A study of the temporal relationship between plasma high molecular weight angiotensinogen and the development of pregnancy-induced hypertension

In addition to the normally prevalent low molecular weight angiotensinogen (LM(r)A), significant quantities of a high molecular weight angiotensinogen (HM(r)A) are present in the human pregnant state. Previous studies have do cumented that 47% of women who develop pregnancy-induced hypertension (PIH) have a significantly elevated plasma HM(r)A/LM(r)A ratio. The purpose of t his study is to establish whether or not the increase in the HM(r)A/LM(r)A ratio precedes the development of hypertension. Serial plasma samples were collected from a group of women throughout their pregnancy. High molecular weight angiotensinogen and LM(r)A levels in the samples from these women we re determined. Fifteen of these women developed PIH. Seven women in the PIH group had a significantly elevated plasma HM(r)A/LM(r)A ratio. There was n o consistent relationship between the elevation of the HM(r)A/LM(r)A ratio and the onset of hypertension. Three women had an elevated HM(r)A/LM(r)A ra tio before the development of hypertension. In one woman the two events occ urred simultaneously, and in three women the HM(r)A/LM(r)A ratio was elevat ed only after the development of hypertension. The current study shows that the development of hypertension during pregnancy is not the primary biolog ic signal for elevation of the plasma HM(r)A/LM(r)A ratio. Other parameters associated with fetal distress or abnormal development of placental circul atory systems must be involved in increasing the HM(r)A/LM(r)A ratio. It is proposed that the elevation of the HM(r)A/LM(r)A ratio is a mechanism by w hich the placental tissue specific renin-angiotensin system is attenuated. (C) 2001 American Journal of Hypertension, Ltd.