TY - JOUR
T1 - Negative functional effects of cGMP mediated by cGMP protein kinase are reduced in T4 cardiac myocytes
AU - Engel, Samuel
AU - Yan, Lin
AU - Weiss, Harvey
AU - Scholz, Peter
N1 - Funding Information:
This work was supported in part by USPHS Grant # HL40320.
PY - 2001/6/1
Y1 - 2001/6/1
N2 - We tested the hypothesis that in isolated rabbit cardiac myocytes, the negative functional effects of cyclic GMP are partly mediated by cyclic GMP-dependent protein kinase activity, and that these effects are altered in thyroxine (T4, 0.5 mg/kg/day for 16 days)-induced hypertrophic myocytes. Using isolated ventricular myocytes from control (N = 8) and T4 (N = 8) hypertrophic hearts, data for percent cell shortening (%) and maximum rate of contraction (μm/s) were collected using a video edge detector at baseline, after the addition of 10-6 M 8-bromo-cyclic GMP (8-Br-cGMP), 10-5 M 8-Br-cGMP, and 10-6 M KT5823 (10-methoxy-10-methoxycarbonyl-9, 10, 11, 12-tetrahydro-9, 12-epoxy-(1H)-diinidolo [1, 2, 3, f-g: 3′, 2′, 1′-k-j]-pyrrolidino-[3,4-i] [1,6]-benzodiazocin-2-methyl-1-one, cyclic GMP protein kinase inhibitor). Protein phosphorylation was determined autoradiographically after gel electrophoresis. In both control and T4 myocytes, 8-Br-cGMP caused a significant decrease in percent shortening (5.56 ± 0.49% to 3.02 ± 0.47% in control and 4.34 ± 0.33% to 3.13 ± 0.17% in T4 myocytes) and maximal rate of contraction 57.35 ± 6.05 to 36.82 ± 3.17 μm/s in control and 58.49 ± 3.28 to 42.88 ± 2.29 μm/s in T4 myocytes). KT5823 significantly increased percent shortening to 3.77 ± 0.28% and rate to 48.68 ± 4.71 μm/s after 8-Br-cGMP only in control myocytes. In T4 myocytes, the changes in percent shortening and rate after KT5823 were not significant. Protein phosphorylation was increased by 8-Br-cGMP in control and to a lesser extent in T4 myocytes, but the increment was reduced by KT-5823 in control only. These data demonstrated that cyclic GMP had negative functional effects partially mediated by cyclic GMP protein kinase in control myocytes. Cyclic GMP also exerted negative functional effects in thyroxine-induced hypertrophic myocytes, but cyclic GMP protein kinase activity was not an important regulator of these effects in T4 ventricular myocytes.
AB - We tested the hypothesis that in isolated rabbit cardiac myocytes, the negative functional effects of cyclic GMP are partly mediated by cyclic GMP-dependent protein kinase activity, and that these effects are altered in thyroxine (T4, 0.5 mg/kg/day for 16 days)-induced hypertrophic myocytes. Using isolated ventricular myocytes from control (N = 8) and T4 (N = 8) hypertrophic hearts, data for percent cell shortening (%) and maximum rate of contraction (μm/s) were collected using a video edge detector at baseline, after the addition of 10-6 M 8-bromo-cyclic GMP (8-Br-cGMP), 10-5 M 8-Br-cGMP, and 10-6 M KT5823 (10-methoxy-10-methoxycarbonyl-9, 10, 11, 12-tetrahydro-9, 12-epoxy-(1H)-diinidolo [1, 2, 3, f-g: 3′, 2′, 1′-k-j]-pyrrolidino-[3,4-i] [1,6]-benzodiazocin-2-methyl-1-one, cyclic GMP protein kinase inhibitor). Protein phosphorylation was determined autoradiographically after gel electrophoresis. In both control and T4 myocytes, 8-Br-cGMP caused a significant decrease in percent shortening (5.56 ± 0.49% to 3.02 ± 0.47% in control and 4.34 ± 0.33% to 3.13 ± 0.17% in T4 myocytes) and maximal rate of contraction 57.35 ± 6.05 to 36.82 ± 3.17 μm/s in control and 58.49 ± 3.28 to 42.88 ± 2.29 μm/s in T4 myocytes). KT5823 significantly increased percent shortening to 3.77 ± 0.28% and rate to 48.68 ± 4.71 μm/s after 8-Br-cGMP only in control myocytes. In T4 myocytes, the changes in percent shortening and rate after KT5823 were not significant. Protein phosphorylation was increased by 8-Br-cGMP in control and to a lesser extent in T4 myocytes, but the increment was reduced by KT-5823 in control only. These data demonstrated that cyclic GMP had negative functional effects partially mediated by cyclic GMP protein kinase in control myocytes. Cyclic GMP also exerted negative functional effects in thyroxine-induced hypertrophic myocytes, but cyclic GMP protein kinase activity was not an important regulator of these effects in T4 ventricular myocytes.
KW - (Rabbit)
KW - Hypertrophy
KW - Myocyte
KW - Nitric oxide (NO)
KW - Second messenger
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U2 - 10.1016/S0014-2999(01)00993-1
DO - 10.1016/S0014-2999(01)00993-1
M3 - Article
C2 - 11408045
AN - SCOPUS:0035368721
SN - 0014-2999
VL - 421
SP - 23
EP - 30
JO - European Journal of Pharmacology
JF - European Journal of Pharmacology
IS - 1
ER -