Green tea catechin improves microsomal phospholipase A₂ activity and the arachidonic acid cascade system in the kidney of diabetic rats

The purpose of this study was to investigate the effects of green tea catechin on the microsomal phospholipase A₂ activity and arachidonic acid cascade in the kidneys of streptozotocin-induced diabetic rats. Sprague-Dawley male rats weighing 100 ± 10 g were assigned randomly to one normal and three streptozotocin-induced diabetic groups. The diabetic groups were the DM-0C group (n = 10), fed a catechin-free diet, the DM-0.25C group (n = 10), fed a 0.25 g catechin per 100 g diet, and the DM-0.5C group (n = 10), fed a 0.5 g catechin per 100 g diet. The kidney microsomal phospholipase A₂ activity was higher in the diabetic groups than in the normal group, while it was lower in the DM-0.25C and DM-0.5C groups than in the DM-0C group. The percentage of phosphatidylcholine hydrolysed in the kidney microsomes was not significantly different between any of the four groups. The percentage of phosphatidylethanolamine hydrolysed in the kidney microsomes was progressively higher in the DM-0.5C, DM-0.25C and DM-0C groups, respectively, compared to the normal group. The formation of thromboxane A₂ was significantly higher while the formation of prostacyclin was lower in kidney microsomes of the streptozotocin-induced diabetic groups compared with the normal group, but this condition was improved by catechin supplementation. Kidney microsomal vitamin E concentrations were progressively lower in the DM-0.5C, DM-0.25C, and DM-0C groups, respectively, compared to the normal group. The kidney thiobarbituric acid reactive substance (TBARS) contents became higher in the DM-0C and DM-0.25C groups as compared with the normal group, whereas the DM-0.5C group did not differ from the normal group. Kidney function appears to be improved by green tea catechin supplementation due to its antithrombus action, which in turn controls the arachidonic acid cascade system.