Blood lipid profile and myocardial superoxide dismutase in swim-trained young and middle-aged rats: comparison between left and right ventricular adaptations to oxidative stress.

Region-wise interactive effects of age, swim intensity, and duration on exercise performance in the myocardium and serum lipid profile in young (4 months) and middle-aged (12 months) rats were examined. Animals were allocated to the sedentary control (SE-C) or one of the nine trainee groups. Swim training was for 6 days/week and for 4 weeks at 3 durations (20, 40, and 60 min/day) and intensities (2%, low; 3%, medium; 5%, high). Swim velocity and external work showed an age-related decline with low-intensity of 20 min/day in the middle aged. Reduction in serum cholesterol, low-density lipoproteins (LDLs), and triglycerides were accompanied by elevated levels in high-density lipoprotein in the low-to-moderately trained ones for 20 and 40 min/day. Training at 2%, intensity for 20 min/day was sufficient to alter the blood lipid profile and improve swim performance, and endurance in terms of blood lactate. A concomitant increase in Mn-superoxide dismutase (Mn-SOD) activity and reduced malondialdehyde in the left ventricle (LV) and right ventricle (RV) were evident. Lipofuscin was higher in the LV compared to RV. Our results reflect the minimization of free radical generation through appropriate exercise protocols. Our findings on improved blood lipid profile could be related to lower free radicals, which would otherwise oxidize LDLs. Further, swim training when initiated in the young and middle age for as low as 20 min/day at 2% intensity improves the Mn-SOD in the LV and RV. However, the adaptive response of the LV was weaker when compared to the RV, more so in the middle aged.

Swim exercise training and adaptations in the antioxidant defense system of myocardium of old rats: relationship to swim intensity and duration.

We examined a suitable swim program of different intensities and durations that could evoke changes in the myocardial antioxidant capacity in 22-month-old rats. Male rats (Rattus norvegicus) were assigned to either a sedentary control (SE-C) group or one of six trainee groups. Animals were swim-exercised for 4 weeks with either 20 min or 40 min/day, and three intensities, low, moderate and high. Low-intensity at 20 min/day elicited maximum swim velocity (Sv) and endurance capacity (P<0.05). While serum total cholesterol, triglyceride and low-density lipoprotein (LDL-C) levels were significantly reduced, high-density lipoprotein (HDL-C) showed an increase (P<0.05) in low-intensity trained rats (20 min/day) over SE-C. Notable reduction in blood lactate was also evident. Exercise training significantly increased superoxide dismutase (Mn-SOD), decreased lipid peroxidation products, malondialdehyde and lipofuscin in the left and right ventricles. Increased Mn-SOD with concomitant decrease in lipofuscin in left ventricle was significantly greater than in right ventricle. Moderate- to high-intensity exercise was not effective in either reducing lipid peroxidation products or elevating Mn-SOD activity. These data suggest that swim training at low-intensity of 20 min/day is beneficial as a major protective adaptation against oxidative stress in old myocardium.

Effect of smoking on phenylbutazone disposition.

A single oral dose of 6 mg phenylbutazone/kg body wt. was administered to seven cigarette smokers and to seven healthy male volunteers serving as control. Plasma phenylbutazone half-life (t1/2 beta) was shortened significantly (p less than 0.05) in the cigarette smokers as compared to the non-smoker control group. Phenylbutazone was cleared from the blood significantly faster (p less than 0.06) in the smoking group than in the non-smoking group.