Measurement of intracellular Ca2+ concentration changes by use of fura-2 in the generation of myogenic contraction of dog cerebral artery in response to quick stretch.
In the present study, by using fura-2, we attempted to measure the changes of intracellular free Ca2+ concentrations ([Ca2+]i) in the generation of myogenic contraction of dog cerebral artery in response to quick stretch. Quick stretch was applied to rubber sheets or dog cerebral arteries at a rate of 10 cm/sec for 30 sec with the amount of stretch equivalent to 40% of the initial length of materials. In rubber sheets and fura-2-unloaded cerebral arteries, the intensities of 500 nm fluorescence due to excitation at 340 nm (F340) and 380 nm (F380) were reduced by quick stretch although the ratio signal (F340/F380:R340/380) was not appreciably affected. F340, F380, and R340/380 remained unchanged for 30 sec of the stretch period. By contrast, in fura-2-loaded cerebral artery segments, before the appearance of delayed contraction in response to quick stretch, R340/380 was enormously raised by the mechanical stimulation. The stretch-induced myogenic contraction and the corresponding change in R340/380 were abolished by repeated stretches of the artery segments in Ca(2+)-free medium containing 0.2 mM EGTA or in the presence of papaverine (10(-4) M). L-type Ca2+ channel antagonists (nicardipine and d-cis-diltiazem) inhibited both [Ca2+]i and mechanical activity of the cerebral arteries in response to stretch in a concentration-dependent and parallel manner. These findings indicate that changes of R340/380 in the generation of myogenic contraction of fura-2-loaded dog cerebral artery in response to quick stretch reflect those of [Ca2+]i in the response. Fura-2 seems to be a useful Ca2+ indicator to measure the Ca2+ mobilization of vascular smooth muscle in response to quick stretch at the whole tissue level.
Tanaka
Y
Y
Department of Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Nakayama
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002536:Cerebral Arteries / Q000378:metabolism* / Q000502:physiology; D004110:Diltiazem / Q000494:pharmacology; D004285:Dogs; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism*; D016257:Fura-2 / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000502:physiology; D009529:Nicardipine / Q000494:pharmacology; D012026:Reflex, Stretch / Q000187:drug effects / Q000502:physiology*; D013314:Stress, Mechanical
D002121:Calcium Channel Blockers; D005456:Fluorescent Dyes; D009529:Nicardipine; D004110:Diltiazem; D002118:Calcium; D016257:Fura-2