THE ROLE OF MEMBRANE-COMPOSITION IN ATPASE ACTIVITIES OF CIRRHOTIC RAT-LIVER - EFFECT OF SILYMARIN

The activities of Ca2+‐ and Na+, K+ ‐ATPases were studied in liver plasma membranes from CCI4‐cirrhotic rats and from livers of rats treated with silymarin in addition to CCI4. CCI4 chronic treatment produced significant decreases in Na+, K+‐ and Ca2+‐AT Pase activities; however, the animals treated with silymarin along with CCI4 showed no differences in ATPase activities as compared to controls. The lipid analysis performed in plasma membranes revealed increases in the cholesterol/phospholipid (CH/PL) and sphingomyelin/phosphatidylcholine (SM/PC) ratios in the cirrhotic group. Again, the membranes isolated from rats receiving CCI4 + silymarin showed normal CH/PL and SM/PC values. Considering that CH/PL and SM/PC ratios are related to membrane microviscosity, this study suggests that a lower fluidity of the membrane may be responsible for the observed decreases in ATPase activities in the cirrhotic group. Additionally, the role of silymarin to improve liver function in CCI4‐cirrhosis can be attributed partially to its action at membrane level by preventing the increases in CH/PL and SM/PC ratios. Copyright © 1990 John Wiley & Sons, Ltd.