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 pu lmonary arteries is critically dependent on extracellular L-arginine but in dependent of endothelial cell intracellular [Ca2+]. We examined whether L-a rginine uptake was also essential for NO production induced by passive stre tch or isometric tension, processes also reported to be Ca2+-independent. 2 The passive length-tension curve was depressed by physiological concentra tions of L-arginine (400 muM; P<0.05). Inhibition of the y(+) transporter w ith 10 mM L-lysine, NO synthase with L-NAME (100 <mu>M), or protein tyrosin e 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 cu rve under isometric conditions to the right (P<0.05), whereas L-NAME or L-l ysine caused a leftward shift (P<0.001). Tyrphostin 23 (30 muM) more than r eversed the L-arginine-induced suppression of PGF(2 alpha)-induced tension: subsequent addition of L-NAME had no effect. The L-lysine-sensitive compon ent of CPT cyclic AMP-induced vasorelaxation was abolished by erbstatin A. 4 ACh-induced vasorelaxation was similar to 80% inhibited by L-NAME, but wa s not affected by L-lysine or 400 muM L-arginine. Erbstatin A reduced the v asorelaxation by only similar to 25%. 5 We conclude that activation of NO production by stretch, isometric tensio n, or cyclic AMP in rat pulmonary arteries is critically dependent on the p resence and uptake of physiological concentrations of extracellular L-argin ine, 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.