Serum platelet-activating factor acetylhydrolase (PAF-AH) activity in more than 3000 healthy Japanese.

A spectrophotometric assay for platelet-activating factor acetylhydrolase (PAF-AH) activity differs from the radioisotopic assay in its value because of a difference in substrate specificity. The spectrophotometric assay is more precise than the radioisotopic assay, providing information that is not clear with the radioisotopic assay. We measured the serum PAF-AH activity in 3106 healthy Japanese, utilizing the spectrophotometric assay with an Hitachi 7170 automatic analyzer. We also measured the serum PAF-AH activity in 18 healthy volunteers to investigate the effect of diet and the change in activity in a day and over 6 weeks. Changes were examined at 0 (day 1), 1, 2, 4 and 6 weeks. The mean value for females was significantly lower than that of males at the 5% level and both male and female activity had a tendency to increase with advancing age. It is known that the PAF-AH is primarily associated with LDL in blood and the PAF-AH activity correlated with the total cholesterol (r=0.52, n=126) and the LDL cholesterol (r=0.60, n=126) concentrations. In the diet study, there was no observable effect on activity. No difference in PAF-AH activity was observed between serum and plasma sample types. The serum PAF-AH activity was stable at 7 degrees C for at least 7 days and at -20 degrees C for at least 2 months. The serum PAF-AH activity in women was lower than in men until the menopausal age was reached. We could use not only fresh fasting serum, but also plasma sample, non-fasting sample and stored sample to estimate the PAF-AH activity.