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

Abstract Background The purpose of this study was to determine the role of thromboxane A2 (TXA2) 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 TXA2) 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 mm 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 TXA2 receptors in this group. Conclusion These findings suggest that enhanced production of TXA2 does not play a major role in mediating the hypertension and renal vasoconstriction produced by chronic RUPP in pregnant rats.