Biochemical and biophysical characteristics of mitochondria in the hypertrophic hearts from hypertensive rats.

A comparative study of the biochemical and biophysical characteristics of myocardial mitochondria was conducted in 16-weeks-old male stroke-prone spontaneously hypertensive rats (SHRsp) and normotensive Wistar-Kyoto control rats (WKY) (n = 6-12). Cardiac and ventricular weights of SHRsp were significantly higher than those of the WKY group. The average amounts of mitochondria (Mit) and sarcoplasmic reticulum (SR) proteins isolated from the ventricle of SHRsp were 37% and 25% greater, respectively, when compared with those of WKY. Mit cytochrome c oxidase activities (mumol/min/mg) were 4.63 +/- 0.71 for SHRsp and 5.55 +/- 0.50 for WKY myocardium (mean +/- s), so that the activity of the former was significantly reduced by 17% (P < 0.01). Mit Ca2+, Mg(2+)-ATPase activity (mumol/min/mg) of SHRsp was 24% lower than that of WKY myocardium (P < 0.01). The fluorescence polarization of myocardial Mit membrane labelled with DPH (1, 6-diphenyl-1, 3, 5-hexatriene) in hypertensive rats was not different from that in control rats. The spectra of intrinsic protein fluorescence in 300-380 nm at an excitation wavelength of 290 nm were also identical in the Mit or SR between SHRsp and WKY myocardium. An ultrastructural analysis showed that there were more new-born Mit with smaller volumes and an increased number of isolated Mit in vitro from SHRsp myocardium, while there were larger Mit volumes isolated from WKY myocardium. These results demonstrated the disorder of mitochondrial energy metabolism in hypertrophied myocardium from SHRsp, which may be involved in the abnormality of myocardial calcium metabolism.