Abstract
Background:
In veterinary medicine, voltage-gated calcium channels (VGCCs) are key drug targets. Calcium channel blockers (CCBs) are the standard treatment for common feline diseases, such as systemic hypertension and hypertrophic cardiomyopathy. However, therapeutic strategies are limited due to the adverse effects of existing drugs like amlodipine, such as activation of the renin-angiotensin-aldosterone system. A critical lack of feline-specific data on the tissue distribution of VGCC subtypes fundamentally hinders the safe and effective application of CCBs in cats. This is because knowledge from other species is often not translatable due to the unique metabolic pathways in cats.

Aim:
To fill this critical data gap, the present study created the first baseline quantitative map of the mRNA expression of seven major VGCC α1-subunits across a comprehensive range of feline tissues.

Methods:
Twelve tissue types were collected from a single 16-month-old male cat. Using a validated TaqMan probe-based quantitative real-time PCR assay, we measured the relative mRNA expression of seven CaV α1-subunit genes: CACNA1S (CaV1.1), CACNA1C (CaV1.2), CACNA1D (CaV1.3), CACNA1F (CaV1.4), CACNA1B (CaV2.2), CACNA1G (CaV3.1), and CACNA1H (CaV3.2). Relative transcript abundance was calculated using the 2-ΔCt method with 18S rRNA as the endogenous control for normalization.

Results:
The seven VGCC genes exhibited distinct, tissue-specific expression patterns. CACNA1S expression was predominantly localized to skeletal muscle. The heart showed the highest expression of CACNA1C and CACNA1H. The brain displayed prominent CACNA1B, CACNA1C, and CACNA1G expression. The mesenteric lymph node also showed significant CACNA1C, CACNA1F, and CACNA1G expression. Conversely, the liver and pancreas consistently displayed very low expression for most of the channel genes investigated.

Conclusion:
This study provides the first foundational mRNA expression map of major VGCC α1-subunits in feline tissues. The results reveal unique expression profiles that highlight both conserved physiological functions and significant differences compared to other species, particularly in cardiac and lymphoid tissues. These molecular data are vital for advancing feline pharmacology by enabling more accurate predictions of the therapeutic and adverse effects of CCBs and provide a critical resource for future investigations into feline channelopathies.

Key words: Felis catus; Voltage-gated calcium channels; Gene expression; Quantitative PCR; Calcium channel blockers.