ABOUT 8-HOUR VARIATION OF CIRCULATING HUMAN ENDOTHELIN-1

Plasma endothelin-1 (ET-1) and cortisol were measured around the clock at hourly intervals on 7 clinically healthy, diurnally active, noctur nally resting subjects 22-27 years of age. The circadian rhythm in cor tisol is demonstrated for each subject (p less than or equal to 0.020) as well as on a group basis (p = 0.002), peaking in the morning. By c ontrast, the circadian variation of ET-I is statistically significant in only one of the subjects, and it is not detected for the group as a whole (p > 0.20). Instead, ET-1 is characterized by an about 8-h comp onent (p < 0.001) that is not found for cortisol. (C) 1998 Elsevier Sc ience Inc.