Isoelectric heterogeneity of human prorenin (inactive renin) in body fluids

Using flat bed isoelectric focusing, inactive renins from various body fluids were compared. Normal plasma inactive renin demonstrated six consistent peaks at pH 4.98, 5.14, 5.29, 5.47, 5.63 and 5.91, the largest being 5.29, 5.47 and 5.63. The isoelectric pattern of ovarian follicular fluid inactive renin was similar, with slight shifts at major peaks to a higher pH. Pregnancy plasma had inactive renin patterns like normal human plasma as did pleural fluid, lymphocoele fluid and plasma from anephric humans. Amniotic fluid inactive renin showed a markedly different pattern with major peaks at pH 5.00, 5.16 and 5.30. Fetal plasma (cord blood) also showed differences with only four peaks at 5.24, 5.40, 5.58 and 5.83. We conclude that human prorenin isoelectric patterns are similar for plasma, ovarian and most tissue fluid prorenins, but different for fetal plasma and amniotic fluid suggesting that these forms of renin do not cross the placental barrier.