Effects of α1-Adrenergic Receptor Stimulation on Intracellular Na+ Activity and Twitch Force in Guinea-Pig Ventricular Muscles

• 영문명: Effects of α₁-Adrenergic Receptor Stimulation on Intracellular Na⁺ Activity and Twitch Force in Guinea-Pig Ventricular Muscles
• 발행기관: 대한생리학회
• 저자명: Chae, Soo-Wan Gong, Q.Y. Wang, D.Y. Lee, Chin-O.
• 간행물 정보: 『대한생리학회지』제29권 제2호, 203~216쪽, 전체 14쪽
• 주제분류: 의약학 > 의학일반
• 파일형태: PDF
• 발행일자: 1995.12.31

영문 초록

The effects of α₁-adrenergic receptor stimulation on membrane potential, intracellular Na⁺ activity, and twitch force were investigated in ventricular muscles from guinea-pig hearts. Action potentials, intracellular Na⁺ activity, and twitch force of ventricular papillary muscles were measured simultaneously under various experimental conditions. Stimulation of the α₁-adrenergic receptor by phenylephrine produced variable changes in action potential duration, a slight hyperpolarization of the diastolic membrane potential, a decrease in intracellular Na⁺ activity, and a biphasic inotropic response in which a transient negative inotropic response was followed by a sustained positive inotropic response. These changes were blocked by prazosin, an antagonist of the α₁-adrenergic receptor, but not by atenolol, an antagonist of the β-adrenergic receptor. This indicates that the changes in membrane potential, intracellular Na⁺ activity, and twitch force are mediated by stimulation of the α₁-adrenergic receptor, but not by stimulation of β-adrenergic receptor. The decrease in intracellular Na⁺ activity was not observed in quiescent muscles, depending on the rate of the action pontentials in beating muscles. The intracellular Na⁺ activity decrease was substantially inhibited by tetrodotoxin. However, the decrease in intracellular Na⁺ activity was not affected by an inhibition of the Na⁺-K⁺ pump. Therefore, the decrease in intracellular Na⁺ activity mediated by the α₁-adrenergic receptor appears to be due to a reduction of Na⁺ influx during the action potential, perhaps through tetrodotoxin sensitive Na⁺ channels. Our study also revealed that the decrease in intracellular Na⁺ activity might be related to the transient negative inotropic response. The intracellular Na⁺ activity decrease could lower intracellular Ca²⁺ through the Na⁺-Ca²⁺ exchanger and thereby produce a decline in twitch force.

키워드

Guinea-pig ventricle α₁-adrenergic receptor, Intracellular Na⁺ activity Membrane potential Twitch force Biphasic inotropic response Phenylephrine Prazosin