- Email: [email protected]
Human variation in the metabolic profile and contractile properties of skeletal latissimus dorsi muscle (LDM)
J Mol
Cell
Cardiol
PI14
EFFECT OF THE NTCB, N-TERMINAL FRAGMENT OF CALDESMON ON MYOSIN ASSOCIATION WITH THE TRITON-INSOLUBLe CYTOSRELETON OF PLATELETS. Department of Physiology & Biophysics, University of M.E. Hemric and J.R. Haeberle. Vermont, Burlington, VT 05405 USA we have previously shown that a smooth and Using an in vitro motility assay, promotes actomyosin interaction and crossbridge nonmuscle protein, caldesmon, cycling at near physiological ionic strengths (Hemric, M.E. and Haeberle, J.R. We showed that this promotion was due to the formation (1992) Biophys. J. 61, A6). of actin-caldesmon-myosin complexes by using the NTCB, myosin-binding fragment of Now we have investigated caldesmon as a competitive inhibitor of complex formation. whether actin-caldesmon-myosin complexes promote actomyosin interaction in viva, The association of myosin with using platelet activation as an experimental model. a Triton-insoluble cytoskeleton increases during platelet activation and was attributed to light chain phosphorylation (Fox, J.E.B. and Phillips, D.R. (1982) J. Biol. Chem. 257, 4120-4126). We have reproduced these cytoskeletal changes and have used the NTCB, myosin-binding fragment of caldesmon to investigate whether actincaldesmon-myosin complexes are involved in this promotion of actomyosin interaction. Myosin association with the Triton-insoluble cytoskeleton was competitively These results suggest that myosininhibited by the myosin-binding fragment. caldesmon-actin complexes occur in viva and are involved in the association of myosin with the Triton-insoluble cytoskeleton during platelet activation.
PI15
STIMULATION BATE DEPENDENT ATTENUATION OF PHARMACOLOGICALLY INCREASED EFFECTIVE REFRACTORY PERIOD. Paul &miff, Maurice Briggs, Alan Ezrin, Cardiovss. Pharm., Sterling Winthrop PRD, Rensselaer NY, 12144. The effectiveness (increased effective refractory period, ERP) of most antiarrhythmics is attenuated as heart rate is increased. This study determines the relationship of drug increased ERP and rate dependent attenuation of ERP. The rate dependent effects of Disopyramide (DIS), Flecainide (FLC), Sematilide (SEM), Dofetilide @OF) and Sotalol (SOT) on El@ were evaluated in a rabbit heart Langendorff model. FXP was determined pre- and post- drug (15 min. exposure) at four rates 1210, 150, 180, and 220 stim / min. The ERP determined pre-drug at each stimulation rate was subtracted from ERP determined after each drug concentration (A ERP). A ERP increases of 20 msec or more were considered
24 (Supplement
physiologically
III)
significant.
(1992)
DIS
10 & 30 FM,
FLC
1 & 3 FM,
SEM
10 & 30 PM,
DOF
0.003, 0.01 & 0.03 PM and SOT 10, 30 & 100 PM had similar responses. The rate dependent attenuation of A m was greater with increased initial A ERP. The slopes of the A ERP vs rate relationship were significantly different from zero indicating that A ERP decreased as heart rate increased. The A ERP vs rate slopes were regressed against the A ERP at 120 stimlmin (r= .872, n=50, m=-0.005, b=O.O23) which defmes the “normal” attenuation relationship. Drugs which have responses positive to the 95 % confidence interval for this relationship would be less attenuated by rate. The relationship for SOT was positive while the other tested agents were not different from the “normal” relationship. This analysis allows drugs to be identified which are less attenuated by increased heart rate.
/‘I16
HUMAN VARIATION IN THE METABOLIC PROFILE AND CONTRACTILE PROPERTIES OF SKELETAL LATISSIMUS DORSI MUSCLE (LDM). Jacques Gagnonl, Jean-Aim6 Simoneau 3, Annie Boisvertl, Claude H. C6ti2, Sonia Roy’, Jean P’erronl Christine Desbiens’, Michel Martini. Jean Deslauriersl, Department of Medicinel, Physiotherapy2 and LABSAP 3, Laval University, QuCbec, Canada. To describe the extent of the variation in the metabolic profile (MP) and contractile properties (CP) of the human LDM, 30 biopsies were obtained Tom LDM during surgical thoracotomy. Mean age was 63.7k7.6 yr (&SD) (range 48-75, sex; 79 23M). MP included glycolytic (phosphofructokinase;PFK, glyceraldehyde PO4 dehydrogenase;GAPDH), aerobic-oxidative (citrate synthase;CS, hydroxyacylCoA dehydrogenase; HADH, cytochrome oxidase;COX) marker enzymes and creatine kinase (CK) ( all U/g). CP were measured in vitro at 37YY with a fresh dissected bundle. Time to peak (TPT) and half-relaxation time (I~R~msec) were obtained from a twitch followed by a frequency-force curve to calculate the maximum tetanic tension (Po;N/cm*). Two separate standardized fatigue protocols were used to study muscle resistance and viability. PFK GAPDH CS HADH @OX CK TPT 1ltRT Mean&SD 2y7i5 4m143 6.7ti.O 8.3k1.8 3.5k1.4 293*79 78+11 9w3 126 Range 177-590 3.8-10.8 4.6-12.9 1.4-6.8 155442 55-96 60-152 6-22 cv 37.6% 35.6% 29.4% 21.6% 41.4% 26.8% 13.7% 26% 40% These results reveal the existence of large interindividual variability in MP and CP. MP, CP, fatigue resistance and viability of LDM can be used to select patients who could benefit of the cardiomyoplasty. s.43
Cell
Cardiol
PI14
EFFECT OF THE NTCB, N-TERMINAL FRAGMENT OF CALDESMON ON MYOSIN ASSOCIATION WITH THE TRITON-INSOLUBLe CYTOSRELETON OF PLATELETS. Department of Physiology & Biophysics, University of M.E. Hemric and J.R. Haeberle. Vermont, Burlington, VT 05405 USA we have previously shown that a smooth and Using an in vitro motility assay, promotes actomyosin interaction and crossbridge nonmuscle protein, caldesmon, cycling at near physiological ionic strengths (Hemric, M.E. and Haeberle, J.R. We showed that this promotion was due to the formation (1992) Biophys. J. 61, A6). of actin-caldesmon-myosin complexes by using the NTCB, myosin-binding fragment of Now we have investigated caldesmon as a competitive inhibitor of complex formation. whether actin-caldesmon-myosin complexes promote actomyosin interaction in viva, The association of myosin with using platelet activation as an experimental model. a Triton-insoluble cytoskeleton increases during platelet activation and was attributed to light chain phosphorylation (Fox, J.E.B. and Phillips, D.R. (1982) J. Biol. Chem. 257, 4120-4126). We have reproduced these cytoskeletal changes and have used the NTCB, myosin-binding fragment of caldesmon to investigate whether actincaldesmon-myosin complexes are involved in this promotion of actomyosin interaction. Myosin association with the Triton-insoluble cytoskeleton was competitively These results suggest that myosininhibited by the myosin-binding fragment. caldesmon-actin complexes occur in viva and are involved in the association of myosin with the Triton-insoluble cytoskeleton during platelet activation.
PI15
STIMULATION BATE DEPENDENT ATTENUATION OF PHARMACOLOGICALLY INCREASED EFFECTIVE REFRACTORY PERIOD. Paul &miff, Maurice Briggs, Alan Ezrin, Cardiovss. Pharm., Sterling Winthrop PRD, Rensselaer NY, 12144. The effectiveness (increased effective refractory period, ERP) of most antiarrhythmics is attenuated as heart rate is increased. This study determines the relationship of drug increased ERP and rate dependent attenuation of ERP. The rate dependent effects of Disopyramide (DIS), Flecainide (FLC), Sematilide (SEM), Dofetilide @OF) and Sotalol (SOT) on El@ were evaluated in a rabbit heart Langendorff model. FXP was determined pre- and post- drug (15 min. exposure) at four rates 1210, 150, 180, and 220 stim / min. The ERP determined pre-drug at each stimulation rate was subtracted from ERP determined after each drug concentration (A ERP). A ERP increases of 20 msec or more were considered
24 (Supplement
physiologically
III)
significant.
(1992)
DIS
10 & 30 FM,
FLC
1 & 3 FM,
SEM
10 & 30 PM,
DOF
0.003, 0.01 & 0.03 PM and SOT 10, 30 & 100 PM had similar responses. The rate dependent attenuation of A m was greater with increased initial A ERP. The slopes of the A ERP vs rate relationship were significantly different from zero indicating that A ERP decreased as heart rate increased. The A ERP vs rate slopes were regressed against the A ERP at 120 stimlmin (r= .872, n=50, m=-0.005, b=O.O23) which defmes the “normal” attenuation relationship. Drugs which have responses positive to the 95 % confidence interval for this relationship would be less attenuated by rate. The relationship for SOT was positive while the other tested agents were not different from the “normal” relationship. This analysis allows drugs to be identified which are less attenuated by increased heart rate.
/‘I16
HUMAN VARIATION IN THE METABOLIC PROFILE AND CONTRACTILE PROPERTIES OF SKELETAL LATISSIMUS DORSI MUSCLE (LDM). Jacques Gagnonl, Jean-Aim6 Simoneau 3, Annie Boisvertl, Claude H. C6ti2, Sonia Roy’, Jean P’erronl Christine Desbiens’, Michel Martini. Jean Deslauriersl, Department of Medicinel, Physiotherapy2 and LABSAP 3, Laval University, QuCbec, Canada. To describe the extent of the variation in the metabolic profile (MP) and contractile properties (CP) of the human LDM, 30 biopsies were obtained Tom LDM during surgical thoracotomy. Mean age was 63.7k7.6 yr (&SD) (range 48-75, sex; 79 23M). MP included glycolytic (phosphofructokinase;PFK, glyceraldehyde PO4 dehydrogenase;GAPDH), aerobic-oxidative (citrate synthase;CS, hydroxyacylCoA dehydrogenase; HADH, cytochrome oxidase;COX) marker enzymes and creatine kinase (CK) ( all U/g). CP were measured in vitro at 37YY with a fresh dissected bundle. Time to peak (TPT) and half-relaxation time (I~R~msec) were obtained from a twitch followed by a frequency-force curve to calculate the maximum tetanic tension (Po;N/cm*). Two separate standardized fatigue protocols were used to study muscle resistance and viability. PFK GAPDH CS HADH @OX CK TPT 1ltRT Mean&SD 2y7i5 4m143 6.7ti.O 8.3k1.8 3.5k1.4 293*79 78+11 9w3 126 Range 177-590 3.8-10.8 4.6-12.9 1.4-6.8 155442 55-96 60-152 6-22 cv 37.6% 35.6% 29.4% 21.6% 41.4% 26.8% 13.7% 26% 40% These results reveal the existence of large interindividual variability in MP and CP. MP, CP, fatigue resistance and viability of LDM can be used to select patients who could benefit of the cardiomyoplasty. s.43