Dynorphin gene expression and release in the myocardial cell

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Neuroendocrinology

Background:

• The prodynorphin gene encodes precursors for endogenous opioid peptides.
• Opioid peptides, like dynorphin B, are involved in various physiological processes.
• Their role in cardiac function, particularly in adult ventricular myocytes, remains incompletely understood.

Purpose of the Study:

• To investigate the expression of the prodynorphin gene in cultured rat ventricular cardiac myocytes.
• To quantify prodynorphin mRNA and dynorphin B levels under different conditions.
• To explore the functional effects of K opioid receptor activation on intracellular calcium in cardiac myocytes.

Main Methods:

• Quantitative analysis of prodynorphin mRNA using solution hybridization RNase protection assay.
• Measurement of immunoreactive dynorphin B in cell culture medium and myocytes.
• Assessment of intracellular calcium levels in response to K opioid receptor agonists and antagonists.
• Investigation of the role of calcium channels using verapamil.

Main Results:

• High KCl treatment initially increased prodynorphin mRNA, followed by a progressive downregulation.
• Dynorphin B levels were higher in the medium than in myocytes, increasing after 4h KCl and decreasing after 24h.
• KCl-induced effects were blocked by verapamil, and K opioid receptor stimulation increased cytosolic calcium, independently of extracellular calcium.

Conclusions:

• Prodynorphin gene expression in cardiac myocytes is dynamically regulated by KCl.
• Dynorphin B acts as a K opioid receptor agonist influencing intracellular calcium.
• Opioid genes may modulate myocardial function via autocrine or paracrine signaling pathways.