Studies on the developmental and species difference of cardiac function : analysis of pharmacological and physiological specificity of mouse myocardia

主要研究结果如下：1）研究了成年小鼠心室肌对α-肾上腺素能刺激的负性变力反应的机制。结果提示：（1）α-肾上腺素能受体刺激成年小鼠心室肌可引起持续的负性变力反应，其机制可能是通过增加Na+/Ca ~（2+）交换器的Ca ~（2+）流出而实现的。（2）α-肾上腺素能受体刺激成年小鼠心肌可引起上述负性变力反应，而对新生小鼠心肌可产生正性变力反应。在内皮素I和血管紧张素II中观察到类似的变力性发育转换;这些药物在新生儿中产生阳性反应，但在成人中为阴性。3）在小鼠左心房中，乙酰胆碱产生双相变力性反应，即，收缩力的短暂下降，随后是后期的增加。发现阳性反应是由心内膜内皮释放的前列腺素介导的。

Research results are summarized as follows.1) Mechanisms underlying the negative inotropic response to alpha-adrenergic stimulation in adult mouse ventricular myocardium were studied. Results obtained in the present study suggest that the sutained negative inotropic response to alpha-adrenoceptor stimulation of adult mouse ventricular myocardium is mediated by enhancement of Ca2+ efflux through the Na+/Ca2+ exchanger.2) Alpha-adrenergic stimulation results in a negative inotropic response in adult mouse myocardia as described above, while it produces positive inotropism in neonatal myocardia. Similar developmental conversion of inotropism was observed with endothelin I and angiotensin II ; these agents produced positive response in the neonate but negative in the adult.3) In mouse left atria, acetylcholine produced a biphasic inotropic response, i.e., a transient decrease in contractile force followed by a late increase. The positive response was found to be mediated by prostaglandin released from the endocardial endothelium.