ALPHA-ADRENERGIC RECEPTORS IN HUMAN MYOMETRIUM - CHANGES DURING PREGNANCY

Myometrial biopsies from 80 women, delivered by cesarean section in 26 -42 completed weeks of pregnancy, were analyzed using radiolabeled alp ha1-antagonist [H-3]-prazosin and alpha2-antagonist [H-3]-rauwolscine. Statistical analysis was performed using Student's t test (two-tailed ), where p < 0.05 was considered significant. The number of alpha2-adr energic receptors did not vary (mean value weeks 37-39 = 17.2 +/- 1.3 fmol/mg protein), while the dissociation constant (K(d)) for alpha2-re ceptors tended to increase with increasing gestational age, implying r educed affinity near term (p < 0.05, mean values 3.4 +/- 0.2 nM). Alph a1-receptors, however, increased significantly (p < 0.01) in the pregn ancy weeks 3739 (mean value 29.2 +/- 2.9 fmol/mg prot) while K(d) was unaltered. Increased number of alpha1-receptors, along with a decrease d affinity of alpha2-receptors, could, in combination with other facto rs, play a role in the initiation of labor.