CONCOMITANT INCREASE IN BLOOD-PLASMA LEVELS OF IMMUNOREACTIVE HEMORPHIN-7 AND BETA-ENDORPHIN FOLLOWING LONG-DISTANCE RUNNING

Hemorphins are endogenous opioids derived by enzymatic degradation of hemoglobin, a protein released in blood plasma during long distance ru nning. We examined levels of beta-endorphin and the heptapeptide hemor phin-7, in heparinized venous blood plasma from 15 sedentary controls (8 males, 7 females) and from 15 age- and sex-matched marathon runners at baseline and after running 42 km or 21 km. Baseline levels of beta -endorphin (range 0.2-4.3 fmol/ml) were neither dependent upon weight, body mass index weight/height2, running status nor sex. Baseline leve ls of hemorphin-7 (range 0.2-6.9 pmol/ml) were lower in women (P < 0.0 4) and covariated positively with body weight (P = 0.06), explaining l ower levels in runners by their lower body weight. Covariation with bo dy mass index was positive, but not significant (P = 0. 10), however, here the dependence upon sex appeared stronger (P = 0.014). Running in duced significant and correlated increases in hemorphin-7 and beta-end orphin (r = 0.74; P < 0.002), possibly indicating a functional relatio nship between these two peptides.