Release of beta-endorphin in response to physical exercise in non-pregnant and pregnant women.

The effect of physical exercise on beta-endorphin (beta-E) concentration in plasma was studied in 8 non-pregnant and in 8 pregnant women in their last trimester of pregnancy, using a 10-min bicycle ergometer test. In the non-pregnant women the mean beta-E levels were 2.4 +/- 0.7 (S.E.) pmol/l before the test, 4.3 +/- 0.9 pmol/l at the end of the test, and 4.3 +/- 0.6 and 5.0 +/- 2.0 pmol/l 15 and 30 min after the test, respectively, declining thereafter. In the pregnant women the mean beta-E values were 5.1 +/- 2.0 pmol/l before the test, 7.3 +/- 1.7 pmol/l at the end of the test, 6.7 +/- 2.0 pmol/l 15 min after the test, and 12.6 +/- 4.1 pmol/l 60 min after the test, declining thereafter. Thus, beta-E secretion increased in response to exercise both in non-pregnant and in pregnant women, the response lasting longer in pregnant women.