Serum platelet-activating factor acetylhydrolase (PAF-AH) activity in patients with hyperbilirubinemic hepatobiliary disease.

Platelet-activating factor acetylhydrolase (PAF-AH) is an enzyme that catalyzes hydrolysis of PAF and is important for regulation of serum PAF concentration. Twenty-seven patients with hyperbililubinemic hepatobiliary diseases (eight patients with liver cirrhosis, five with acute hepatitis and 14 with obstructive cholestasis) were studied. Serum PAF-AH activity was elevated in hyperbilirubinemic condition associated with liver cirrhosis, obstructive cholestasis or acute hepatitis. There was a significant correlation of serum PAF-AH activity with serum cholesterol (r=0.891, P=0.014 in liver cirrhosis, r=0.813, P=0.002 in obstructive cholestasis) or low density lipoprotein (LDL) cholesterol (r=0.771, P=0.007 in obstructive cholestasis). Serum PAF-AH activity/cholesterol ratio and PAF-AH activity/LDL cholesterol ratio were elevated in the three types of hyperbilirubinemic liver disease. LDL cholesterol increased and PAF-AH/LDL cholesterol ratio decreased in acute hepatitis after remission. On the other hand, LDL cholesterol decreased and PAF-AH/LDL cholesterol ratio did not change after treatment in obstructive cholestasis. These findings suggest that, though serum LDL is a factor influencing serum PAF-AH activity in obstructive jaundice, other factors, i.e. reduced biliary PAF-AH excretion, may also influence serum PAF-AH activity in hyperbilirubinemic hepatobiliary diseases.