백서 좌·우 심실근세포의 흥분-수축 특성과 세포 내 칼슘 조절 기전 및 트로포닌 단백의 칼슘 완충능 비교 ; Comparative analysis of excitation-contraction coupling properties including intracellular Ca2+ handling mechanisms and Ca2+ buffering by troponin proteins in the left and right ventricular myocytes from rats

학위논문(박사) -- 서울대학교대학원 : 의과대학 의과학과, 2022.2. 김성준. ; Despite distinctive functional and anatomical difference, a precise understanding of the cardiac interventricular difference in excitation-contraction (E-C) coupling mechanisms is still lacking. Here, we compared the results from the right and left cardiomyocytes (RVCM and LVCM) of rats. Whole-cell patch clamp technique, IonOptix system and fura-2 fluorimetry were used to measure electrical properties (action potential and ionic currents), single cell contractility and cytosolic Ca2+ ([Ca2+]i), respectively. Myofilament proteins were analyzed by Immunoblotting. RVCMs showed significantly shorter action potential duration (APD) and higher density of transient outward K+ current (Ito). However, the triggered [Ca2+]i change (Ca2+ transient) was not different, while the decay rate of the Ca2+ transient was slower in RVCM. Although the relaxation speed was also slower, the sarcomere shortening amplitude (ΔSL) was smaller in RVCM. The SERCA activity was approximately 60% lower in RVCM, partly responsible for the slower decay of the Ca2+ transient. Immunoblot analysis revealed lower expression of the cardiac troponin complex (cTn) in RVCM, implying a smaller Ca2+ buffering capacity (κS ), which was proved by in situ analysis. The introduction of the newly found 0.65-fold cTn along with the 1.31-fold Ito and 0.40-fold SERCA into a mathematical model of rat LVCM reproduced the similar Ca2+ transient, slower Ca2+ decay, shorter APD and smaller ΔSL of RVCM. Taken together, we first show the lower expression of cTn proteins in the RVCMs, which gives a clue to explain the interventricular difference in the E-C coupling kinetics. ; 심장의 좌·우심실은 구조적, 기능적으로 서로 다른 특성을 보인다. 우심실은 좌 심실에 비해 낮은 압력에 노출되어 있으며, 심실 내 압력이 빠르게 증가하여 폐동 맥보다 높아진다. 이로 인해 혈역학적 차이를 보이며 압력-용적 곡선 상 좌심실과 상이하다. 하지만 심실을 구성하는 세포인 좌·우심근세포의 생리적 특성에 대한 연 구는 부족하며, 특히 두 심근세포의 흥분-수축 연결 이론 관점의 차이는 알려진 것이 거의 없다. 본 연구에서는 백서의 좌·우심실을 구분하여 그 심근세포를 분리 한 뒤, 흥분-수축 연결의 각 단계의 생리 현상을 기록하고 비교 연구 하였다. 우심근세포의 생리 특성을 면밀히 연구하기 위해 흥분-수축 연결의 첫 ...