Angiotensin-(1-7) in the ovine fetus

In the adult animal, ANG-(1-7) may counterbalance some effects of ANG II. I ts effects in the fetus are unknown. Basal ANG-(1-7), ANG I, ANG II, and re nin concentrations were measured in plasma from ovine fetuses and their mot hers (n = 10) at 111 days of gestation. In the fetus, concentrations of ANG I, ANG-(1-7), and ANG II were 86 +/- 21, 13 +/- 2, and 14 +/- 2 fmol/ml, r espectively. In the ewe, concentrations of ANG I were significantly lower ( 20 +/- 4 fmol/ml, P< 0.05) as were concentrations of ANG-(1-7) (2.9 +/- 0.6 fmol/ml), whereas ANG II concentrations were not different (10 +/- 1 fmol/ ml). Plasma renin concentrations were higher in the fetus (4.8 +/- 1.1 pmol ANG I.ml(-1).h(-1)) than in the ewe (0.9 +/- 0.2 pmol.ml(-1).h(-1), P< 0.0 5). Infusion of ANG-(1-7) (similar to9 mug/h) for a 3-day period caused a s ignificant increase in plasma concentrations of ANG-(1-7) reaching a maximu m of 448 +/- 146 fmol/ml on day 3 of infusion. Plasma levels of ANG I and I I as well as renin were unchanged by the infusion. Urine flow rate, glomeru lar filtration rate, and fetal arterial blood pressure did not change and w ere not different than values in fetuses receiving a saline infusion for 3 days (n = 5). However, the osmolality of amniotic and allantoic fluid was s ignificantly higher in fetuses that received ANG-(1-7). Also, compared with the saline-infused animals, mRNA expression levels of renin, the AT(1) rec eptor, and AT(2) receptor were elevated in kidneys of fetuses that received infusions of ANG-(1-7). Infusion of an ANG-(1-7) antagonist {[D-Ala(7)]ANG -(1-7), 20 mug/h} for 3 days had no effect on fetal blood pressure or renal function. In conclusion, although infusion of ANG-(1-7) did not affect fet al urine flow rate, glomerular filtration rate, or blood pressure, changes in fetal fluids and gene expression indicate that ANG-(1-7) may play a role in the fetal kidney.