In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 98, No. 10 ( 2001-05-08), p. 5904-5909
Abstract:
We have used a fluorescence recovery after photobleaching
(FRAP) technique to measure radial diffusion of myoglobin and other proteins in single skeletal and cardiac muscle cells. We compare the
radial diffusivities, D r (i.e., diffusion
perpendicular to the long fiber axis), with longitudinal ones, D l (i.e., parallel to the long fiber axis),
both measured by the same technique, for myoglobin (17 kDa), lactalbumin (14 kDa), and ovalbumin (45 kDa). At 22°C, D l for myoglobin is 1.2 ×
10 −7 cm 2 /s in soleus fibers
and 1.1 × 10 −7 cm 2 /s
in cardiomyocytes. D l for lactalbumin is
similar in both cell types. D r for myoglobin
is 1.2 × 10 −7 cm 2 /s in
soleus fibers and 1.1 × 10 −7 cm 2 /s in cardiomyocytes and, again,
similar for lactalbumin. D l and D r for ovalbumin are 0.5 ×
10 −7 cm 2 /s. In the case of
myoglobin, both D l and D r at 37°C are about 80% higher than at
22°C. We conclude that intracellular diffusivity of myoglobin and other proteins ( i ) is very low in striated muscle cells,
≈1/10 of the value in dilute protein solution, ( ii )
is not markedly different in longitudinal and radial direction, and ( iii ) is identical in heart and skeletal muscle. A Krogh
cylinder model calculation holding for steady-state tissue oxygenation predicts that, based on these myoglobin diffusivities,
myoglobin-facilitated oxygen diffusion contributes 4% to the overall intracellular oxygen transport of maximally exercising skeletal muscle
and less than 2% to that of heart under conditions of high work load.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.101109798
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2001
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
