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 avera ge amounts of mitochondria (Mit) and sarcoplasmic reticulum (SR) prote ins isolated from the ventricle of SHRsp were 37% and 25% greater, res pectively, when compared with those of WKY. Mit cytochrome c oxidase a ctivities (mu mol/min/mg) were 4.63 +/- 0.71 for SHRsp and 5.55 +/- 0. 50 for WKY myocardium (($) over bar x +/- s), so that the activity of the former was significantly reduced by 17% (P<0.01). Mit Ca2+, Mg2+-A TPase activity (mu mol/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 hyper tensive rats was not different from that in control rats. The spectra of intrinsic protein fluorescence in 300-380 mm at an excitation wavel ength of 290 nm were also identical in the Mit or SR between SHRsp and WKY myocardium. An ultrastructural analysis showed that there were mo re new-born Mit with smaller volumes and an increased number of isolat ed Mit in vitro from SHRsp myocardium, while there were larger Mit vol umes isolated from WKY myocardium. These results demonstrated the diso rder of mitochondrial energy metabolism in hypertrophied myocardium fr om SHRsp, which may be involved in the abnormality of myocardial calci um metabolism.