Increased renal and vascular cytosolic phospholipase A2 activity in rats with cirrhosis and ascites

Indirect evidence suggests that the renal and vascular production of prostaglandins is increased in cirrhosis with ascites. However, the activity of the enzymes regulating the prostaglandin pathway has not been investigated in cirrhosis. The aim of the current study was to determine the activity of phospholipase A 2 (PLA 2 ), the key enzyme in the regulation of prostaglandin synthesis, in kidney and vascular tissue obtained from rats with carbon tetrachloride-induced cirrhosis and ascites (n = 9) and control rats (n = 6). PLA 2 activity was assayed in vitro using [ 14 C]arachidonyl-phosphatidylcholine (PC) and [ 14 C]arachidonyl-phosphatidylethanolamine (PE) as substrates in the presence of Ca 2+ . Kidneys from cirrhotic rats had significantly higher ALA I activity compared with control rats, with both PC and PE (35 ± 5 and 40 ± 6 vs. 21 ± 2 and 26 ± 3 pmol/mg/min, respectively; P <.05 for both). PLA 2 activity was increased in the renal cortex as well as in the renal medulla. Fractionation of the kidney extracts by Mono-Q anion-exchange chromatography showed that the elution position of PLA 2 activity corresponded to the cytosolic PLA 2 isoform (cPLA 2 ). Increased amounts of cPLA 2 protein were found in kidney extracts immunoblotted with an anti-cPLA 2 antibody. However, reverse-transcriptase polymerase chain reaction (RT-PCR) analysis did not detect any difference in cPLA 2 mRNA. PLA 2 activity was also higher in aortic tissue from cirrhotic rats than in controls (PC 38 ± 5 vs. 26 ± 1 and PE 66 ± 8 vs. 41 ± 3 pmol/mg/min; P <.05 for both). Incubation of renal and aortic extracts from cirrhotic rats with anti-cPLA 2 antibody reduced PLA 2 activity by 64% and 88%, respectively. In conclusion, PLA 2 activity is increased in kidneys and vascular tissue from cirrhotic rats with ascites. This can be accounted for by an induction of CPLA 2 , which would mediate, at least in part, the increased renal and vascular production of prostaglandins in cirrhosis.