Role of endothelial factors in active hyperemic responses in contracting canine muscle.
We investigated whether endothelium-derived relaxing factor (EDRF) and prostaglandins, which may be released under conditions of increased blood flow, contribute to the active hyperemia in contracting muscle of anesthetized dogs. The venous outflow from the left gastrocnemius muscle was isolated and measured. The tendon was cut and placed in a force transducer. One group served as a control (Con; n = 9); EDRF synthesis was inhibited using N omega-nitro-L-arginine methyl ester (L-NAME) in a second group (n = 9), and a third group (n = 7) received L-NAME and indomethacin (L-NAME+Indo) to inhibit prostaglandin synthesis. After resting measurements, the distal end of the cut sciatic nerve was stimulated to produce isometric contractions at 1, 2, 4, and 6 twitches/s for 6-8 min, separated by 25-min recovery periods. Blood flow and O2 uptake increased linearly from resting values of 11.8 +/- 2.4 and 0.3 +/- 0.05 ml.100 g-1.min-1, respectively, to maximal values of 84.2 +/- 5.1 and 11.1 +/- 0.7 ml.100 g-1.min-1 in the Con group; neither these values nor those for tension development were different from values observed at comparable contraction frequencies in the L-NAME and L-NAME+Indo groups. At rest, resistance was greater (P < 0.05) in both the L-NAME and L-NAME+Indo groups compared with Con, the highest value (P < 0.05) occurring in the L-NAME+Indo group. Muscle resistance decreased (P < 0.05) in all groups at all contraction frequencies; the values were not different among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)
King-Vanvlack
C E
CE
School of Rehabilitation Therapy, Queen's University, Kingston, Ontario, Canada.
Curtis
S E
SE
Mewburn
J D
JD
Cain
S M
SM
Chapler
C K
CK
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D004285:Dogs; D004730:Endothelium, Vascular / Q000503:physiopathology*; D006614:Hindlimb; D006940:Hyperemia / Q000503:physiopathology*; D007213:Indomethacin / Q000494:pharmacology; D007537:Isometric Contraction; D009132:Muscles / Q000098:blood supply*; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D010101:Oxygen Consumption / Q000187:drug effects; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D011448:Prostaglandin Antagonists; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin