Arteriolar smooth muscle Ca2+ dynamics during blood flow control in hamster cheek pouch.
Intracellular calcium concentration ([Ca2+]i) governs the contractile status of arteriolar smooth muscle cells (SMC). Although studied in vitro, little is known of SMC [Ca2+]i dynamics during the local control of blood flow. We tested the hypothesis that the rise and fall of SMC [Ca2+]i underlies arteriolar constriction and dilation in vivo. Aparenchymal segments of second-order arterioles (diameter 35 +/- 2 microm) were prepared in the superfused cheek pouch of anesthetized hamsters (n = 18) and perifused with the ratiometric dye fura PE-3 (AM) to load SMC (1 microM, 20 min). Resting SMC [Ca2+]i was 406 +/- 37 nM. Elevating superfusate O2 from 0 to 21% produced constriction (11 +/- 2 microm) that was unaffected by dye loading; [Ca2+]i increased by 108 +/- 53 nM (n = 6, P < 0.05). Cycling of [Ca2+]i during vasomotion (amplitude, 150 +/- 53 nM; n = 4) preceded corresponding diameter changes (7 +/- 1 microm) by approximately 2 s. Microiontophoresis (1 microm pipette tip; 1 microA, 1 s) of phenylephrine (PE) transiently increased [Ca2+]i by 479 +/- 64 nM (n = 8, P < 0.05) with constriction (26 +/- 3 microm). Flushing blood from the lumen with saline increased fluorescence at 510 nm by approximately 45% during excitation at both 340 and 380 nm with no difference in resting [Ca2+]i, diameter or respective responses to PE (n = 7). Acetylcholine microiontophoresis (1 microA, 1 s) transiently reduced resting SMC [Ca2+]i by 131 +/- 21 nM (n = 6, P < 0.05) with vasodilation (17 +/- 1 microm). Superfusion of sodium nitroprusside (10 microM) transiently reduced SMC [Ca2+]i by 124 +/- 18 nM (n = 6, P < 0.05), whereas dilation (23 +/- 5 microm) was sustained. Resolution of arteriolar SMC [Ca2+]i in vivo discriminates key signaling events that govern the local control of tissue blood flow.
Brekke
Johan Fredrik
JF
The John B. Pierce Laboratory and Department of Cellular and Molecular Physiology, Yale University School of Medicine, 290 Congress Ave., New Haven, Connecticut 06519, USA.
Jackson
William F
WF
Segal
Steven S
SS
D000818:Animals; D001160:Arterioles / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002610:Cheek; D006224:Cricetinae; D016257:Fura-2 / Q000031:analogs & derivatives; D008297:Male; D008647:Mesocricetus; D008833:Microcirculation / Q000502:physiology; D008856:Microscopy, Fluorescence / Q000379:methods; D009061:Mouth Mucosa / Q000098:blood supply* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000098:blood supply / Q000294:innervation / Q000378:metabolism*; D010100:Oxygen / Q000032:analysis; D010783:Photometry / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology; D014666:Vasomotor System / Q000502:physiology
C098106:fura-PE3; D010100:Oxygen; D002118:Calcium; D016257:Fura-2