Abstract: Objective To investigate the therapeutic effects of hemin, an inducer of heme oxygenase, in a rat model of gestational
hypertension and explore the possible mechanism. Methods Eighteen 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 (sFIt-1) and vascular endothelial growth
factor (VEGF) level in the placental tissue homogenate supernatant were detected using ELSIA. Results At 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
sFIt-1 was significantly higher and VEGF level significantly lower in the model group than in the other two groups (P<0.05);
sFIt-1 level remained higher and VEGF lower in hemin group than in the control group (P<0.05). Conclusion Hemin can
reduce blood pressure and urinary protein in rats with gestational hypertension possibly by up-regulating HO activity,
enhancing carbon monoxide production, reducing sFIt-1 and increasing VEGF in the placental tissue.