Heat production in chemically skinned smooth muscle of guinea‐pig taenia coli.

Lönnbro, Per; Hellstrand, Per

doi:10.1113/jphysiol.1991.sp018714

Cited by 16 publications

(5 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…More extensive treatment with Triton X-100 could reduce this activity further (Trinkle-Mulcahy et al, 1994, see above), but at the expense of reduced force-bearing capacity of the smooth muscle associated with loss of myosin (data not shown). Mitochondrial and ion-transporting ATPase activities are below detection levels in permeabilized smooth muscle (Lönnbro and Hellstrand, 1991), but, unfortunately, regardless of the method used, whether coupled NADH assay, HPLC of nucleotides, or heat measurements, accurate estimates of basal myosin ATPase activity in permeabilized smooth muscle are limited by the ecto-ATPase (Trinkle-Mulcahy et al, 1994; present study).…”

Section: Discussionmentioning

confidence: 71%

Time-Resolved Measurements of Phosphate Release by Cycling Cross-Bridges in Portal Vein Smooth Muscle

He¹,

Ferenczi²,

Brüne³

et al. 1998

Biophysical Journal

View full text Add to dashboard Cite

The rate of release of inorganic phosphate (Pi) from cycling cross-bridges in rabbit portal-anterior mesenteric vein smooth muscle was determined by following the fluorescence of the Pi-reporter, MDCC-PBP (Brune, M., J. L. Hunter, S. A. Howell, S. R. Martin, T. L. Hazlett, J. E. T. Corrie, and M. R. Webb. 1998. Biochemistry. 37:10370-10380). Cross-bridge cycling was initiated by photolytic release of ATP from caged-ATP in Triton-permeabilized smooth muscles in rigor. When the regulatory myosin light chains (MLC20) had been thiophosphorylated, the rate of Pi release was biphasic with an initial rate of 80 microM s-1 and amplitude 108 microM, decreasing to 13.7 microM s-1. These rates correspond to fast and slow turnovers of 1.8 s-1 and 0.3 s-1, assuming 84% thiophosphorylation of 52 microM myosin heads. Activation by Ca2+-dependent phosphorylation subsequent to ATP release resulted in slower Pi release, paralleling the rate of contraction that was also slower than after thiophosphorylation, and was also biphasic: 51 microM s-1 and 13.2 microM s-1. These rates suggest that the activity of myosin light chain kinase and phosphatase ("pseudo-ATPase") contributes <20% of the ATP usage during cross-bridge cycling. The extracellular "ecto-nucleotidase" activity was reduced eightfold by permeabilization, conditions in which the ecto-ADPase was 17% of the ecto-ATPase. Nevertheless, the remaining ecto-ATPase activity reduced the precision of the estimate of cross-bridge ATPase. We conclude that the transition from fast to slow ATPase rates reflects the properties and forces directly acting on cross-bridges, rather than the result of a time-dependent decrease in activation (MLC20 phosphorylation) occurring in intact smooth muscle. The mechanisms of slowing may include the effect of positive strain on cross-bridges, inhibition of the cycling rate by high affinity Mg-ADP binding, and associated state hydrolysis.

show abstract

Section: Discussionmentioning

confidence: 71%

Time-Resolved Measurements of Phosphate Release by Cycling Cross-Bridges in Portal Vein Smooth Muscle

He¹,

Ferenczi²,

Brüne³

et al. 1998

Biophysical Journal

View full text Add to dashboard Cite

show abstract

“…A disproportional rise in J02 at the highest force-generating levels can be seen in several previous studies (Arner & Hellstrand, 1983;Siegman, Canine semitendinosus -=. & Mooers, 1985;Krisanda & Paul, 1988;Lonnbro & Hellstrand, 1991) (Fig. 2B).…”

Section: Discussionmentioning

confidence: 84%

“…The basal rate of ATP consumption in the swine carotid media is about half that of striated muscle and approximately doubles under conditions of nearmaximal contraction ( Fig. 4; Gibbs, 1983;Kushmerick, 1983;Krisanda & Paul, 1988;Lonnbro & Hellstrand, 1991). The energy cost of isometric contractions in a latch state is extremely low compared with that in striated muscles (Fig.…”

Section: Discussionmentioning

confidence: 99%

Dependence of ATP consumption on cross‐bridge phosphorylation in swine carotid smooth muscle.

Wingard

Rutgeerts

Murphy

1994

The Journal of Physiology

View full text Add to dashboard Cite

1. Ca2+-dependent phosphorylation of the myosin regulatory light chain (MRLC) initiates cross-bridge cycling and contraction in smooth muscle. A four-state cross-bridge model, in which Ca2+-dependent phosphorylation is the only proposed regulatory mechanism, can predict the mechanical output of the swine carotid media. Our aims were to determine whether ATP consumption rates and the economy of force maintenance are regulated functions of MRLC phosphorylation as predicted by the model. 2. Steady-state force and oxygen consumption were measured in medial rings of swine carotid arteries activated with depolarizing solutions and agents capable of maintaining a wide range of steady-state myoplasmic Ca2+ and MRLC phosphorylation levels. 3. Suprabasal ATP consumption increased almost linearly with MRLC phosphorylation and exhibited a hyperbolic increase with active stress, as predicted. 4. The economy of stress maintenance fell with increases in suprabasal phosphorylation. 5. In absolute terms the energetic cost of covalent regulation by cross-bridge phosphorylation was small, although it may be a significant fraction of the ATP consumption associated with contraction.Recognition that some vascular smooth muscles can maintain force with ATP consumption rates more than 300-fold lower than vertebrate striated muscle is almost a century old (Paul, 1980(Paul, , 1983. Nevertheless, insights into how smooth muscle accomplishes this with the same molecular motor as striated muscle that involves cyclical interactions between the myosin cross-bridges and actin in the thin filaments is quite recent. Two differences between striated and smooth muscles affecting ATP consumption are (i) the expression of myosin isoforms with intrinsically slow turnover rates, and (ii) the presence of a covalent regulatory mechanism determining cross-bridge attachment and cycling in smooth muscle.Regulation involves Ca2+-dependent phosphorylation of the myosin regulatory light chains (MRLC) by myosin light chain kinase (MLCK) and subsequent dephosphorylation by myosin light chain phosphatase (MLCP) (Paul, 1987;Hartshorne, 1987;Murphy, 1994). Assuming that both free and attached cross-bridges may serve as substrates for MLCK and MLCP, covalent regulation of cross-bridges allows for both free and attached cross-bridges to be phosphorylated or dephosphorylated, yielding four crossbridge states (Fig. 1A) (Murphy, 1994).The four-state cross-bridge model suffices to explain the relationships between force, shortening velocity and MRLC phosphorylation in the swine carotid media stimulated by depolarization, neurotransmitters or hormones (Hai & Murphy, 1988a, b). The model predicts a hyperbolic dependence of stress on MRLC phosphorylation, where the stress generation is attributed to two forcegenerating cross-bridge states: a phosphorylated slowly cycling state (AMp) and an even slower cycle, described by the enzymatic rate constants of the model k1, k3, k5 and k7, incorporating an unphosphorylated 'latch-bridge' state (AM) (Fig. 1A). When Ca2+ and MRLC pho...

show abstract

“…In this case the muscle was attached to a modified stirrer that was placed in a 4 mL stainless steel ampoule containing 2.7 mL of relaxant solution. The muscle contractions were induced by adding calcium chloride into the solution using the perfusion or titration unit to which the stirrer was attached [ 62 ]. In their synchronized parallel experiment the authors showed that the muscle contraction and work measured using a force transducer were in perfect agreement with heat production rate (heat-flow) measured by the microcalorimeter ( Figure 4 ).…”

Section: Biomedical Applications Of Imcmentioning

confidence: 99%

“…Numbers under backets indicate the calcium concentration added in μM. Figure modified from [ 62 ] with permission of John Wiley & Sons Ltd.…”

Section: Figurementioning

confidence: 99%

Biomedical Use of Isothermal Microcalorimeters

Braissant

Wirz

Göpfert

et al. 2010

Sensors

View full text Add to dashboard Cite

Isothermal microcalorimetry is becoming widely used for monitoring biological activities in vitro. Microcalorimeters are now able to measure heat production rates of less than a microwatt. As a result, metabolism and growth of relatively small numbers of cultured bacteria, protozoans, human cells and even small animals can be monitored continuously and extremely accurately at any chosen temperature. Dynamic effects on these organisms of changes in the culture environment—or of additions to it—are easily assessed over periods from hours to days. In addition microcalorimetry is a non-destructive method that does not require much sample preparation. It is also completely passive and thus allows subsequent evaluations of any kind on the undisturbed sample. In this review, we present a basic description of current microcalorimetry instruments and an overview of their use for various biomedical applications. These include detecting infections, evaluating effects of pharmaceutical or antimicrobial agents on cells, monitoring growth of cells harvested for tissue eingineering, and assessing medical and surgical device material physico-chemical stability and cellular biocompatibility.

show abstract

Heat production in chemically skinned smooth muscle of guinea‐pig taenia coli.

Cited by 16 publications

References 31 publications

Time-Resolved Measurements of Phosphate Release by Cycling Cross-Bridges in Portal Vein Smooth Muscle

Time-Resolved Measurements of Phosphate Release by Cycling Cross-Bridges in Portal Vein Smooth Muscle

Dependence of ATP consumption on cross‐bridge phosphorylation in swine carotid smooth muscle.

Biomedical Use of Isothermal Microcalorimeters

Contact Info

Product

Resources

About