Abstract P090: Agonistic Autoantibodies to the Angiotensin II Type 1 Receptor Enhances ANG II Induced Renal Vascular Sensitivity and Reduces Renal Function During Pregnancy

Abstract

Preeclamptic women produce agonistic autoantibodies to the Angiotensin II type 1 receptor (AT1-AA) and exhibit increased blood pressure (BP) and vascular sensitivity to angiotensin II (ANG II). Although, together AT1-AAs and ANGII increase the BP, renal artery resistant index, and vasoconstriction of renal afferent arterioles in pregnant rats; the renal hemodynamics in the presence of the AT1-AAs during pregnancy has not been examined. Thus the objective of this study was to examine the changes in the glomerular filtration rate (GFR) and renal blood flow (RBF) during pregnancy in the presence of AT1-AAs and/or ANGII. Methods: Pregnant Sprague Dawley rats were divided into 4 groups: Normal Pregnant (NP, n=6), Pregnant + ANG II (Preg + ANG II, n=6), Pregnant + AT1-AA (Preg + AT1-AA, n=8), and Pregnant + ANG II + AT1-AA (Preg + ANGII + AT1-AA, n= 6). On day 13 of pregnancy, rats were implanted with mini-pumps infusing ANG II (50 ng/kg/min) and/or AT1-AA (1:40 dilution). On day 19 of pregnancy, rats were subjected to terminal renal function surgeries using FITC labeled Inulin. During the surgery, the BP was recorded and a transonic flowmeter probe was placed on the left renal artery to measure RBF. Results: BP was elevated in all pregnant rats administered ANG II and/or the AT1-AA. Although GFR was reduced, it was not significant between Preg + ANG II and Preg + AT1-AA vs. NP rats (1.5 ±0.24, 1.60 ±0.17 vs. 1.90 ±0.16 ml/min). However, the GFR was further decreased in Preg + ANGII + AT1-AA rats (1.20 ±0.08). No difference was observed with the RBF between Preg + ANG II and Preg + AT1-AA vs NP rats (14.4 ±2.96, 14.4 ±1.48 vs. 15.4 ±1.75 ml/min). RBF was decreased in Preg + ANGII + AT1-AA vs NP rats (7.4 ±1.09 vs. 15.4 ±1.75 ml/min). No change in RVR between Preg + ANG II and Preg + AT1-AA vs. NP rats (9.7 ±2.69, 8.3 ±0.58 vs. 6.4 ±0.77). However, the RVR was drastically increased between Preg + ANGII + AT1-AA vs NP rats (18.4 ±2.91 vs. 6.4 ±0.77). Conclusion: Together ANG II and AT1-AA drastically decreases renal function by 37%, RBF by 50%, and caused a 3 fold increase in RVR vs NP rats. These data indicate the importance of AT1-AAs to drastically enhance ANG II induced renal vascular sensitivity and reduce renal function during preeclampsia. Research Supported by T32HL105324 and RO1HD067541