Rod-type cyclic nucleotide-gated cation channel is expressed in vascular endothelium and vascular smooth muscle cells

Ca(++)-permeable nonselective cation channels mediate the entry of extracellular Ca++ in vascular endothelium. They are also partly responsible for Ca++ entry in vascular smooth muscle cells (SMCs). The molecular identities of these channels have not been identified. The aim of this study is to examine whether rod-type nucleotide-gated nonselective cation (CNG1) channel, a channel which has been molecularly cloned, is related to the nonselective channels in vascular cells.

We used RT-PCR, molecular cloning, northern Blot and in situ hybridization to examine the expression of CNG1 mRNA in a variety of guinea pig and rat blood vessels with different diameters and in cultured vascular endothelial cells and vascular smooth muscle cells.

We have cloned a 402-bp partial cDNA of CNG1 channel from guinea pig mesenteric arteries. RT-PCR and southern blot results indicate that the CNG1 mRNA is expressed in both cultured vascular endothelial and cultured vascular SMCs. Northern blot revealed the transcripts of approximately 3.2 kb, approximately 5.0 kb, and approximately 1.8 kb in cultured endothelial cells. In situ hybridization yielded strong labeling in endothelium layer of aorta, medium-sized mesenteric arteries, and small mesenteric arteries.

Our findings suggest a potential role of CNG protein for Ca++ entry in vascular endothelium and vascular smooth muscles. The high expression of CNG1 mRNA in the endothelium of medium-sized arteries and small-sized arteries implicates a possible involvement of CNG1 protein in the regulation of blood supply to different regions and in the regulation of arterial blood pressure.