缺氧对右心室最大心肌血流量的影响

为了探讨缺氧对冠状血管贮备力的影响,我们观察了缺氧时大鼠血流动力学及右心室最大心肌血流量的变化。结果表明,急性缺氧引起ＰａＯ２、心输出量及氧运送量降低,但右心室心肌血流量增加,右心室最大与安静血流量比值降低。慢性缺氧时ＰａＯ２降低,血球比积和右心室重量指数增加,氧运送量和右心室血流量正常,但最大血流量降低,小动脉增厚、外膜胶元增加。以上结果提示,慢性缺氧对冠状血管贮备减少可能是小动脉壁增厚、外膜胶元增加和血液粘滞性增加及右心室肥大的结果。     

Effects of Blockade of Hyperpolarization-Activated Ion Currents (I h) on Autonomic Control of the Heart in Rats: Age-Related Peculiarities

In our experiments, we studied the effects of intravenous introduction of ZD7288, a selective blocker of the currents activated by hyperpolarization (I _h), on the cardial activity of 1- and 3-week-old and young adult (20-week-old) rats. Introduction of the blocker caused a dose-dependent decrease in the heart rate (HR) in all age groups. A maximum and a minimum expression of bradycardia were observed in 1- and 3-week-old rats, respectively. Stimulation of the n. vagus against the background of bradycardia that developed after the blockade of I _h led to a further drop in the HR. In this case, the expression of the effect of stimulation of the n. vagus depended on the dose of the introduced blocker. The blockade of I _h influenced the cardial reaction to introduction of an agonist of -adrenoreceptors, isoproterenol, in rats of early age and young adult rats, but not in 3-week-old rats. Therefore, the blockade of I _h changes the reaction of the heart on sympathetic and parasympathetic regulatory influences, and the expression of these changes significantly depends on the animal's age. This allows us to conclude that not only the pacemaker activity of cardiomyocytes per se but also autonomic modulation of the cardial activity demonstrate a significant dependence on the function of hyperpolarization-activated ionic channels; this function is characterized by substantial age-related peculiarities.