Mechanism of contraction induced by bradykinin in the rabbit saphenous vein.
1. By using fura-PE3 fluorometry and receptor-coupled permeabilization by alpha-toxin, the mechanism of the bradykinin (BK)-induced contraction was determined in the rabbit saphenous vein (RSV). The receptor subtype responsible for the BK-induced contraction of RSV was determined by means of a pharmacological blocker study and reverse transcription polymerase chain reaction (RT-PCR). 2. In the presence of extracellular Ca2+ (1.25 mM), BK (10(-11)-3 x 10(-7) M) induced increases in both the cytosolic Ca2+ concentration ([Ca2+]i) and force, in a concentration-dependent manner. Both the release of Ca2+ from the store site and the influx of extracellular Ca2+ contribute to an increase in [Ca2+]i induced by BK. 3. In the absence of extracellular Ca2+, the application of 10(-7) M BK induced transient elevations of [Ca2+]i and force, both of which thereafter declined to the levels observed before the application of BK. When extracellular Ca2+ was replenished (1.25 mM), [Ca2+]i and force increased to form a peak, followed by a sustained elevation in the presence of BK. When an RSV strip was pretreated with 10(-5) M thapsigargin for 20 min, the BK-induced transient increases in both [Ca2+]i and force were markedly inhibited. 4. These responses induced by BK were inhibited by Hoe 140 (D-Arg-[Hyp3, Thi5, D-Tic7, Oic8] bradykinin), a highly specific bradykinin B2 receptor antagonist, in a concentration-dependent manner. In RT-PCR, B2-receptor mRNA was expressed in the smooth muscle of RSV. 5. The [Ca2+]i-force relationships, which were determined by cumulative applications of extracellular Ca2+ (0-5 mM) during 118 mM K(+)-depolarization, shifted to the upper left in the presence of BK, thus indicating that BK induced a greater force than 118 mM K(+)-depolarization for a given level of [Ca2+]i. 6. In alpha-toxin-permeabilized preparations of RSV, application of 10(-7) M BK after a steady state contraction had been induced by a mixture of 5 x 10(-7) M Ca2+, 10(-6) M GTP and 10(-6) M captopril caused an additional force development at a constant [Ca2+]i. However, treatment with 1 mM guanosine-5'-O-(beta-thiodiphosphate) (GDP beta S) for 5 min before and during the application of BK (10(-7) M), abolished this BK-induced additional contraction. 7. These results indicated that in RSV: (1) BK elicits vasoconstriction by increasing the Ca2+ influx from the extracellular space, Ca2+ release from intracellular thapsigargin-sensitive storage sites and increasing the Ca2+ sensitivity of the contractile apparatus, (2) the BK-induced increase in Ca2+ sensitivity is mediated by G-protein, (3) the BK-induced contractions are mediated via B2-receptors and (4) the smooth muscle cells express B2-receptor mRNA.
Eguchi
D
D
Division of Molecular Cardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Nishimura
J
J
Kobayashi
S
S
Komori
K
K
Sugimachi
K
K
Kanaide
H
H
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D018002:Receptors, Bradykinin / Q000096:biosynthesis / Q000187:drug effects; D012501:Saphenous Vein / Q000187:drug effects*; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000494:pharmacology
D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D012333:RNA, Messenger; D018002:Receptors, Bradykinin; C098106:fura-PE3; D019284:Thapsigargin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2