BIOCHEMICAL CHANGES IN HEARTS OF HYPERTENSIVE RATS FOLLOWING DIETARY PROTEINS

分离cAMP依赖性蛋白激酶同工酶（I型和II型 从10个月大的心脏组织的可溶性部分 自发性高血压大鼠（SHR），已维持9 四种实验饮食之一：低蛋白（LP）（19%蛋白质）， 标准（STD）（24%蛋白质）、高蛋白（HP）（32%蛋白质）或 蛋氨酸（1.9%蛋氨酸）（MET）通过DEAE-纤维素色谱法。 的 测定这些同工酶的活性和/或水平，以检查 饮食对心肌酶磷酸化的影响 调节蛋白 在cAMP的存在下，I型 与对照组相比，LP饮食组的蛋白激酶减少了3倍和4倍。 32%和蛋氨酸组SHR。 II型蛋白 来自所有四个饮食组的激酶显示出相似的活性， cAMP的存在和不存在。 而心脏中的cAMP结合活性 来自STD、HP和MET组大鼠的组分与蛋白激酶相关 活性，来自LP的心脏组分中的cAMP结合活性 对照组大鼠酶活性高于对照组。 在 受磷蛋白（肌浆网（SR）蛋白，其磷酸化 调节由[Ca2 +-Mg2 +]-ATP酶）磷酸化介导的CA 2+转运 研究表明，加入cAMP显著刺激受磷蛋白 磷酸化，但刺激的程度是 MET组动物最高，LP组最低， 显著 Ⅰ型同工酶活性的降低， 低蛋白饮食的SHR的心脏分数可能是由于 酶对cAMP的反应或酶数量的减少 分子。 这种情况可能会影响磷酸化的程度， 心脏调节蛋白，从而损害心脏生理学， 高血压

cAMP-dependent protein kinase isozymes (Type I and Type II) were isolated from the soluble fractions of cardiac tissue from 10-month-old spontaneously hypertensive rats (SHR) which had been maintained for nine months on one of four experimental diets: low protein (LP) (19% protein), standard (STD) (24% protein), high protein (HP) (32% protein) or high methionine (1.9% methionine) (MET) by DEAE-cellulose chromatography. The activity and/or levels of these isozymes were determined to examine the influence of diet on the enzyme's effect on the phosphorylation of cardiac regulatory proteins. In the presence of cAMP the activity of the Type I protein kinase was reduced by 3 and 4-fold in the LP diet group compared to the SHR on 32% and methionine diet groups respectively. Type II protein kinase from all four diet groups exhibited similar activities in the presence and absence of cAMP. While cAMP-binding activities in the cardiac fractions from STD, HP and MET groups of rats correlate to protein kinase activities, cAMP-binding activities in the cardiac fractions from the LP group of rats by contrast were higher than enzyme activities. In the phospholamban (sarcoplasmic reticulum (SR) protein whose phosphorylation regulates CA2+ transport mediated by [Ca2+-Mg2+]-ATPase) phosphorylation study, addition of cAMP significantly stimulated phospholamban phosphorylation in all diet groups but the extent of stimulation was highest in the MET group of animals and lowest in the LP groups was not significant. The decrease in the activity of Type I isozyme found in the cardiac fractions from SHR fed low protein diet may be due to a defect in response of the enzyme to cAMP or a reduction in the number of enzyme molecules. Such a condition may affect the degree of phosphorylation of cardiac regulatory proteins, thus impairing cardiac physiology in hypertension.