Discoloration characteristics of 3 major muscles (LD, Longissimus dorsi; PM, Psoas major; SM, Semimemebranosus) from Korean native cattle (Hanwoo) were monitored during 7 d of cold storage at 4• C. The muscles were obtained from 12 Hanwoo carcasses at 24 h postmortem. Meat color (CIE L*, a*, b*), myoglobin (Mb) concentration, chemical form, metmyoglobin (MetMb) reducing ability (MRA), mitochondria concentration, and thiobarbituric acid reactive substance (TBARS) were measured at 1, 3, 5, and 7 d of storage. Although there were no significant differences in CIE a* and b*-values between the 3 muscles at day 1, the values of PM muscle were significantly (P < 0 .05) lower than those of LD and SM muscles at day 5 and 7. PM muscle showed a rapid decrease in the oxymyoglobin (OxyMb) and an increase in MetMb, which resulted in a significantly (P < 0.05) higher percentage of MetMb in PM muscle compared to LD and SM muscles. Also, the Mb and mitochondria concentration of PM muscle was significantly (P < 0.05) higher than those of LD and SM muscles. However, there were no significant differences in MRA, pH, or TBARS between the 3 muscles during 7 d of cold storage. It was concluded that rapid discoloration (that is, MetMb accumulation) in PM muscle of Hanwoo could be due to its higher contents of Mb and mitochondria.
Lipid peroxidation may be involved in the pathogenesis of focal segmental glomerulosclerosis (FSGS). In the present study we examined whether lipid-soluble antioxidants, probucol and vitamin E, could inhibit renal injury in rats with chronic puromycin aminonucleoside (PA) nephrosis and dietary hypercholesterolemia by protecting lipoproteins from oxidation. Male Sprague-Dawley rats received six intraperitoneal injections of PA over a 10 week period and were fed a high cholesterol (HC) diet (PA-HC) or the same diet supplemented with either 1% probucol or vitamin E (100 IU/kg) for 32 weeks. For comparison, a group of rats received PA injections and a normal diet (PA-normal) with or without probucol or vitamin E. Another group rats received saline injections instead of PA and were fed a HC diet (Sal-HC) with or without probucol or vitamin E. At the end of the experiment, proteinuria, FSGS and tubulointerstitial lesions were present in the untreated rats with PA-HC or PA-normal. The magnitude of these lesions was significantly greater in the PA-HC rats than the PA-normal. In contrast to the PA-HC group with hypercholesterolemia, the PA-normal group did not show hypercholesterolemia from week 16 onwards. The rats with PA-HC alone showed significantly higher renal cortical malondialdehyde (MDA) levels and greater susceptibility of plasma very low density lipoprotein (VLDL) + low density lipoprotein (LDL) to the copper-mediated oxidation than the rats with PA-normal or Sal-HC alone. The administration of probucol or vitamin E in the rats with PA-HC significantly reduced the susceptibility of plasma VLDL + LDL to in vitro oxidation, renal cortical MDA level, proteinuria, mesangial volume density and magnitude of FSGS and interstitial lesions. Immunohistochemical staining of renal tissue showed focal segmental distribution of oxidized LDL (Ox-LDL) in the glomeruli of rats with PA-HC. Administration of probucol or vitamin E reduced the intensity of Ox-LDL staining. The staining with ED1 demonstrated that infiltrating glomerular macrophages were significantly more prevalent in the untreated rats with PA-HC than PA-normal or Sal-HC. Treatment with probucol or vitamin E significantly reduced the number of glomerular macrophages in the rats with PA-HC. These results suggest that alimentary hypercholesterolemia aggravates the renal damage in association with increased renal lipid peroxides in chronic PA nephrosis, and that dietary probucol or vitamin E attenuates renal injury in rats with PA-HC possibly by making lipoproteins resistant to oxidation and by inhibiting intraglomerular macrophage infiltration.
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