Insulin stimulates cationic amino acid transport activity in the isolated perfused rat pancreas.
The effects of exogenous insulin, glucagon and streptozotocin-diabetes on influx (15 s) of L-lysine via a cationic amino acid transporter resembling system y+ were investigated in the isolated perfused rat pancreas. In non-diabetic pancreata, transport of L-lysine was saturable with an apparent Km of 2.11 +/- 0.29 mM and Vmax of 2.21 +/- 0.20 mumol min-1 g-1 (n = 6). Bovine insulin (100 mu u ml-1) increased the maximal transport rate (Vmax = 3.49 +/- 0.30 mumol min-1 g-1, n = 4, P < 0.05) for L-lysine 1.6-fold without altering the Km. L-Lysine transport was not elevated significantly in diabetic pancreata, although insulin (100 mu u ml-1) enhanced transport to values measured in non-diabetic preparations. Human glucagon (1.5 x 10(-9) M) had no stimulatory effect on L-lysine transport. These findings provide the first evidence that exogenous insulin stimulates cationic amino acid transport activity in the exocrine pancreatic epithelium. Activation of the cationic pancreatic amino acid transporter may provide a mechanism to enhance the supply of L-arginine and thus sustain nitric oxide-mediated pancreatic secretion in response to islet hormones and secretagogues.
Muñoz
M
M
Biomedical Sciences Division, King's College London, UK.
Sweiry
J H
JH
Mann
G E
GE
D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D005765:Gastrointestinal Agents / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008239:Lysine; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical
D000596:Amino Acids; D005765:Gastrointestinal Agents; D007004:Hypoglycemic Agents; D007328:Insulin; D005934:Glucagon; D008239:Lysine