• endothelin-1
• creatine kinase

Endothelin-1 (ET-1), a potential vasoconstrictor peptide, may contribute to the exercise induced redistribution of blood flow in muscles.^1,2 On the other hand, the latter parameter in athletes may be expanded secondary to muscle volume and as a consequence of increased ET-1 production.³ In this study, we found a difference in basal serum ET-1 levels between trained male athletes and normal matched male controls.

We studied 13 male professional football players (mean (SEM) age 27 (1.02) years; mean (SEM) body mass index 24.2 (1.2) kg/m²) and an equal number of sedentary or moderately physically active men (age 26 (1.3) years; body mass index 24.4 (1.8) kg/m²). All subjects gave written consent and had a negative family history of diabetes and hypertension. Blood samples were collected at 8 am after an overnight fast; all subjects remained at rest for 20 minutes in a supine position, before collection of the blood specimen. ET-1 concentration in serum was measured by radioimmunoassay (Peninsula Lab Inc, Belmont, California, USA). Data were analysed by Student's t test for independent samples.

The concentration of ET-1 in the serum was significantly higher in the athletes than control subjects (22.16 (0.87) v 7.74 (0.29) pg/ml, p<0.001; values are mean (SEM)). Serum creatine kinase was also found to be significantly higher in athletes than controls (331.84 (43.3) v 110.5 (17.3) U/l, p<0.001; values are mean (SEM)).

The increased creatine kinase levels may be attributed to the increased muscle mass in athletes, and the increased serum ET-1 levels can be explained as being a consequence of a widening of the vascular bed resulting from the increased muscle weight and size.