Enhanced thromboxane synthesis during chronic reductions in uterine perfusion pressure in pregnant rats

Background: The purpose of this study was to determine the role of thromboxane A(2) (TXA(2)) in a conscious, chronically instrumented rat model of pregnancy-induced hypertension (PIH) produced by chronic reductions in uterine perfusion pressure (RUPP). Methods: Mean arterial pressure (MAP), glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and 24-h urinary excretion of TXB2 (metabolite of TXA(2)) were determined in normal pregnant rats and RUPP pregnant rats. Results: At day 20 of pregnancy, RUPP rats showed a significantly (P < .05) higher MAP (125 +/- 3 turn Hg v 100 +/- 2 mm Hg) as compared with normal pregnant controls. The elevation in arterial pressure in RUPP group was associated with a marked increase (P < .05) in the urinary concentration of TXB2 compared with normal pregnant group (3663 +/- 488 v 2646 +/- 257 pg/24 h). Baseline GFR (1.74 +/- 0.13 v 2.40 +/- 0.20 mL/min, respectively, P < .05) and ERPF (5.13 +/- 0.44 v 6.44 +/- 0.58 mL/min, respectively) were decreased in RUPP rats relative to pregnant controls. Infusion of a TX receptor antagonist, SQ 29,548 (2 mg/kg bolus plus 2 mg/kg per h infusion) had no significant effect on increased MAP in RUPP pregnant rats. Similarly, ERPF and GFR did not change during acute blockade of TXA(2) receptors in this group. Conclusion: These findings suggest that enhanced production of TXA(2) does not play a major role in mediating the hypertension and renal vasoconstriction produced by chronic RUPP in pregnant rats. (C) 2002 American Journal of Hypertension, Ltd.