Influence of nitric oxide on vascular resistance and muscle mechanics during tetanic contractions in situ.
Studies of the effect of nitric oxide (NO) synthesis inhibition were performed in the isometrically contracting blood-perfused canine gastrocnemius-plantaris muscle group. Muscle blood flow (Q) was controlled with a pump during continuous NO blockade produced with either 1 mM L-argininosuccinic acid (L-ArgSA) or N(G)-nitro-L-arginine methyl ester (L-NAME) during repetitive tetanic contractions (50-Hz trains, 200-ms duration, 1/s). Pump Q was set to match maximal spontaneous Q (1.3-1.4 ml. min(-1). g(-1)) measured in prior, brief (3-5 min) control contraction trials in each muscle. Active tension and oxygen uptake were 500-600 g/g and 200-230 microl. min(-1). g(-1), respectively, under these conditions. Within 3 min of L-ArgSA infusion, vascular resistance across the muscle (R(v)) increased significantly (from approximately 100 to 300 peripheral resistance units; P < 0.05), whereas R(v) increased to a lesser extent with L-NAME (from approximately 100 to 175 peripheral resistance units; P < 0.05). The increase in R(v) with L-ArgSA was unchanged by simultaneous infusion of 0.5-10 mM L-arginine but was reduced with 1-3 microg/ml sodium nitroprusside (41-54%). The increase in R(v) with L-NAME was reversed with 1 mM of L-arginine. Increased fatigue occurred with infusion of L-ArgSA; active tension and intramuscular pressure decreased by 62 and 66%, whereas passive tension and baseline intramuscular pressure increased by 80 and 30%, respectively. These data indicate a possible role for NO in the control of R(v) and contractility within the canine gastrocnemius-plantaris muscle during repetitive tetanic contractions.
Ameredes
B T
BT
Department of Cell Biology and Physiology, and Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA. ameredes@pop.pitt.edu
Provenzano
M A
MA
D000818:Animals; D001125:Argininosuccinic Acid / Q000494:pharmacology; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009599:Nitroprusside / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology*
D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D001125:Argininosuccinic Acid; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester