Measurement of individual plasma angiotensins in normal pregnancy and pregnancy-induced hypertension.

Abstract

Individual angiotensin peptides were measured by a high pressure liquid chromatography-RIA (HPLC-RIA) technique in the plasma of 20 nonpregnant women, 17 women with normal pregnancy, and 49 with pregnancy-induced hypertension. Immunoreactive angiotensin-II (ANG-II) consisted mainly of ANG-(1-8) octapeptide (greater than 65%), variable proportions (15-25%) of ANG-(4-8) pentapeptide, and small to negligible proportions of ANG-(2-8) heptapeptide and ANG-(3-8) hexapeptide. Levels of ANG-(1-8) were significantly higher in women with normal pregnancy than in both nonpregnant women (P less than 0.0006) and women with pregnancy-induced hypertension (P less than 0.008); in the latter, levels were lower with increasing severity of disease. Levels of ANG-(4-8) were higher in women with normal pregnancy than in women with pregnancy-induced hypertension or nonpregnant women. When expressed as a proportion of ANG-(1-8) levels, however, ANG-(4-8) levels were not higher in normal pregnancy than in women with pregnancy-induced hypertension or nonpregnant women. It is concluded that the well known increase in ANG-II levels in normal pregnancy relates predominantly to the active ANG-(1-8) octapeptide and to a far lesser extent to the smaller ANG peptides. Similarly, lower ANG-II levels in pregnancy-induced hypertension relate predominantly to lower ANG-(1-8) levels.