Cardiac function and plasma corticosterone are altered in rats submitted to chronic intermittent hypoxia (CIH)

Abstract

Rats submitted to CIH present significant changes in the cardiovascular system by mechanisms that are not completely understood. In the present study, adult rats were submitted to CIH (FiO2 of 6% during 40 s, every 9 min, 8 h/day) during 35 days (CIH rats, n = 39) and a mild but significant increase in the mean arterial pressure (MAP, 114 ± 2 vs 104 ± 1 mmHg) was observed in comparison to control rats (n = 35) maintained under normoxia. Cardiac output (CO), evaluated by the thermodilution method and adjusted by the tibial length, was significantly smaller in the CIH group than in the control group (34.5 ± 3.5 vs 49.7 ± 3.7 mL/min/cm). Total peripheral resistance, calculated by MAP/CO ratio, was higher in CIH rats than in control rats (3.19 ± 0.52 vs 2.04 ± 0.15 PRU). Heart weight evaluation showed that CIH rats presented an increase in both right (0.61 ± 0.02 vs 0.55 ± 0.02 g/kg) and left ventricles (2.08 ± 0.06 vs 1.90 ± 0.04 g/kg). Another important finding in the CIH group was the significant increase in plasma corticosterone in comparison to control group (38 ± 4 vs 20 ± 2 μg/dL). These data suggest that the increase in MAP observed in rats submitted to CIH is associated to an increase in vascular resistance and the plasma corticosterone levels could contribute to this increase. The reduction in CO combined with the cardiac hypertrophy may explain, at least in part, why CIH rats present a mild increase in MAP. Supported by FAPESP and CNPq.