title: Effects of chronic heart failure in rats on the recovery of microvascular PO2 after contractions in muscles of opposing fibre type.
abstract: Chronic heart failure (CHF) impairs muscle O2 delivery (QO2) and, at a given O2 uptake (VO2), lowers microvascular O2 pressures (PmvO2: determined by the QO2-to-VO2 ratio), which may impair recovery of high-energy phosphates following exercise. Because CHF preferentially decreases QO2 to slow-twitch muscles, we hypothesized that recovery PmvO2 kinetics would be slowed to a greater extent in soleus (SOL: approximately 84% type I fibres) than in peroneal (PER: approximately 14% type I) muscles of CHF rats. PmvO2 dynamics were determined in SOL and PER muscles of control (CON: n= 6; left ventricular end-diastolic pressure, LVEDP: approximately 3 mmHg), moderate CHF (MOD: n= 7; LVEDP: approximately 11 mmHg) and severe CHF (SEV: n= 4; LVEDP: approximately 25 mmHg) following cessation of electrical stimulation (180 s; 1 Hz). In PER, neither the recovery PmvO2 values nor the mean response time (MRT; a weighted average of the time to 63% of the overall response) were altered by CHF (CON: 66.8 +/- 8.0, MOD: 72.4 +/- 11.8, SEV: 69.1 +/- 9.5 s). In marked contrast, SOL PmvO2, at recovery onset, was reduced significantly in the SEV group ( approximately 6 Torr) and PmvO2 MRT was slowed with increased severity of CHF (CON: 45.1 +/- 5.3, MOD: 63.2 +/- 9.4, SEV: 82.6 +/- 12.3 s; P < 0.05 CON vs. MOD and SEV). These data indicate that CHF slows PmvO2 recovery following contractions and lowers capillary O2 driving pressure in slow-twitch SOL, but not in fast-twitch PER muscle. These results may explain, in part, the slowed recovery kinetics (phosphocreatine and VO2) and pronounced fatigue following muscular work in CHF patients.
authors.affiliation: Departments of Anatomy, Physiology and Kinesiology, 129 Coles Hall, Kansas State University, Manhattan, KS 66506-5802, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: McDonough
authors.forename: Brad J
authors.initials: BJ
authors.lastname: Behnke
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Musch
authors.forename: David C
authors.initials: DC
authors.lastname: Poole
mesh_terms: D000818:Animals; D002908:Chronic Disease; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D008833:Microcirculation / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D010313:Partial Pressure; D010543:Peroneal Nerve / Q000502:physiology; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D010725:Phosphocreatine; D010100:Oxygen