Submitted on August 18, 2004
Accepted on March 26, 2005
Impact of aging on muscle blood flow in chronic heart failure
Kevin E Eklund1, Karen S Hageman1, David C Poole1, and Timothy I Musch1*
1 Kinesiology, Anatomy & Physiology, Kansas State University, Manhattan, KS, USA
* To whom correspondence should be addressed. E-mail: musch{at}vet.ksu.edu.
Chronic heart failure (CHF) is manifested principally in the elderly population. Therefore, to understand the causes of exercise intolerance in CHF patients, it is imperative to resolve the effects of aging on muscle blood flow (BF) in CHF. To address this issue, we determined the muscle BF response to submaximal treadmill exercise (20m/min, 5% grade) in young (YCHF: 6-8 mo, 412±11 g, n=11) and old (OCHF: 27-29 mo, 494±10 g, n=8) Fischer 344/Brown Norway rats with similar degrees of myocardial infarction-induced left ventricular (LV) dysfunction: resting LV end-diastolic pressure, YCHF, 24±2; OCHF, 22±2 mmHg; LV dP/dt, YCHF, 5168±285; OCHF, 5050±165 mmHg/s; lung weight normalized to body weight, YCHF, 9.14±0.72; OCHF, 8.21±0.29 mg/g (all P>0.05). The exercising HR response was blunted in OCHF when compared to YCHF rats (YCHF, 454±8; OCHF, 395±9 bpm, P<0.05). BF (radiolabelled microspheres) to the total hindlimb musculature and to each of the 28 individual muscles examined was similar between YCHF and OCHF rats under resting conditions. During exercise, BF to 5 of the hindlimb muscles that normally possess a majority of slow-twitch oxidative (SO) and fast-twitch oxidative glycolytic (FOG) muscle fibers increased significantly less (-25 to -42%) for OCHF compared to YCHF rats. In contrast, BF to 14 of the hindlimb muscles that normally possess a majority of fast-twitch glycolytic (FG) muscle fibers was increased (+22 to +337%) for OCHF versus YCHF rats which contributed to a greater msss specific total hindlimb BF response in OCHF rats (YCHF, 78±5; OCHF, 100±11 ml/min/100g, P>0.05) and coincided with greater reductions in BF to the kidneys and splanchnic organs during exercise in OCHF versus YCHF. In conclusion, there appears to be a profound age-related redistribution of BF from the highly oxidative to the highly glycolytic muscles of the hindlimb during exercise in OCHF compared to YCHF rats. This phenomenon is qualitatively similar to that reported previously for healthy Y and O rats.
