Effect of acidosis on control of respiration in skeletal
muscle.
Harkema, Susan J., and Ronald A. Meyer.
Depts. of Physiology and Radiology, Michigan State University, East
Lansing, MI 48824
APStracts 3:0322C, 1996.
The relationships between oxygen consumption (QO2) vs. calculated
cytoplasmic [ADP] and the free energy of ATP hydrolysis (GATP) were
examined in ex vivo, arterially-perfused cat soleus muscles during
repetitive twitch stimulation under normocapnic (5%CO2) and
hypercapnic (70%CO2) conditions. Hypercapnia decreased extra- and
intra-cellular pH by over 0.5, but had no significant effect on QO2
or PCr/ATP in muscles at rest. The maximum QO2 measured during
stimulation, and the rate constant for PCr recovery after
stimulation, both decreased during hypercapnic compared to
normocapnic perfusion, but the estimated ATP/O2 ratio was unchanged.
The change in PCr and GATP with increasing QO2 was greater during
hypercapnic compared to normocapnic stimulation, as expected from the
decrease in maximum QO2. However, the relationships between QO2 vs.
[ADP] and GATP were both shifted to the left during hypercapnia
compared to normocapnia. The results show that changes in cytoplasmic
adenine nucleotides and phosphate are not sufficient to explain the
control of respiration in skeletal muscle. However, in the context of
thermodynamic models of respiratory control, the results can be
explained by increased intramitochondrial potential for ATP synthesis
at low pH.
Received 1 March 1996; accepted in final form 30 August 1996.
APS Manuscript Number C116-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996