Effect of β3-adrenergic receptor on atrial L-type Ca(2+) current in rats with chronic heart failure

Area of Science:

• Cardiology
• Pharmacology
• Molecular Biology

Background:

• Chronic heart failure (CHF) is a complex condition affecting cardiac structure and function.
• Left atrial (LA) remodeling is a significant consequence of CHF, impacting overall cardiovascular health.
• Understanding the molecular mechanisms underlying LA dysfunction in CHF is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the effects of the selective β3-adrenoreceptor agonist BRL-37344 on left atrial (LA) structure and function in a rat model of chronic heart failure (CHF).
• To examine the impact of BRL-37344 on L-type Ca(2+) current (Ica,L) and the mRNA expression of the L-type Ca(2+) channel α2δ-2 subunit (Cacna2d2) in the context of CHF-induced LA remodeling.

Main Methods:

• Twenty-four male Wistar rats were assigned to normal control or CHF groups.
• CHF rats received either no treatment or BRL-37344 (0.4 nmol/kg, IV, twice weekly for four weeks).
• Echocardiography was used to assess LA dimensions and ejection fraction; electrophysiology and RT-PCR were used to measure Ica,L and Cacna2d2 mRNA expression.

Main Results:

• BRL-37344 treatment resulted in a significant increase in LA diameter and a decrease in LA ejection fraction compared to both normal control and CHF control groups.
• No significant differences were observed in Ica,L density between the BRL-treated group and the CHF control group.
• mRNA expression levels of Cacna2d2 in the LA myocytes did not differ between the BRL-treated group and the CHF control group.

Conclusions:

• β3-Adrenoreceptor stimulation with BRL-37344 exacerbates LA enlargement and impairs LA function in rats with chronic heart failure.
• The observed detrimental effects of BRL-37344 on LA structure and function in CHF are not mediated by alterations in Ica,L or Cacna2d2 mRNA expression in LA myocytes.