The measurement of apolipoprotein A-I and A-II levels in men and women by immunoassay

precise, and accurate immunodiffusion assay was de-veloped and applied in a population sample of in-dustrial employees. Apolipoprotein A-II (A-II) did not increase with age in men (r =-0.20, n = 172), but showed a slight increase with age in women (0.1 mg/dl per yr, r = 0.20, n = 188). A-II correlated sig-nificantly with apolipoprotein A-I (A-I) (r = 0.71) and high density lipoprotein (HDL) cholesterol (men, r = 0.64; women, r = 0.49). The A-I/A-II ratio was significantly related to HDL cholesterol (men, r = 0.29; women, r = 0.44). Women on no medication (n = 92) had A-II levels similar to men (34+5 and 33+5 mg/dl, mean±+SD, respectively), whereas women on oral contraceptives or estrogens had significantly higher levels (39±6 mg/dl, n = 75, P < 0.01). The plasma A-I/A-Il weight ratio was 3.6±0.4 for men and 3.8±0.5 for women. In the d = 1.10-1.21 subfraction, both males and females had similar A-I, A-II, and HDL cholesterol levels (men: mean, 97, 27, and 32 mg/dl, respectively; women: mean, 104, 28, and 36 mg/dl, respectively). Women had approximately twice the amount of A-I, A-II, and HDL cholesterol than men in the d = 1.063-1.10 fraction (men: mean