Contributions of endothelium-derived relaxing factors to control of hindlimb blood flow in the mouse in vivo.
We determined the contributions of various endothelium-derived relaxing factors to control of basal vascular tone and endothelium-dependent vasodilation in the mouse hindlimb in vivo. Under anesthesia, catheters were placed in a carotid artery, jugular vein, and femoral artery (for local hindlimb circulation injections). Hindlimb blood flow (HBF) was measured by transit-time ultrasound flowmetry. N(omega)-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg plus 10 mg x kg(-1) x h(-1)), to block nitric oxide (NO) production, altered basal hemodynamics, increasing mean arterial pressure (30 +/- 3%) and reducing HBF (-30 +/- 12%). Basal hemodynamics were not significantly altered by indomethacin (10 mg x kg(-1) x h(-1)), charybdotoxin (ChTx, 3 x 10(-8) mol/l), apamin (2.5 x 10(-7) mol/l), or ChTx plus apamin (to block endothelium-derived hyperpolarizing factor; EDHF). Hyperemic responses to local injection of acetylcholine (2.4 microg/kg) were reproducible in vehicle-treated mice and were not significantly attenuated by L-NAME alone, indomethacin alone, L-NAME plus indomethacin with or without co-infusion of diethlyamine NONOate to restore resting NO levels, ChTx alone, or apamin alone. Hyperemic responses evoked by acetylcholine were reduced by 29 +/- 11% after combined treatment with apamin plus charybdotoxin, and the remainder was virtually abolished by additional treatment with L-NAME but not indomethacin. None of the treatments altered the hyperemic response to sodium nitroprusside (5 microg/kg). We conclude that endothelium-dependent vasodilation in the mouse hindlimb in vivo is mediated by both NO and EDHF. EDHF can fully compensate for the loss of NO, but this cannot be explained by tonic inhibition of EDHF by NO. Control of basal vasodilator tone in the mouse hindlimb is dominated by NO.
Fitzgerald
Sharyn M
SM
Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia.
Bashari
Homaira
H
Cox
Jessica A
JA
Parkington
Helena C
HC
Evans
Roger G
RG
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001685:Biological Factors / Q000378:metabolism*; D001783:Blood Flow Velocity; D001794:Blood Pressure; D018999:Charybdotoxin / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D045462:Endothelium-Dependent Relaxing Factors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006339:Heart Rate; D006614:Hindlimb; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000098:blood supply*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D001685:Biological Factors; D016861:Cyclooxygenase Inhibitors; D045462:Endothelium-Dependent Relaxing Factors; D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011453:Prostaglandins; D014665:Vasodilator Agents; C067410:endothelium-dependent hyperpolarization factor; D018999:Charybdotoxin; D009599:Nitroprusside; D001030:Apamin; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D011451:Prostaglandin-Endoperoxide Synthases; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin