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The 27.5 kD protein appears to control the oxidative phosphorylation in slow twitch muscle cells
THE EFFECT OF SOME NOVEL 1,4-DIHYDROPYRIDINES ON CA” DISTRIBUTION IN FROG SKELETAL MUSCLE N. Shvinka Lab, Inst. ofExp and Ciin Medicine, Riga. Latvia
THE EFFECTS OF SCIATIC NERVE SECTION ON THE CONTRACTION FORCE OF GASTROCNEMIUS MUSCLE IN CATS L. Plakane, P. Ozolins
Latvian institute of Experimental and Clinical Medicine, Riga, Latvia
The effects of I,4-dihydropyridines (DHP) ryodipine (R), cerebrocrast (C) and IOS-2069 were investigated on twitch muscle fibre segments, on isolated muscle fibres from m,i/eojb. and m.semifend as well as on msarrorius of Riemporaria and R.esculenfa. The technique using Sr2’ to extract the rapidly exchanging Ca” pool was employed. The agonist effect of substance IOS-2069 (5x lO.5 molil) on L-type Ca” channels was established. Maximum Isa increased by 35+3% (n=7). The threshold potential for activation of Is, was reduced by 20 mV. R (2x 1O-5mol/l) caused an inhibitory effect decreasing Ica through the L-type Ca” channels. R, C and IOS-2069 did not affect the inwardly rectifying K* channels of isolated muscle fibres. The effluxes of K’ and Rb’ from m.sartorius also remained unchanged after addition of 2x lO-4 molil R. Thus, the nonspecific DHP effects on ion transport in resting muscle seems to be poorly expressed. In m.sartorius R (2x10-4mol/l) significantly blocked the Sr” uptake without changes in Ca2’ and Mg2’ content. 108-2069 (2x IO4 mol/l) significantly increased the Sr” (by 20%) and Ca2’ (by 13%) contents in resting muscle, whereas Mg2‘ content remained unaffected. The [Sr2’] changes are interpreted as specific DHP-effect on the L-type Ca2’ channels in the muscle membrane. The ISO-2069-induced increase in Ca2’ content may result from competitive inhibition by Sr*’ of CaZa efflux via the Na+-Ca2’ exchange mechanism. We believe that the part of rapidly exchanging Ca2’ which corresponds to the IOS-2069-induced increment in Sr” content is localised inside the muscle fibre. DHPdependent [Ca”],. can play essential role in E-C coupling in skeletal muscle.
The
experiments were performed on anaesthetised cats gastrocnemiur muscles. Both muscles were stimulated directly through silver plate electrodes by brief trains (0.33 s) of rectangular-wave electrical impulses (0.1 ms, 100 Hz) once every 2 s. The muscles contracted in steady state conditions with force 25-30% of max contraction force. The svmnathetic was treated with ganglion _ biockator nervous system benzohexony (2.5%; 13.5-68.2 m&g) or P-blockator propranolol (0.5%; 2.2-15.5 mg/kg). Subsequent injection of 0.3 ml Novocain (2%) in the sciatic nerve after 30 min caused an increase of muscle contraction force (MCF) in 7 of 9 experiments by 26+4% (n=7). After section of sciatic nerve at the place of novocainization in the next 30 min the MCF further increased to 29*5% (n=5). The putting of a tourniquet on the thigh for 7 min (ischemic conditions) caused an transient increase of MCF by lOI* 1.4% (n=l7). This reaction appeared with 34k1.4 s latency and persisted for 7lk3.9 s (n=l7). The denervation of these muscles resulted in the increase of the reaction to the application of tourniquet: MCF rised by 180*3.7% (n=6); the duration of enhanced reaction was 182+19.2 sand the latent period was 144+21.4 s. Cardiac arrest by injection of air into thk v,jugularis induced a greater effect in denervated muscles (increase of MCF bv 169-205%.
duration 202-306 s) as compared to that in inehated muscles (increase of MCF II l-151%, duration 98-240 s). The fast elevated effect caused by denervation is thought to result from (i) recruitment of additional neiromotor units; (ii) the rise of adrenergetic chemosensitivity of extrajunctional area; (iii) additional loss of [Ca2’], from intracellular stores.
019 ELECTRICAL STIMULATION IN HUMAN PARALYZED MUSCLE M. Kjrer Sports Medicine Research Unit, Bispebjerg Hospital and Copenhagen Muscle Research Centre, University of Copenhagen, Denmark
THE 27.5 kD PROTEIN APPEARS TO CONTROL THE OXIDATIVE PHOSPHORYLATION IN SLOW TWITCH MUSCLE CELLS E K. Seppet,
L Kadaya.
N. Peet, T. Karimbre,
P Sikk,
and V. A Saks
Department of Pathophysiology, (Jniversrty of 7h-rtu, Laboratory OJ Hioenergetics, Instrtute of Chemrcal & Biological Physics, Tallinn. Gtonia
Paralyzed skeletal muscle due to spinal cord injury in humans results in atrophy, a fiber type shift towards type IIb/IIx, and low contents of glycolytic/oxidative enzymes, glucose transporting protein (GLUT4) and lactate transporters. Electrical stimulation of wrist extensor muscle improved local endurance, NMR determined PCr recovery (TX), and el-stim muscle strength. Long term (12 months) cycling training with electrical stimulation of the thigh muscle caused muscle fiber hypertrophy, musle fiber (MHC) shift towards type IIa, and improvement in insulin stimulated glucose uptake, tibia1 bone mineral content, markers of collagen type IV turnover and glycolytici oxidative enzymes in quadriceps muscle. Intense el-stim of the tibialis anterior muscle over 9 weeks with low frequency resulted in a slower contracting more fatigue resistant muscle and may precede a fast-to-slow shift in MHC expression. Electrical stimulation of human paralyzed muscle partially reverses inactivity associated changes occuring in spinal cord individuals.
Analysis of the the kinetics of m situ regulation of mitochondrial respiration by ADP in saponin-skinned muscle fibers from rat heart and m. soleus has revealed the apparent Km for ADP in a range of 200-350 vM. In the presence of creatine (20 mM) or after treatment with trypsin the Km for ADP decreases to the values characteristic of the isolated mitochondria from the same types of muscles (lo-20 PM). These results show that in slow twitch muscles the permeability of outer mitochondrial membrane for ADP is low and controlled by a trypsin-sensitive cytoplasmic protein Electrophoretic analysis revealed one of the possible candidates for such a protein in the heart It has the MW of 27 5 kD, starts to be expressed after I week post partum and reaches its adult levels by 3 weeks of postnatal development. Expression of that protein correlates with an increase in Km for ADP from 64% 6 to 226+17 pM
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THE EFFECTS OF SCIATIC NERVE SECTION ON THE CONTRACTION FORCE OF GASTROCNEMIUS MUSCLE IN CATS L. Plakane, P. Ozolins
Latvian institute of Experimental and Clinical Medicine, Riga, Latvia
The effects of I,4-dihydropyridines (DHP) ryodipine (R), cerebrocrast (C) and IOS-2069 were investigated on twitch muscle fibre segments, on isolated muscle fibres from m,i/eojb. and m.semifend as well as on msarrorius of Riemporaria and R.esculenfa. The technique using Sr2’ to extract the rapidly exchanging Ca” pool was employed. The agonist effect of substance IOS-2069 (5x lO.5 molil) on L-type Ca” channels was established. Maximum Isa increased by 35+3% (n=7). The threshold potential for activation of Is, was reduced by 20 mV. R (2x 1O-5mol/l) caused an inhibitory effect decreasing Ica through the L-type Ca” channels. R, C and IOS-2069 did not affect the inwardly rectifying K* channels of isolated muscle fibres. The effluxes of K’ and Rb’ from m.sartorius also remained unchanged after addition of 2x lO-4 molil R. Thus, the nonspecific DHP effects on ion transport in resting muscle seems to be poorly expressed. In m.sartorius R (2x10-4mol/l) significantly blocked the Sr” uptake without changes in Ca2’ and Mg2’ content. 108-2069 (2x IO4 mol/l) significantly increased the Sr” (by 20%) and Ca2’ (by 13%) contents in resting muscle, whereas Mg2‘ content remained unaffected. The [Sr2’] changes are interpreted as specific DHP-effect on the L-type Ca2’ channels in the muscle membrane. The ISO-2069-induced increase in Ca2’ content may result from competitive inhibition by Sr*’ of CaZa efflux via the Na+-Ca2’ exchange mechanism. We believe that the part of rapidly exchanging Ca2’ which corresponds to the IOS-2069-induced increment in Sr” content is localised inside the muscle fibre. DHPdependent [Ca”],. can play essential role in E-C coupling in skeletal muscle.
The
experiments were performed on anaesthetised cats gastrocnemiur muscles. Both muscles were stimulated directly through silver plate electrodes by brief trains (0.33 s) of rectangular-wave electrical impulses (0.1 ms, 100 Hz) once every 2 s. The muscles contracted in steady state conditions with force 25-30% of max contraction force. The svmnathetic was treated with ganglion _ biockator nervous system benzohexony (2.5%; 13.5-68.2 m&g) or P-blockator propranolol (0.5%; 2.2-15.5 mg/kg). Subsequent injection of 0.3 ml Novocain (2%) in the sciatic nerve after 30 min caused an increase of muscle contraction force (MCF) in 7 of 9 experiments by 26+4% (n=7). After section of sciatic nerve at the place of novocainization in the next 30 min the MCF further increased to 29*5% (n=5). The putting of a tourniquet on the thigh for 7 min (ischemic conditions) caused an transient increase of MCF by lOI* 1.4% (n=l7). This reaction appeared with 34k1.4 s latency and persisted for 7lk3.9 s (n=l7). The denervation of these muscles resulted in the increase of the reaction to the application of tourniquet: MCF rised by 180*3.7% (n=6); the duration of enhanced reaction was 182+19.2 sand the latent period was 144+21.4 s. Cardiac arrest by injection of air into thk v,jugularis induced a greater effect in denervated muscles (increase of MCF bv 169-205%.
duration 202-306 s) as compared to that in inehated muscles (increase of MCF II l-151%, duration 98-240 s). The fast elevated effect caused by denervation is thought to result from (i) recruitment of additional neiromotor units; (ii) the rise of adrenergetic chemosensitivity of extrajunctional area; (iii) additional loss of [Ca2’], from intracellular stores.
019 ELECTRICAL STIMULATION IN HUMAN PARALYZED MUSCLE M. Kjrer Sports Medicine Research Unit, Bispebjerg Hospital and Copenhagen Muscle Research Centre, University of Copenhagen, Denmark
THE 27.5 kD PROTEIN APPEARS TO CONTROL THE OXIDATIVE PHOSPHORYLATION IN SLOW TWITCH MUSCLE CELLS E K. Seppet,
L Kadaya.
N. Peet, T. Karimbre,
P Sikk,
and V. A Saks
Department of Pathophysiology, (Jniversrty of 7h-rtu, Laboratory OJ Hioenergetics, Instrtute of Chemrcal & Biological Physics, Tallinn. Gtonia
Paralyzed skeletal muscle due to spinal cord injury in humans results in atrophy, a fiber type shift towards type IIb/IIx, and low contents of glycolytic/oxidative enzymes, glucose transporting protein (GLUT4) and lactate transporters. Electrical stimulation of wrist extensor muscle improved local endurance, NMR determined PCr recovery (TX), and el-stim muscle strength. Long term (12 months) cycling training with electrical stimulation of the thigh muscle caused muscle fiber hypertrophy, musle fiber (MHC) shift towards type IIa, and improvement in insulin stimulated glucose uptake, tibia1 bone mineral content, markers of collagen type IV turnover and glycolytici oxidative enzymes in quadriceps muscle. Intense el-stim of the tibialis anterior muscle over 9 weeks with low frequency resulted in a slower contracting more fatigue resistant muscle and may precede a fast-to-slow shift in MHC expression. Electrical stimulation of human paralyzed muscle partially reverses inactivity associated changes occuring in spinal cord individuals.
Analysis of the the kinetics of m situ regulation of mitochondrial respiration by ADP in saponin-skinned muscle fibers from rat heart and m. soleus has revealed the apparent Km for ADP in a range of 200-350 vM. In the presence of creatine (20 mM) or after treatment with trypsin the Km for ADP decreases to the values characteristic of the isolated mitochondria from the same types of muscles (lo-20 PM). These results show that in slow twitch muscles the permeability of outer mitochondrial membrane for ADP is low and controlled by a trypsin-sensitive cytoplasmic protein Electrophoretic analysis revealed one of the possible candidates for such a protein in the heart It has the MW of 27 5 kD, starts to be expressed after I week post partum and reaches its adult levels by 3 weeks of postnatal development. Expression of that protein correlates with an increase in Km for ADP from 64% 6 to 226+17 pM
121