Function and energetic state of isolated hearts of rats with spontaneous hypertension

The goal of this work was to compare response of pump function and energy m etabolism of isolated hearts of male rats with spontaneous hypertension (SH R) at age of 12 weeks (blood pressure 170+/-5 mmHg) and normotensive WKY ra ts of the same age and sex (blood pressure 115+/-5 mmHg) to volume and resi stance loads. The SHR hearts were significantly hypertrophied - dry heart/b ody weight ratio was elevated by 48%. At standard perfusion conditions the aortic output of SHR hearts was significantly higher (by 51%) while other p arameters of cardiac function differed insignificantly. During volume load induced by increase of atrial filling pressure from 5 to 30 cm H2O maximal cardiac output and maximal aortic output of SHR hearts were 39% and 36%, re spectively, higher than those of WKY rats. During resistance load induced b y elevation of aortic pressure from 60 to 110 cm H2O, the cardiac output of SHR hearts was preserved on significantly higher level as compared with WK Y rats; and at complete aortic clamping maximal cardiac work was 68% higher in SHR vs. WKY rats. Thus the advantage of the hypertrophied heart was man ifested more clearly at higher resistance than volume load. However, when f unctional parameters were related to dry heart weight all differences becam e insignificant, what allowed to consider myocardial contractility normal. The measurement of myocardial content of high energy phosphates performed b oth before and after functional loading showed a tendency to decreased leve ls of ATP and phosphocreatine in SHR hearts. However, only ATP/ADP ratio an d total creatine level were significantly (by 10-13%) lower. The correlatio n of contractile indices with content of high energy phosphates inherent to the control group was not observed in SHR group. The results evidence that hearts of SHR are better adapted to elevated loads than hearts of WKY rats , however, this advantage is associated with disturbed interrelation betwee n myocardial energy state and its function.