Faculty Collaboration Database

Substrate profile in rat soleus muscle fibers after hindlimb unloading and fatigue. J Appl Physiol (1985) 2000 Feb;88(2):473-8

Date

02/05/2000

Pubmed ID

10658013

DOI

10.1152/jappl.2000.88.2.473

Scopus ID

2-s2.0-0033977433 (requires institutional sign-in at Scopus site)   64 Citations

Abstract

Limb muscles from rats flown in space and after hindlimb unloading (HU) show an increased fatigability, and spaceflight has been shown to result in a reduced ability to oxidize fatty acids. The purpose of this investigation was to determine the effects of HU on the substrate content in fast- and slow-twitch fibers and to assess the substrate utilization patterns in single slow type I fibers isolated from control and HU animals. A second objective was to assess whether HU altered the ability of the heart or limb muscle to oxidize pyruvate or palmitate. After 2 wk of HU, single fibers were isolated from the freeze-dried soleus and gastrocnemius muscles. HU increased the glycogen content in all fiber types, and it increased lactate, ATP, and phosphocreatine in the slow type I fiber. After HU, the type I fiber substrate profile was shifted toward that observed in fast fibers. For example, fiber glycogen increased from 179 +/- 16 to 285 +/- 25 mmol/kg dry wt, which approached the 308 +/- 23 mmol/kg dry wt content observed in the post-HU type IIa fiber. With contractile activity, the type I fiber from the HU animal showed a greater utilization of glycogen and accumulation of lactate compared with the control type I fiber. HU had no effect on the ability of crude homogenate or mitochondria fractions from the soleus or gastrocnemius to oxidize pyruvate or palmitate. The increased fatigability after HU may have resulted from an elevated glycolysis producing an increased cell lactate and a decreased pH.

Author List

Grichko VP, Heywood-Cooksey A, Kidd KR, Fitts RH

Author

Robert Fitts PhD Professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphate
Animals
Glycogen
Hindlimb Suspension
Lactic Acid
Male
Muscle Fatigue
Muscle Fibers, Fast-Twitch
Muscle Fibers, Slow-Twitch
Muscle, Skeletal
Oxidation-Reduction
Palmitates
Phosphocreatine
Pyruvic Acid
Rats
Rats, Sprague-Dawley