Background
Methods
Rat model
Echocardiography
Solutions for skinned myocardial strips
Skinned myocardial strips
Tension-velocity relationship
Native thin filament isolation
In vitro motility assay
Isolated cardiomyocyte function
Myosin isoform determination and western blots
Cardiac element content measurements
mRNA analysis and quantitative PCR
Statistical analysis
Results
Animal characteristics
HG (n=8) | nonHG (8) | |
---|---|---|
Age (wks) | 19.8 ± 0.3 | 20.1 ± 0.4 |
PTU diet (wks) | 12.8 ± 0.3 | 13.1 ± 0.4 |
Body mass (g) | 217 ± 5 † | 278 ± 15 |
Glucose 1 wks (mg/dL) | 287 ± 20 | no measure |
Glucose 6 wks (mg/dL) | 422 ± 21 †† | 75 ± 6 |
Heart rate (bpm) | 213.3 ± 9.1 | 229.1 ± 5.0 |
LVD dias (mm) | 6.99 ± 0.18 | 6.88 ± 0.26 |
LVD sys (mm) | 4.40 ± 0.16 | 4.41 ± 0.25 |
Fractional Shortening (%) | 37.0 ± 1.7 | 35.9 ± 2.3 |
Ejection Fraction (%) | 74.7 ± 1.9 | 73.0 ± 2.7 |
Ejection Time (ms) | 146.6 ± 5.6 # | 135.8 ± 2.7 |
Circum. Velocity (circ/s) | 2.56 ± 0.17 | 2.67 ± 0.21 |
LVPWT dias (mm) | 1.35 ± 0.09 | 1.23 ± 0.09 |
Myofilament performance
Myofilament calcium sensitivity
HG (n=6) | nonHG (6) | |
---|---|---|
Tmin (mN/mm2) | 4.24 ± 0.33 | 4.87 ± 0.18 |
Tmax (mN/mm2) | 15.8 ± 1.4 | 16.9 ± 1.7 |
Tdev (mN/mm2) | 11.6 ± 1.6 | 12.1 ± 1.8 |
pCa50 | 5.88 ± 0.02 | 5.89 ± 0.02 |
nHill | 3.41 ± 0.38 | 3.06 ± 0.16 |
(n=3) | (3) | |
VCa, NTF (µm/s) | 4.52 ± 0.30 | 4.62 ± 0.29 |
pCa50, NTF | 6.35 ± 0.07 | 6.32 ± 0.06 |
nHill, NTF | 1.36 ± 0.22 | 1.39 ± 0.23 |
Tension-velocity relationship
HG (n=6) | nonHG (6) | |
---|---|---|
a/Tmax (no units) | 0.501 ± 0.086 | 0.392 ± 0.102 |
b (10-3 ML/s) | 414 ± 104 | 347 ± 95 |
Vmax (10-3 ML/s) | 817 ± 125 | 899 ± 85 |
Vopt (10-3 ML/s) | 292 ± 45 | 291 ± 35 |
Topt/Tmax (%) | 35.8 ± 1.5 | 32.5 ± 2.8 |
Pmax (10-3 ML/s × T/Tmax) | 106 ± 18 | 98 ± 17 |
Cardiomyocyte sarcomere dynamics
Contraction function
Variable | HG | freq | HG×freq | zinc | HG×zinc | freq×zinc | HG×freq×zinc |
---|---|---|---|---|---|---|---|
Peak Shortening (%) | 0.013* | <0.001† | 0.008† | <0.001† | 0.941 | 0.619 | 0.424 |
Peak Shortening (μm) | 0.043* | <0.001† | 0.008† | <0.001† | 0.992 | 0.698 | 0.374 |
Max Shortening dSL/dt (μm/s) | 0.028* | <0.001† |
0.016*
| <0.001† | 0.922 | 0.624 | 0.582 |
Max Lengthening dSL/dt (μm/s) | 0.002* | <0.001† |
0.011*
| <0.001† | 0.833 | 0.121 | 0.827 |
Time to Peak (ms) | 0.712 | <0.001† | 0.295 | 0.354 | 0.158 | 0.153 | 0.674 |
Time to 10% return (ms) | 0.505 | <0.001† | 0.082# | 0.294 | 0.215 | 0.094# | 0.706 |
Time to 50% return (ms) | 0.230 | <0.001† | <0.001† | 0.554 | 0.249 | 0.368 | 0.534 |
Diastolic SL (μm) | <0.001† | <0.001† | 0.005† | 0.722 | 0.913 | 0.176 |
0.037*
|
Relaxation function
Variable | HG | freq | HG×freq |
---|---|---|---|
Peak – Diastolic Ratio (R) | 0.107 | 0.250 | 0.828 |
Area of Ratio Transient (R.ms) | 0.079# | <0.001† | 0.179 |
Time to Peak (ms) | 0.673 | <0.001† | 0.941 |
Time to 50% return (ms) | 0.111 | <0.001† | 0.546 |
Exponential Time Constant (ms) | 0.514 | <0.001† | 0.815 |
Diastolic Ratio (R) | 0.340 | 0.100 | 0.532 |
Cardiomyocyte calcium dynamics
Other post-translational modifications
Cardiac element content
Hypothyroid | Euthyroid | |||
---|---|---|---|---|
HG (n=8) | nonHG (8) | HG (6) | nonHG (6) | |
Ca | 101.2 ± 6.0 | 100.8 ± 7.4 | 284.4 ± 44.3* | 155.4 ± 32.9 |
Cu | 4.4 ± 0.2 | 3.9 ± 0.2 | 5.2 ± 0.3 * | 6.4 ± 0.2 |
Fe | 66.7 ± 3.0* | 58.7 ± 1.9 | 95.5 ± 2.5 † | 122.3 ± 7.5 |
K | 2316 ± 148 | 2053 ± 85 | 7369 ± 793 * | 5052 ± 566 |
Mg | 186.8 ± 8.9 | 177.3 ± 7.6 | 275.1 ± 13.6 | 257.8 ± 6.0 |
Na | 1863 ± 102 | 1788 ± 75 | 2325 ± 224 * | 1641 ± 186 |
P | 2158 ± 105 | 2012 ± 81 | 2726 ± 86 | 2711 ± 24 |
S | 2545±155 * | 2022 ± 102 | 3707 ± 163* | 3149 ± 95 |
Zn | 17.6 ± 0.7 | 17.7 ± 0.8 | 23.1 ± 1.1 | 22.2 ± 0.3 |
MT1a | - | - | 0.66 ± 0.13 * | 1.00 ± 0.05 |
ZnT2 | - | - | 0.76 ± 0.07 # | 1.00 ± 0.10 |
γ-GCSh | - | - | 1.30 ± 0.08 † | 1.00 ± 0.03 |