In this study, we determined a pharmacological profile of store-operated channels (SOCs) in smooth muscle cells of rabbit pial arterioles. Ca2+-indicator dyes, fura-PE3 or fluo-4, were used to track [Ca2+]i and 10 μM methoxyverapamil (D600) was present in all experiments on SOCs to prevent voltage-dependent Ca2+ entry. Store depletion was induced using thapsigargin or cyclopiazonic acid.
SOC-mediated Ca2+ entry was inhibited concentration dependently by Gd3+ (IC50 101 nM). It was also inhibited by 10 μM La3+ (70% inhibition, N=5), 100 μM Ni2+ (57% inhibition, N=5), 75 μM 2-aminoethoxydiphenylborate (66% inhibition, N=4), 100 μM capsaicin (12% inhibition, N=3) or preincubation with 10 μM wortmannin (76% inhibition, N=4). It was completely resistant to 1 μM nifedipine (N=5), 10 μM SKF96365 (N=6), 10 μM LOE908 (N=14), 10–100 μM ruthenium red (N=1+2), 100 μM sulindac (N=4), 0.5 mM streptomycin (N=3) or 1 : 10,000 dilution Grammostolla spatulata venom (N=4).
RT–PCR experiments on isolated arteriolar fragments showed expression of mRNA species for TRPC1, 3, 4, 5 and 6.
The pharmacological profile of SOC-mediated Ca2+ entry in arterioles supports the hypothesis that these SOCs are distinct from tonically active background channels and several store-operated and other nonselective cation channels described in other cells. Similarities with the pharmacology of TRPC1 support the hypothesis that TRPC1 is a subunit of the arteriolar smooth muscle SOC.>
British Journal of Pharmacology (2003) 139, 955–965. doi:10.1038/sj.bjp.0705327