Abstract MP05: Knockdown of Gamma-adducin Expression Impairs the Myogenic Response of the Cerebral and Renal Arterioles
We recently identified a region on chromosome 1 containing 15 genes that rescues the impaired myogenic response in the afferent arteriole (Af-art) and the development of renal injury in Fawn Hood Hypertensive (FHH) rats. We also found an inactivating K572Q mutation in the gamma-Adducin (Add3) gene in FHH rats in this region that may play a causal role. To test this hypothesis, the present study examed the effect of knockdown of the expression of Add3 with DsiRNA on the myogenic response of renal and cerebral arterioles. A newly designed 27-mer Add3 DsiRNA blocked the expression of the Add3 protein in 293 cells and reduced Add3 mRNA expression in a dose-dependent manner up to 75% in cultured middle cerebral arteries (MCA). The inner diameter of MCA and renal Af-art 36 hours after co-transfection of Add3 DsiRNA dilated by 9 ± 2% and 4 ± 3%, respectively, in response to an elevation in transmural pressure from 60 to 140 mmHg. In contrast, these vessels still constricted normally by 11± 2% and 10 ± 1% in vessels transfected with scrambled siRNA. Add3 DsiRNA had no effect on the vasoconstrictor response of the Af-art to NE (10-7 M). The large conductance calcium sensitive potassium (BK) current was 5-fold higher in vascular smooth muscle cells (VSMC) freshly isolated from the MCA that were transfected with Add3 DsiRNA as indicated by the appearance of SiGLO red fluorescence compared with that seen in non-transfected cells. Administration of IBTX normalized the elevated BK channel current recorded from VSMC transfected with Add3 DsiRNA, but it had little effect in non-transfected cells. These results indicate that knockdown of the expression of Add3 impairs the myogenic response of both MCA and Af-art and it is associated with an elevation in BK channel activity. It also supports the hypothesis that the K572Q mutation of Add3 found in FHH rats may play a causal role in the impaired myogenic response and autoregulation of renal and cerebral blood flow by elevating BK channel activity in VSMC.
Author Disclosures: F. Fan: None. M.R. Pabbidi: None. Y. Ge: None. R.J. Roman: None.
- © 2015 by American Heart Association, Inc.