Skip to main content
padlock icon - secure page this page is secure

Cyclic GMP protein kinase activity is reduced in thyroxine-induced hypertrophic cardiac myocytes

Buy Article:

$52.00 + tax (Refund Policy)

Summary

1. We tested the hypothesis that the cGMP-dependent protein kinase has major negative functional effects in cardiac myocytes and that the importance of this pathway is reduced in thyroxine (T4; 0.5 mg/kg per day for 16 days) hypertrophic myocytes.

2. Using isolated ventricular myocytes from control (n = 7) and T4-treated (n = 9) rabbit hypertrophic hearts, myocyte shortening was studied with a video edge detector. Oxygen consumption was measured using O2 electrodes. Protein phosphorylation was measured autoradiographically.

3. Data were collected following treatment with: (i) 8-(4-chlorophenylthio)guanosine-3′,5′-monophosphate (PCPT; 10−7 or 10−5 mol/L); (ii) 8-bromo-cAMP (10−5 mol/L) followed by PCPT; (iii) β-phenyl-1,N2-etheno-8-bromoguanosine-3′,5′-monophosphorothioate, SP-isomer (SP; 10−7 or 10−5 mol/L); or (iv) 8-bromo-cAMP (10−5 mol/L) followed by SP.

4. There were no significant differences between groups in baseline percentage shortening (Pcs; 4.9 ± 0.2 vs 5.6 ± 0.4% for control and T4 groups, respectively) and maximal rate of shortening (Rs; 64.8 ± 5.9 vs 79.9 ± 7.1 µm/ s for control and T4 groups, respectively). Both SP and PCPT decreased Pcs (−43 vs−21% for control and T4 groups, respectively) and Rs (−36 vs−22% for control and T4 groups, respectively), but the effect was significantly reduced in T4 myocytes. 8-Bromo-cAMP similarly increased Pcs (28 vs 23% for control and T4 groups, respectively) and Rs (20 vs 19% for control and T4 groups, respectively). After 8-bromo-cAMP, SP and PCPT decreased Pcs (−34%) and Rs (−29%) less in the control group. However, the effects of these drugs were not altered in T4 myocytes (Pcs −24%; Rs −22%). Both PCPT and cAMP phosphorylated the same five protein bands. In T4 myocytes, these five bands were enhanced less.

5. We conclude that, in control ventricular myocytes, the cGMP-dependent protein kinase exerted major negative functional effects but, in T4-induced hypertrophic myocytes, the importance of this pathway was reduced and the interaction between cAMP and the cGMP protein kinase was diminished.
No References
No Citations
No Supplementary Data
No Article Media
No Metrics

Keywords: cAMP; cGMP; cGMP protein kinase; cardiac myocyte; rabbit; thyroxine-induced hypertrophy

Document Type: Research Article

Affiliations: Heart and Brain Circulation Laboratory, Departments of Physiology & Biophysics and Surgery, University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School, Piscataway, New Jersey, USA

Publication date: December 1, 2003

  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more