In vivo and in vitro evidence for ACh-stimulated L-arginine uptake.
Whereas L-arginine is clearly recognized as the precursor for nitric oxide synthesis, and its entry into endothelial cells via system y(+) transport is established, few data exist regarding the acute regulation of this transport process. We specifically investigated the effect of ACh and isoprenaline (Iso) on L-arginine uptake in the human forearm and in cultured bovine aortic endothelial cells (BAEC). Sixteen healthy males were studied. During a steady-state intra-arterial infusion of [(3)H]L-arginine (100 nCi/min), the effects of ACh (9.25 and 37 microg/min), Iso (25-50 and 200 microg/min), and sodium nitroprusside (SNP) (1-2 and 8 microg/min) on forearm plasma flow (FPF), L-[(3)H]arginine uptake, and L-[(3)H]citrulline release were determined. In parallel experiments, the effects of ACh, Iso, and SNP on L-[(3)H]arginine uptake were studied in BAEC. L-Arginine uptake was inversely related to FPF (r = -0.50; P < 0.005). At a similar FPF (ACh 56.82 +/- 9.25, Iso 58.49 +/- 5.56, SNP 57.92 +/- 4.96 ml/min; P = ns), intra-arterial ACh significantly increased forearm uptake of L-[(3)H]arginine (54,655 +/- 8,018 dpm/min), compared with that observed with either Iso (40,517.23 +/- 6,841 dpm/min; P = 0.01) or SNP (36,816 +/- 4,650 dpm/min; P = 0.011). This was associated with increased ACh-induced L-[(3)H]citrulline release compared with Iso and SNP (P = 0.046). Similarly, in BAEC, ACh significantly increased L-[(3)H]arginine uptake compared with control, Iso, or SNP (ACh 12.0 x 10(7) +/- 1.83 x 10(7) vs. control 6.67 x 10(7) +/- 1.16 x 10(7) vs. Iso 7.35 x 10(7) +/- 1.63 x 10(7) vs. SNP 6.01 x 10(7) +/- 1.11 x 10(7) fmol.min(-1).mg(-1) at 300 micromol/l L-arginine; P = 0.043). Taken together, these data indicate that ACh stimulates L-arginine uptake in cultured endothelial cells and in human forearm circulation, indicating the potential for acute modulation of endothelial L-arginine uptake.
Parnell
Melinda M
MM
Wynn Department of Metabolic Cardiology, Baker Heart Research Institute, PO Box 6492, St. Kilda Rd. Central, Melbourne, Victoria 8008, Australia.
Chin-Dusting
Jaye P F
JP
Starr
Jennifer
J
Kaye
David M
DM
D000109:Acetylcholine / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000328:Adult; D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D001120:Arginine / Q000097:blood* / Q000493:pharmacokinetics*; D002417:Cattle; D002478:Cells, Cultured; D002956:Citrulline / Q000097:blood; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
D000318:Adrenergic beta-Agonists; D020030:Nitric Oxide Donors; D014665:Vasodilator Agents; D009599:Nitroprusside; D002956:Citrulline; D001120:Arginine; D007545:Isoproterenol; D000109:Acetylcholine