Essential role of L-arginine uptake and protein tyrosine kinase activity for NO-dependent vasorelaxation induced by stretch, isometric tension and cyclic AMP in rat pulmonary arteries

1 The NO-dependent component of cyclic AMP-induced vasorelaxation in rat pulmonary arteries is critically dependent on extracellular L-arginine but independent of endothelial cell intracellular [Ca2+]. We examined whether L-arginine uptake was also essential for NO production induced by passive stretch or isometric tension, processes also reported to be Ca2+-independent. 2 The passive length-tension curve was depressed by physiological concentrations of L-arginine (400 muM; P<0.05). Inhibition of the y(+) transporter with 10 mM L-lysine, NO synthase with L-NAME (100 <mu>M), or protein tyrosine kinase with erbstatin A (30 muM) caused identical upward shifts (P<0.001), alone or in combination. Tyrphostin 23 was similar to erbstatin A. whilst the inactive analogue tyrphostin Al and genistein were without effect. 3 L-arginine (400 <mu>M) shifted the PGF(2 alpha) concentration-response curve under isometric conditions to the right (P<0.05), whereas L-NAME or L-lysine caused a leftward shift (P<0.001). Tyrphostin 23 (30 muM) more than reversed the L-arginine-induced suppression of PGF(2 alpha)-induced tension: subsequent addition of L-NAME had no effect. The L-lysine-sensitive component of CPT cyclic AMP-induced vasorelaxation was abolished by erbstatin A. 4 ACh-induced vasorelaxation was similar to 80% inhibited by L-NAME, but was not affected by L-lysine or 400 muM L-arginine. Erbstatin A reduced the vasorelaxation by only similar to 25%. 5 We conclude that activation of NO production by stretch, isometric tension, or cyclic AMP in rat pulmonary arteries is critically dependent on the presence and uptake of physiological concentrations of extracellular L-arginine, and protein tyrosine kinase activity. This directly contrasts with ACh-induced vasorelaxation. which was independent of extracellular L-arginine, and relatively unaffected by tyrosine kinase inhibition.