Diurnal variation and exercise induced changes of prostacyclin in man

The diurnal variation and exercise induced changes in urinary 6 keto PGF1 alpha excretion were determined in 33 healthy, non-smoking volunteers. 6 keto PGF1 alpha was measured in urine using a validated RIA after extraction and purification steps. A definite diurnal variation of 6 keto PGF1 alpha excretion was found. The levels were higher during the day vs. night (169 +/- 13 ng/gram creatinine vs. 130 +/- 18, p less than 0.02) with daytime levels highest during the morning as compared with the afternoon (184 +/- 37 ng/gram creatinine, 0800-1200 hr vs. 130 +/- 14, 1600-2000, p less than 0.02). In addition, 60 minutes of strenuous exercise in well-trained and untrained volunteers significantly increased urinary 6 keto PGF1 alpha as compared to levels in urine collected during a similar time period while at rest (96 +/- 14 ng/gram creatinine to 147 +/- 27, p less than 0.05). The results suggest that urinary 6 keto PGF1 alpha excretion shows diurnal variation and increases with exercise in both trained and untrained subjects. Therefore, these factors need to be considered when interpreting and designing studies utilizing measurement of 6 keto PGF1 alpha in man.