ASCORBATE PROTECTS GUINEA-PIG TISSUES AGAINST LIPID-PEROXIDATION

In recent years we and others have shown that ascorbic acid (AH(2)) is a potential scavenger of superoxide ( O-2(.-)) and peroxyl (LOO(.)) r adicals, the species involved in lipid peroxidation (LPO)in animal tis sues. In this paper we have demonstrated that AH(2) protects guinea pi g tissues from LPO both in vive and in vitro. The extent of LPO has be en determined by estimating malonaldehyde using the thiobarbituric aci d test and HPLC and also by measuring the accumulation of fluorescent pigment and occurrence of protein changes in the microsomal membranes. In AH(2)-deficiency, LPO occurs progressively in guinea pig tissues, despite the presence of adequate levels of antioxidants like alpha-toc opherol, GSH, protein thiols, and scavenging enzymes, namely, superoxi de dismutase, catalase, and glutathione peroxidase. In a model in vitr o system, microsomal LPO initiated by O-2(.-) is completely prevented by AH(2) but not by alpha-tocopherol, GSH, uric acid, and catalase. AH (2) is also the most effective antioxidant in preventing microsomal LP O mediated by tert-butylhydroperoxide or the chain propagating species LOO(.), generated from 2,2'-azobis (2-amidinopropane) hydrochloride. The results, obtained with guinea pigs may be applicable to humans, be cause humans are also dependent on dietary AH(2). Our data suggest tha t an adequate vitamin C nutrition may prevent common cellular degenera tive diseases associated with LPO.