tokens: The mean dissociation constant ( Kd ) was similar in both sexes ( 1.35 +/- 0.70 x 10 ( -10 ) M in males , 1.13 +/- 0.66 x 10 ( -10 ) M in females ) , but the concentration of binding sites ( Nmax ) was significantly lower in females ( 2.32 +/- 0.92 fmol/10 ( 7 ) PBMC vs 4.43 +/- 1.38 fmol/10 ( 7 ) PBMC in males ; p = 0.0001 ) .