Title page for ETD etd-582914849741271


Type of Document Dissertation
Author Spangenburg, Espen E.
Author's Email Address espangen@vt.edu
URN etd-582914849741271
Title The Effects of Lactate on Whole Muscle Function and Sarcoplasmic Reticulum Function
Degree Master of Science
Department Human Nutrition, Foods, and Exercise
Advisory Committee
Advisor Name Title
Moore, David
Ward, Christopher W.
Williams, Jay H. Committee Chair
Keywords
  • sarcoplasmic retciulum
  • fatigue
  • calcium
  • muscle
  • lactate
Date of Defense 1997-04-24
Availability unrestricted
Abstract

Numerous studies have attributed the decrease in force

production of skeletal muscle during exercise to a increase

in lactate concentration ([lactate]). This notion is based on

the high negative correlation between plasma lactate and

force during fatigue and recovery. These experiments

attempted to determine if lactate directly effects force

production in skeletal muscle. Mouse extensor digitorum

longus muscles (EDL) were isolated and incubated in a

buffered Ringers solution at a pH 7.2 and exposed at three

minute intervals to a final concentration of 10, 20, 30,

50mM lactate. At 21° C, tetanic force production (Po,

250ms, 110Hz) decreased to 99.3 ± 1.0, 97.1 ± 1.2,

94.9 ± 1.1* and 93.1 ± 1.3*% of initial and the rate of

force development (+dP/dt) was reduced to 99.4 ± 0.7,

96.8 ± 0.5, 93.5 ± 0.6*, and 89.3 ± 1.2*% of initial

(*p<0.05 vs untreated muscles). At 37° C the effects of

lactate were augmented. Po was reduced to 89.7 ± 1.1,

81.0 ± 2.4, 73 ± 3.9*, and 61.6 ± 5.4*% and +dP/dt

was reduced to 79.4 ± 1.8*, 65.9 ± 2.8*, 55.4 ± 4.0*,

and 44.3 ± 5.0*% of initial (*p<0.05 vs control muscles).

The next phase was to determine if the changes in Po and

+dP/dt were due to alterations in the sacroplasmic

reticulum (SR) Ca2+ exchange. The SR of EDL

homogenates were actively loaded with Ca2+ and release

was initiated by 25 mM AgNO3. The rate of Ca2+

release was significantly reduced by 31% (2.48 ± 1.21 vs

1.72 ± 0.24 mmol·mg-1·min-1) in the presence of 25 mM

lactate. These results indicate that exposure to increased

[lactate], independent of the H+, decreases force

production of whole muscle, effects that are greater at 37°

C than 21° C. Also increased lactate reduces the rate of

SR Ca2+ release. These results suggest that lactate

depresses whole muscle force production by altering

Ca2+ release of the SR. They also support the idea that

increased lactate concentrations disrupt normal muscle

function leading to the development of fatigue.

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