We measured the concentration of beta -endorphin (beta -End) in plasma, as
well as in aqueous humor and crystalline lens removed during cataract surge
ry. beta -End was detected both in the aqueous humor and in the crystalline
lens. The concentration of beta -End in the aqueous humor corresponded to
almost the half of the plasma level (2.18 fmol/l and 4.55 fmol/l). Endogeno
us beta -End is presumed to enter the intraocular structures by passive dif
fusion. (C) 2001 Elsevier Science inc. All rights reserved.