OBJECTIVETo investigate the therapeutic effects of hemin, an inducer of heme oxygenase, in a rat model of gestational hypertension and explore the possible mechanism.

METHODSEighteen pregnant SD rats at day 12 of gestation were randomized equally into gestational hypertension model group, hemin treatment group, and normal pregnancy (control) group. In the former two groups, the rats were subjected to daily nitro-L-arginine methyl ester (L-NAME, 80 mg/kg) gavage since gestational day 14 for 7 consecutive days to induce gestational hypertension; saline was administered in the same manner in the control rats. The rats in hemin group received daily intraperitoneal injection of hemin (30 mg/kg) starting from gestational day 16. HO activity and carboxyhemoglobin (COHb) level in rat placental tissue were detected with spectrophotometric method, and soluble vascular endothelial growth factor receptor-1 (sFlt-1) and vascular endothelial growth factor (VEGF) level in the placental tissue homogenate supernatant were detected using ELSIA.

RESULTSAt gestational day 20, the blood pressure and 24-h urinary protein were significantly higher in the model group than in the other two groups (P<0.05), and were higher in hemin group than in the control group (P<0.05); HO activity and COHb content in the placenta tissue were the lowest in the model group (P<0.05), and was lower in hemin group than in the control group (P<0.05). The level of sFlt-1 was significantly higher and VEGF level significantly lower in the model group than in the other two groups (P<0.05); sFlt-1 level remained higher and VEGF lower in hemin group than in the control group (P<0.05).

CONCLUSIONHemin can reduce blood pressure and urinary protein in rats with gestational hypertension possibly by up-regulating HO activity, enhancing carbon monoxide production, reducing sFlt-1 and increasing VEGF in the placental tissue.