Down regulation of the angiotensin II receptor subtype AT2 in human myometrium during pregnancy.

Samples of human myometrium have been collected during pregnancy and from non-pregnant women. Binding studies revealed the presence of a 50-fold higher density of angiotensin II AT2 receptor in the non-pregnant state than during gestation. Low levels of the AT1 receptor subtype (approx. 20 fmol/mg protein) were detected in both pregnant and non-pregnant myometrium. Outside pregnancy, the AT2 receptor accounted for greater than 95% of all angiotensin receptors, whereas during pregnancy the value dropped to about 40%. The down regulation of the human myometrial AT2 receptor during pregnancy may be related to the high hormonal content of the environment induced by gestation. The mechanism by which the AT2 receptor is regulated appears to be different to that of the AT1 receptor.