アブストラクト(24巻3号:神奈川歯学)

神奈川歯学

Japanese

Title : 咬筋小胞体の定常状態Calcium LoadにおけるCalcium Permeabilityの性格
Subtitle : 原著
Authors : 高田晴彦, 伊藤春生
Authors(kana) :
Organization : 神奈川歯科大学歯科薬理学教室
Journal : 神奈川歯学
Volume : 24
Number : 3
Page : 440-449
Year/Month : 1989 / 12
Article : 原著
Publisher : 神奈川歯科大学学会
Abstract : 「緒言」外液ATPを非加水分解性ATP誘導体(β, γ-methylene ATP)と置換した場合, 骨格筋から単離された筋小胞体(SR)内腔Ca量がSR外側に結合しているCaレベルにまで減少すること, そして, Ca2+ ionophoreによってSRからの急速なCa2+ 遊離が生ずること, などから, SRはATP存在下でその加水分解に共役した活発なCa2+ 能動輸送を行なっていることが明らかとなった. 一方, SR内腔でCa2+ と結合することによってCa2+ 輸送を増強するoxalateの非存在下では, SRのCa2+ uptakeの定常状態(steady-state)を得ることが可能であるが, この定常状態Ca2+ uptakeは, 温度, pH, Mg2+, nucleotide, あるいは外液Ca2+ 濃度, などで変化する. これは, SRに存在する複数以上のCa2+ flux経路が影響を受けた結果である.
Practice : 歯科学
Keywords : 咬筋小胞体, 興奮-収縮連関, Ca2+ permeability, Ca2+ load, Ca2+ gradient

English

Title : Characterization of Calcium Permeability at Steady-State Calcium Load in Masseter Muscle Sarcoplasmic Reticulum
Subtitle : Original article
Authors : Haruhiko TAKADA, Haruo Ito
Authors(kana) :
Organization : Department of Pharmacology, Kanagawa Dental College
Journal : Kanagawa Shigaku
Volume : 24
Number : 3
Page : 440-449
Year/Month : 1989 / 12
Article : Original article
Publisher : Kanagawa Odontological Society
Abstract : Abstract : To characterize the route of calcium permeability, the effect of intravesicular and extravesicular calcium concentration on the permeability from sarcoplasmic reticulum (SR) vesicles isolated from canine masseter muscle was determined by measuring net efflux of calcium after stopping pump-mediated fluxes. The apparent permeability, calculated as the net efflux divided by the total intravesicular calcium, depended on calcium load. When the intravesicular bound calcium was taken into accunnt, net calcium efflux was found to be linearly related to the difference in calcium concentration across the SR membrane. The first order rate constant of calcium permeability was nearly identical when efflux was initiated by the addition of EGTA or glucose plus hexokinase to quench calcium pump by lowering activator calcium or by converting substrate ATP to ADP and glucose 6-phosphate, respcetively. Extravesicular calcium concentration between 0.001μM and 33.9μM had no great effect on calcium permeabillty. The results suggest that some minimal calcium gradient may be required in order to observe a substantial passive calcium efflux, and the passive calcium efflux is not carrier mediated. It is also postulated that passive route of efflux during calcium accumulation is relatively small and that physiological calcium release during excitation-contraction coupling does not occur through this route.
Practice : Dentistry
Keywords : Ca2+ permeability, Ca2+ load, Ca2+ gradient