Related Experiment Videos
Biochemical alterations in cardiac hypertrophy
Insights
Cardiac hypertrophy in hypertensive rats shows similar functional changes but different biochemical defects. The balance between alpha- and beta-adrenergic pathways may influence cardiac hypertrophy in hypertension.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Hypertension Research
Background:
- Cardiac hypertrophy is a common complication of hypertension.
- Altered adrenergic receptor signaling is implicated in cardiac hypertrophy.
- Understanding the specific biochemical defects is crucial for therapeutic development.
Purpose of the Study:
- To investigate the distinct biochemical alterations in cardiac adrenergic signaling pathways in two models of hypertension-induced cardiac hypertrophy: two-kidney, one clip renal hypertensive rats (RHR) and spontaneously hypertensive rats (SHR).
- To compare the defects in excitation-response pathways between RHR and SHR models.
Main Methods:
- Assessment of inotropic responsiveness to adenylate cyclase-mediated agonists (isoproterenol, glucagon) and alpha 1 adrenergic receptor agonist (phenylephrine) in RHR and SHR.
- Analysis of beta-adrenergic receptors, alpha 1 receptors, adenylate cyclase activity, and cAMP-stimulated protein kinase activity in cardiac tissue from both models.
Main Results:
- Both RHR and SHR exhibited decreased inotropic responsiveness to beta-adrenergic and alpha 1 adrenergic agonists.
- SHR showed decreased beta-adrenergic receptors, increased alpha 1 receptors, unchanged cyclase activity, and decreased cAMP-stimulated protein kinase.
- RHR displayed increased beta-receptors, decreased alpha 1 receptors, decreased adenylate cyclase activity (due to reduced nucleotide regulatory protein activity), and increased microsomal cAMP-stimulated protein kinase.
Conclusions:
- Despite similar functional impairments in cardiac hypertrophy, the underlying biochemical defects in adrenergic signaling pathways differ significantly between RHR and SHR.
- The observed shifts in the balance between alpha- and beta-adrenergic pathways may represent a compensatory mechanism.
- These distinct biochemical alterations likely play a role in the pathophysiology of cardiac hypertrophy associated with different forms of hypertension.
Abstract:
In both two-kidney, one clip renal hypertensive rats (RHR) and spontaneously hypertensive rats (SHR) with myocardial hypertrophy, inotropic responsiveness to adenylate cyclase mediated agonists, such as isoproterenol and glucagon is decreased, as is the responsiveness to phenylephrine acting via alpha 1 adrenergic receptors. However, defects in the excitation response pathway differ in the two hypertensive models. In SHR beta-adrenergic receptors are decreased, alpha 1 receptors increased, cyclase activity is unchanged but c-AMP stimulated protein kinase is decreased. In RHR beta-receptors are increased, alpha 1 receptors decreased, adenylate cyclase activity decreased due to decreased nucleotide regulatory protein activity, and microsomal cAMP stimulated protein kinase is increased. We conclude that, although functional changes in hypertensive cardiac hypertrophy are similar, the underlying biochemical alterations are different. The shift in balance between alpha- and beta-adrenergic pathways may be a compensatory mechanism and play a role in the pathophysiology of cardiac hypertrophy.