Catechol-O-methyltransferase activity in red blood cells in threatened preterm labor; effect of indomethacin and nylidrin

Catecholamines that are released in excess during human labor are inactivated mainly by catechol-O-methyltransferase (COMT). To ascertain whether uterine contractions are associated with changes in COMT activity in red blood cells (RBCs), we studied 25 women with established threat of preterm labor between 25 and 33 weeks of gestation, 25 gestational age-matched control women not experiencing uterine contractions, 25 women who were in term labor, and 25 non-pregnant healthy women. COMT activity in pregnant women without uterine contractions (median 0.3, range 0.1-0.8 pmol/mg/min) was lower (p less than 0.05) than that in non-pregnant control series (median 0.5, range 0.3-0.7 pmol/mg/min). RBCs' COMT activity in women with preterm labor (median 0.6, range 0.2-1.1 pmol/mg/min) was greater (p less than 0.05) than that in pregnant and non-pregnant control women, but similar to that during term labor (median 0.5, range 0.2-1.7 pmol/mg/min). Women with preterm labor were treated with indomethacin (12 women) or nylidrin (13 women). Nylidrin treatment was accompanied by a 35% rise in COMT activity 3 h later, whereas indomethacin caused no significant change. Apart from cessation of uterine contractions during tocolysis, 13 women went into labor before the 37th gestational week, but their pretreatment COMT activity (median 0.7, range 0.2-1.1 pmol/mg/min) did not differ from COMT activity in women whose pregnancy proceeded to term (median 0.5, range 0.3-1.0 pmol/mg/min).(ABSTRACT TRUNCATED AT 250 WORDS)