Diffusion coefficients of atp and creatine phosphate in isolated muscle: pulsed gradient <sup>31</sup>p nmr of small biological samples

Hubley, Mark J.; Moerland, Timothy S.; Rosanske, Richard

doi:10.1002/nbm.1940080205

Cited by 71 publications

(60 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Anisotropy of sarcoplasmic diffusion has been reported for small molecules; for Ca 2ϩ (7), O 2 (8), and H 2 O (6), diffusion in radial direction is believed to be slower than along the longitudinal fiber axis. An anisotropy of sarcoplasmic D also appeared very likely for ATP and phosphocreatine (26). This phenomenon was attributed to a greater tortuosity effect exerted by the myofilamental lattice in radial direction.…”

Section: Discussion Translational Diffusion Of Mb and Of Other Proteimentioning

confidence: 92%

Radial and longitudinal diffusion of myoglobin in single living heart and skeletal muscle cells

Papadopoulos

Endeward

Revesz-Walker

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

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, Dr (i.e., diffusion perpendicular to the long fiber axis), with longitudinal ones, Dl (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. Dl for lactalbumin is similar in both cell types. Dr 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. Dl and Dr for ovalbumin are 0.5 ؋ 10 ؊7 cm 2 ͞s. In the case of myoglobin, both Dl and Dr 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, Ϸ1͞10 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. Since Wittenberg (1, 2) demonstrated that myoglobin (Mb) diffusion facilitates O 2 transport in aqueous solutions, it has been postulated that facilitated O 2 diffusion may play an important role in respiring muscle. The extent of Mb-facilitated sarcoplasmic O 2 transport will depend mainly on the intracellular concentration of Mb, which is fairly well known for various muscle fiber types, and on the magnitude of its sarcoplasmic diffusion coefficient (D), which still is a matter of discussion. The direct measurement of translational Mb diffusivity in living skeletal muscle fibers (3-5) revealed an unexpectedly small value for D. However, in these studies, Mb diffusivity-for technical reasons-has been measured only along the longitudinal axis of muscle fibers and over long distances (tens or hundreds of sarcomere lengths). In contrast, facilitated O 2 transport in vivo mainly requires radial diffusion of Mb, from the sarcolemma to the mitochondria, i.e., in the direction perpendicular to the longitudinal fiber axis. It is conceivable that the highly ordered sarcoplasmic structures, e.g., the myofilaments, might give rise to significant differences between longitudinal (D l ) and radial (D r ) diffusion coefficients. Such an anisotropy has been reported for small molecules such as H 2 O (6), Ca 2ϩ (7), and O 2 (8), but it was not clear whether this also would be true for protein diffusion. Thus, the magnitude of D r in living heart and skeletal muscle remained a matter of speculation. For example, Baylor and Pape (3) argued that the...

show abstract

Section: Discussion Translational Diffusion Of Mb and Of Other Proteimentioning

confidence: 92%

Radial and longitudinal diffusion of myoglobin in single living heart and skeletal muscle cells

Papadopoulos

Endeward

Revesz-Walker

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…This environment has a high total protein concentration, an extended network of myofilaments and a substantial volume fraction (up to 40% in cardiomyocytes) occupied by mitochondria, sarcoplasmic reticulum and T tubules (Eisenberg, 1983). All of these might present major obstacles to protein diffusion For small molecules such as O 2 , CO 2 , ATP and PCr, diffusion in the sarcoplasm is reduced by only 20-35% compared with diffusion in water (Kawashiro et al, 1975;Hubley et al, 1995). So the 'microviscosity' experienced by small molecules inside muscle cells is rather close to the viscosity of water.…”

Section: Insights Into Cytoplasmic Microviscosity and Architecture Frmentioning

confidence: 99%

Myoglobin's old and new clothes: from molecular structure to function in living cells

Gros

Wittenberg

Jue

2010

Journal of Experimental Biology

102

View full text Add to dashboard Cite

SUMMARY Myoglobin, a mobile carrier of oxygen, is without a doubt an important player central to the physiological function of heart and skeletal muscle. Recently, researchers have surmounted technical challenges to measure Mb diffusion in the living cell. Their observations have stimulated a discussion about the relative contribution made by Mb-facilitated diffusion to the total oxygen flux. The calculation of the relative contribution, however, depends upon assumptions, the cell model and cell architecture, cell bioenergetics, oxygen supply and demand. The analysis suggests that important differences can be observed whether steady-state or transient conditions are considered. This article reviews the current evidence underlying the evaluation of the biophysical parameters of myoglobin-facilitated oxygen diffusion in cells, specifically the intracellular concentration of myoglobin, the intracellular diffusion coefficient of myoglobin and the intracellular myoglobin oxygen saturation. The review considers the role of myoglobin in oxygen transport in vertebrate heart and skeletal muscle, in the diving seal during apnea as well as the role of the analogous leghemoglobin of plants. The possible role of myoglobin in intracellular fatty acid transport is addressed. Finally, the recent measurements of myoglobin diffusion inside muscle cells are discussed in terms of their implications for cytoarchitecture and microviscosity in these cells and the identification of intracellular impediments to the diffusion of proteins inside cells. The recent experimental data then help to refine our understanding of Mb function and establish a basis for future investigation.

show abstract

“…Because diffusion measurements are also possible with MR techniques that employ diffusion magnetic field gradients (41), noninvasive studies of metabolite diffusion are feasible, although they have been limited. Indeed, combining 31 P-MRS with diffusion MR methodology has provided measures of D PCr in excised strips of fish (19,20,24) and frog muscle (49,50) and in the limbs of rats and rabbits (9,32,43). The average diffusion of PCr and Cr has also been measured by 1 H-MRS in isolated rat hearts (28).…”

mentioning

confidence: 99%

High-energy phosphate transfer in human muscle: diffusion of phosphocreatine

Gabr¹,

El-Sharkawy²,

Schär

et al. 2011

American Journal of Physiology-Cell Physiology

View full text Add to dashboard Cite

The creatine kinase (CK) reaction is central to muscle energetics, buffering ATP levels during periods of intense activity via consumption of phosphocreatine (PCr). PCr is believed to serve as a spatial shuttle of high-energy phosphate between sites of energy production in the mitochondria and sites of energy utilization in the myofibrils via diffusion. Knowledge of the diffusion coefficient of PCr (D PCr) is thus critical for modeling and understanding energy transport in the myocyte, but DPCr has not been measured in humans. Using localized phosphorus magnetic resonance spectroscopy, we measured D PCr in the calf muscle of 11 adults as a function of direction and diffusion time. The results show that the diffusion of PCr is anisotropic, with significantly higher diffusion along the muscle fibers, and that the diffusion of PCr is restricted to a ϳ28-m pathlength assuming a cylindrical model, with an unbounded diffusion coefficient of ϳ0.69 ϫ 10 Ϫ3 mm 2 /s. This distance is comparable in size to the myofiber radius. On the basis of prior measures of CK reaction kinetics in human muscle, the expected diffusion distance of PCr during its half-life in the CK reaction is ϳ66 m. This distance is much greater than the average distances between mitochondria and myofibrils. Thus these first measurements of PCr diffusion in human muscle in vivo support the view that PCr diffusion is not a factor limiting high-energy phosphate transport between the mitochondria and the myofibrils in healthy resting myocytes. myocyte; energy metabolism; creatine kinase shuttle; human studies PHOSPHOCREATINE (PCr) serves as the main short-term energy reserve in muscle, heart, and brain. PCr generates ATP to fuel cellular processes, including ion transport and muscular contraction, via the creatine kinase (CK) reaction. The CK reaction reversibly transfers a phosphoryl group between PCr and ATP, with unphosphorylated Cr and ADP as the other reactants and k as the forward pseudo-first-order rate constant of the reaction: PCr ϩ ADP ϩ H ϩ ↔ k ATP ϩ Cr . It was long ago hypothesized that the CK reaction serves as an intracellular energy shuttle, facilitating the transfer of high-energy phosphate from sites of de novo ATP creation in the mitochondria to sites of energy utilization, such as the myofibrils (4, 29, 45). The energy transfer mechanism in this PCr shuttle hypothesis involves 1) the creation of PCr at the mitochondria from the reverse CK reaction, 2) the diffusion of PCr to the point of use (including possible recycling through CK in the cytosol), and 3) the regeneration of ATP from ADP and PCr via the forward CK reaction to supply the needed energy (Fig. 1). Provided that the rate of ATP production via CK is manyfold higher than that generated by oxidative phosphorylation, the CK reaction could serve as a temporal-spatial energy buffer, supplying ATP when and where it is needed during periods of acute demand and/or stress.Since PCr diffusion is central to the PCr shuttle hypothesis, knowledge of its diffusion coefficient (D PCr ) is ...

show abstract

Diffusion coefficients of atp and creatine phosphate in isolated muscle: pulsed gradient ³¹p nmr of small biological samples

Cited by 71 publications

References 25 publications

Radial and longitudinal diffusion of myoglobin in single living heart and skeletal muscle cells

Radial and longitudinal diffusion of myoglobin in single living heart and skeletal muscle cells

Myoglobin's old and new clothes: from molecular structure to function in living cells

High-energy phosphate transfer in human muscle: diffusion of phosphocreatine

Contact Info

Product

Resources

About

Diffusion coefficients of atp and creatine phosphate in isolated muscle: pulsed gradient 31p nmr of small biological samples

Cited by 71 publications

References 25 publications

Radial and longitudinal diffusion of myoglobin in single living heart and skeletal muscle cells

Radial and longitudinal diffusion of myoglobin in single living heart and skeletal muscle cells

Myoglobin's old and new clothes: from molecular structure to function in living cells

High-energy phosphate transfer in human muscle: diffusion of phosphocreatine

Contact Info

Product

Resources

About

Diffusion coefficients of atp and creatine phosphate in isolated muscle: pulsed gradient ³¹p nmr of small biological samples