Do TRPV channels contribute to myogenic tone in skeletal muscle arterioles?

TRPV channels may play important physiological roles in smooth muscle cells (SMC) and endothelial cells (EC), but their expression and function in skeletal muscle arterioles is unclear. Therefore, we examined TRPV expression in hamster and rat cremasteric arterioles using qRT‐PCR and immunocytochemistry (ICC) on isolated SMC and EC and Western blots of vessel homogenates. In addition, isolated arterioles were cannulated, pressurized and diameter changes recorded in response to a TRPV antagonist and agonist. qRT‐PCR showed expression of TRPV1, 2 and 4 in SMC and TRPV1 and 4 in EC, with EC TRPV4 most abundant. Western blots confirmed expression of TRPV1, 2 and 4. ICC revealed uniform expression of TRPV1, 2 and 4 in SMC. In contrast, TRPV1 was expressed in a subset of EC, and TRPV2 was detected at one pole of the EC nuclei. The TRPV blocker, ruthenium red (RR: 1 – 10 μM) led to concentration‐dependent dilation of cannulated arterioles (1μM: 8.56μm ± 0.71; 10μM:15.65μm ± 0.77) suggesting that at least one TRPV member contributes to myogenic tone. The TRPV4 agonist, 4α‐Phorbol 12,13‐didecanoate (300 nM) caused a small constriction (3.86μm ± 1.11), that was not eliminated by pretreatment with RR (10 μM) (3.63μm ± 1.67), suggesting that TRPV4 does not contribute to myogenic tone in skeletal muscle arterioles. We hypothesize that TRPV1, 2 or other TRPV members may be involved in the RR‐induced dilation. Supported by HL32469.