INCREASED RENAL AND VASCULAR CYTOSOLIC PHOSPHOLIPASE A(2) ACTIVITY INRATS WITH CIRRHOSIS AND ASCITES

Indirect evidence suggests that the renal and vascular production of p rostaglandins is increased in cirrhosis with ascites. However, the act ivity of the enzymes regulating the prostaglandin pathway has not been investigated in cirrhosis. The aim of the current study was to determ ine 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 asc ites (n = 9) and control rats (n = 6). PLA(2) activity was assayed in vitro using [C-14]arachidonyl-phosphatidylcholine (PC) and [14C]arachi donyl-phosphatidylethanolamine (PE) as substrates in the presence of C a2+. Kidneys from cirrhotic rats had significantly higher PLA(2) activ ity 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 ani on-exchange chromatography showed that the elution position of PLA(2) activity corresponded to the cytosolic PLA(2) isoform (cPLA(2)). Incre ased amounts of cPLA(2) protein were found in kidney extracts immunobl otted with an anti-cPLA(2) antibody. However, reverse-transcriptase po lymerase chain reaction (RT-PCR) analysis did not detect any differenc e in cPLA(2) mRNA. PLA(2) activity was also higher in aortic tissue fr om 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 rena l and aortic extracts from cirrhotic rats with anti-cPLA, antibody red uced PLA, activity by 64% and 88%, respectively. In conclusion, PLA(2) activity is increased in kidneys and vascular tissue from cirrhotic r ats with ascites. This can be accounted for by an induction of cPLA(2) , which would mediate, at least in part, the increased renal and vascu lar production of prostaglandins in cirrhosis.