Endogenous Estrogen-Mediated Heme Oxygenase Regulation in Experimental Menopause

Figure 5

The effects of HO activity inhibition by tin-protoporphyrin-IX (SnPP) on the ST segment (measured in a lead II standard surface ECG, expressed in mV) following intravenous injection of epinephrine (10.0 μg/kg) and 30 s later phentolamine (15.0 mg/kg). The columns show significant decreases in the ST segment of ovariectomized and aged animals without SnPP treatment. SnPP pretreatment (30.0 μmol/kg, s.c., pH 7.4, 24 h and 1 h pretreatment) caused a significant ST depression in the sham-operated control animals. Following ovariectomy (POVX and OVX), or in aged rats, the SnPP treatment induced a more marked significant decrease in ST as compared with the control. Results are shown as means ± S.E.M., = 11–13. Statistical significance: ^* relative to the ovary-intact sham-operated control group; ^# a significant difference between groups with and without SnPP pretreatment; < 0.05 a significant difference between the data for the ovariectomized and aged groups after SnPP pretreatment and those for the controls.