title: Arteriolar smooth muscle Ca2+ dynamics during blood flow control in hamster cheek pouch.
abstract: 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.
authors.affiliation: 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.
authors.forename: Johan Fredrik
authors.initials: JF
authors.lastname: Brekke
authors.forename: William F
authors.initials: WF
authors.lastname: Jackson
authors.forename: Steven S
authors.initials: SS
authors.lastname: Segal
mesh_terms: 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
chemical_list: C098106:fura-PE3; D010100:Oxygen; D002118:Calcium; D016257:Fura-2