Role of Ca++ gradient in functional dilatation in the microvessels of rat skeletal muscle.
During skeletal muscle contraction functional dilatation (FD) is a well established phenomenon, which is usually linked to the accumulation of various vasodilator metabolites. The present study aimed to establish the role of calcium ions (Ca++) in the functional dilatation of skeletal muscle microvessels especially during single & few twitches. The FD was studied in urethane anaesthetized rats whose spinotrapezius muscle was prepared for intravital microscopy. After stimulating the muscle with few twitch (1 & 3 Hz) and tetanic frequency (40 Hz), muscle contracted and showed dilatation. However the dilator response was quickest (1 Hz : 10 +/- 0.40, 3 Hz : 02 +/- 0.47 sec and 40 Hz : 02 +/- 0.10 sec) and maximum in magnitude (1 Hz : 25 +/- 0.30%, 3 Hz : 35 +/- 0.49% and 40 Hz : 55 +/- 0.39%) in terminal arteriole and with tetanic frequency. Calcium channel blockade by Diltiazem abolished the FD response except for tetanic stimulation contraction. Findings suggested possible involvement of Ca++ movement in functional dilatation which was initiated by passive efflux of Ca++ from smooth muscle of vessel and then maintained during higher frequency stimulation by release of local metabolities.
Mittal
Sunita
S
Department of Physiology, Himalayan Institute of Medical Sciences, Jolly Grant, Dehradun 248 140. sunitasanjeevmittal@yahoo.co.in
Tandon
Harish Chandra
HC
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D008297:Male; D008833:Microcirculation / Q000378:metabolism; D009126:Muscle Relaxation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002118:Calcium