 mg protein in both control and insulin-treated cells. The remaining Na+-dependent uptake of AIB was inhibited by 10 mM serine. Na+-independent AIB transport was unaffected by insulin, and in the presence of 5 mM 2-aminobicyclo-[2,2,1]-heptane-carboxylic acid (BCH) AIB uptake was reduced to 10% of that observed under Na+-replete conditions. In the absence of insulin, the rate of Na+-dependent AIB uptake rapidly decayed; however, following the addition of hormone the rate of transport was maintained. Thus in the rat submandibular gland AIB uptake is mediated by at least three transport systems (A, L and ASC), and maintenance of normal system A activity requires insulin.
Anderson
L C
LC
Emory University Dental Research Center, Atlanta, GA 30322.
Mixson
E
E
D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D007328:Insulin / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D013363:Submandibular Gland / Q000166:cytology / Q000378:metabolism*
D000621:Aminoisobutyric Acids; D007328:Insulin; C100049:2-aminoisobutyric acid; C017911:2-(methylamino)isobutyric acid; D012964:Sodium