THE IMPORTANCE OF BICARBONATE-BUFFER ON CARDIAC FUNCTION: Contractility, Membrane Potentials and ATP Content of Isolated Atria in the Absence of External Buffers

심장기능(心臟機能)에 미치는 Bicarbonate-Buffer의 중요성(重要性) : Buffer 제거(除去)에 의(依)한 유리심방(遊離心房)의 수축성(收縮性), 막전위(膜電位) 및 ATP 함량(含量)의 변동(變動)

The effects of omission of buffers from Krebs-Ringer medium on contractile activity, membrane potentials and ATP content of electrically stimulated isolated rat atria were investigated. 1) Contractile status: A rapid and marked depression of the contractile activity of atria occurred when buffer-free medium was substituted for the normal Krebs-Ringer medium. 2) Electrical status: The omission of buffers from medium did not alter the resting or action potential magnitudes of atria. However, the action potential duration was on initial increase followed by a decrease in the buffer-free medium. 3) ATP concentration: The omission of buffers from medium resulted in a marked decrease in the ATP levels of atria. It has been also found in the present study that bicarbonate buffer plays an important role for the maintenance of the contractility and ATP levels of the heart. The contractile depression by the omission of buffers was not directly associated with electrical alterations in resting or action potentials of the heart. In the absence of bicarbonate-buffer, glucose no longer plays to maintain the contractile activity and the ATP levels of rat atria.