FURUKAWA SATOSHI; KIMURA HIROKO; MUKAIDA MASAHIRO; YAMAKURA FUMIYUKI; KONO HIROSHI; IKEDA KEIICHI
順天堂医学 2008/09 順天堂大学
Objective : We investigated the effects of exercise training starting after emergence ofhypertension (15-week old) on nitrative stress and protein levels and activities of nitrative stress-related enzymes in the hearts of spontaneously hypertensive rats (SHR). Material and Methods I We examined the hearts of 25-week old (wk) SHR that performed either 10 wk of voluntary exercise training (Ex) or remained intact (Cont). We also analyzed 5 wk and 15 wk SHR in order to determine basal alterations of nitrative stress and enzymes. Starting at 15 weeks old, 25 wk Ex SHR exercised by voluntary running in a wheel-cage for 10 weeks. At the end of the breeding or training period, rats were anesthetized and hearts were collected. We measured the level of nitrotyrosine by the time-resolved fluoroimmunoassay method, the amount of manganese-containing (Mn-) and copper/zinc-containing (Cu, Zn-) superoxide dismutase (SOD), and endothelial nitric oxide synthase (eNOS) in the heartby the western blotting method. Furthermore Mn- and Cu, Zn-SOD and total NOS activity were measured by the spectrometry method. Result : Systolic blood pressure was elevated at 15 wk and remained high until 25 wk Cont SHR. Exercise did not affect the blood pressure. Although there was no significant increase in 3-nitrotyrosine (3-NT) concentration in 100,000 g precipitate fractions (P2) of heart homogenate of 15wk SHR, a significant increase in 3-NT concentration was observed in that of 25 wk Cont SHR. This increase in 3-NT concentration was significantly attenuated in that of 25 wk Ex SHR. The same alterations of 3-NT levels were observed by immunohistochemical analysis using specific antibody for 3-NT. Protein levels of endothelial nitric oxide synthase (eNOS) in the membrane fractions were reduced in 15wk and 25wk Cont SHR compared with those of 5 wk SHR, but not affected by Ex. This evidence was supported by the measurements of total NOS activity in the same fractions. Protein levels of Cu, Zn-SOD were reduced to a greater degree in 25wk Ex and Cont SHR than in those of 5wk and 15wk SHR, but there was no significant effect observed by Ex. The same results were obtained upon measurement of Cu, Zn-SOD activity. However, protein of Mn-SOD increased significantly in 15 wk SHR, compared to that of 5 wk SHR. Although there was no significant difference in Mn-SOD levels between 25 wk Cont SHR and 15 wk SHR, significant increases in Mn-SOD levels and activity were observed in 25 wk Ex SHR, compared with those of 25 wk Cont SHR. This evidence accounts for the significant attenuation of 3-NT formation in the P2 fraction of 25 wk Ex SHR. Conclusion : We conclude that 10 weeks of exercise training after the emergence of hypertension could reduce nitrative stress in the organelle fractions of the heart as a result of the increase in Mn-SOD.