Abaurre P F, Vassallo D V, Mill J G, Leite C M
Departamento de Ciências Fisiológicas, Universidade Federal do Espírito Santo, Vitória, Brasil.
Braz J Med Biol Res. 1988;21(5):1049-52.
Left ventricle papillary muscles from Wistar male rats were studied before, during and after urea treatment. Urea was used at a concentration (17 mM) equivalent to a plasma level of 100 mg/dl. To verify whether these effects were produced by an increase in osmolarity, the study was repeated using 17 mM saccharose. The results showed that isometric force development decreased after washing out urea from the bath but inotropic responses to isoproterenol (IPA) and increased extracellular calcium attained values similar to those obtained before urea treatment. Thus, the percentual increments due to IPA and calcium were enhanced after urea treatment. The increased osmolarity due to saccharose did not produce any change in contraction or in the responses to inotropic interventions. It is suggested that urea modifies the excitation-contraction coupling mechanism in heart muscle, reducing the force developed at the steady state control level without reducing the responses to the inotropic interventions.
对雄性Wistar大鼠的左心室乳头肌在尿素处理前、处理期间和处理后进行了研究。使用的尿素浓度（17 mM）相当于血浆水平100 mg/dl。为了验证这些效应是否由渗透压升高引起，使用17 mM蔗糖重复了该研究。结果显示，从浴槽中洗去尿素后等长力发展降低，但对异丙肾上腺素（IPA）的变力反应以及细胞外钙增加时达到的值与尿素处理前获得的值相似。因此，尿素处理后IPA和钙引起的百分比增加有所增强。蔗糖引起的渗透压升高未对收缩或变力干预反应产生任何变化。提示尿素改变了心肌的兴奋-收缩偶联机制，在不降低对变力干预反应的情况下，降低了稳态控制水平下产生的力量。
