The effects of chronic intermittent hypoxia on blood pressure and myocardial mitochondrial oxidative stress in aged rats / 中华老年医学杂志

ABSTRACT

Objective To investigate the effect of chronic intermittent hypoxia on blood pressure,sympathetic nerve activity and myocardial mitochondrial oxidative stress status in aged rats.Methods Chronic intermittent hypoxia(CIH)rat models were established.A total of 84 male Wistar rats(3-4 and 23-24 months old,respectively)were randomly and equally divided into four groups according to ageyoung control group,young CIH group,aged control group and aged CIH group.CIH exposure lasted for 3 weeks.The arterial blood pressure,the frequency of carotid sinus nerve action potential,the lung function,the levels of catecholamine,aconitase/fumarate ratio (A/F),plasma superoxide dismutase(SOD)in the plasma were measured and compared between four groups.Results The arterial blood pressure was significantly higher in young CIH group than in the young control group[(150.4 ±25.6)mmHg vs.(102.2±7.4)mmHg,P＜0.01].There was no significant difference in the arterial blood pressure between the aged CIH group[(132.8 ±16.2) mmHg] and the aged control group[(127.1 ± 26.8)mmHg].The minute volume ventilation was significantly lower in the aged control group than in young controlgroup[(331.7±53.5)ml· min-1 · kg-1vs.(554.8±111.9)ml· min-1 · kg-1P＜0.05].The min-1 · kg-1 ventilation showed no significant difference between the agedCIH group[(354.1±51.9)ml· min-1 · kg-1]and the aged control group[(331.7 ±53.5)ml· min-1 · kg-1].The rate of CSN frequency change by hypoxia stimulation was lower in the aged control group than in young control group[(6.2± 5.5)times vs.(11.8 ±6.6)times,P＜0.01],and was lower in the aged CIH group than in the young CIH group[(22.2 ± 13.5) times vs.(44.2± 12.1) times,P＜0.01].The levels of plasma norepinephrine and epinephrine were higher in the young CIH group than in the control group[(39.0±8.9)nmol/L vs.(20.8±10.6)nmol/L,(48.1±13.6)nmol/L vs.(26.7 ± 14.3)nmol/L,both P＜0.05].The levels of plasma norepinephrine and epinephrine showed no significant difference between the aged control group and the young control group,also no significant difference was found between the aged CIH group and the aged control group.The A/F ratio was lower in the young CIH group than in the young control group[(0.26±0.13)vs.(0.58 ±0.04),P＜0.01].The A/F ratio was lower in the aged control group than in the young control group [(0.29±0.02)vs.(0.58± 0.04),P＜0.01],but there was no significant difference in the A/F ratio between the aged CIH group and the aged control group.The level of SOD was significantly lower in the young CIH group than in the young control group [(5.30 ±± 0.90) NU/mgprot vs.(6.10 ± 1.73)NU/mgprot,P＜0.05].There was no significant difference in SOD level between aged control group and aged CIH group.Conclusions The effect of CIH on blood pressure in aged rats is different from the youth rats.This study shows adecreasedsympathetic nervous over activity and a reducedmitochondrial oxidative stress in aged rats.Aging probably suppresses two important pathogenic mechanisms,by which CIH affects blood pressure,therefore releases CIH induced blood pressure abnormality.