The present study examined whether 20-hydroxyeicosatetraenoic acid (HETE) contributes to the vasoconstrictor effect of angiotensin II (ANG II) in renal microvessels by preventing activation of the large conductance Ca2+-activated K+ channel (KCa) in vascular smooth muscle (VSM) cells. ANG II increased the production of 20-HETE in rat renal microvessels. This response was attenuated by the 20-HETE synthesis inhibitors, 17-ODYA and HET0016, a phospholipase A2 inhibitor AACOF3, and the AT1 receptor blocker, Losartan, but not by the AT2 receptor blocker, PD123319. ANG II (10-11 to 10-6 M) dose-dependently decreased the diameter of renal microvessels by 41 ± 5%. This effect was blocked by 17-ODYA. ANG II (10-7 M) did not alter KCa channel activity recorded from cell-attached patches on renal VSM cells under control conditions. However, it did reduce the NPo of the KCa channel by 93.4 ± 3.1% after the channels were activated by increasing intracellular calcium levels with ionomycin. The inhibitory effect of ANG II on KCa channel activity in the presence of ionomycin was attenuated by 17-ODYA, AACOF3, and the phospholipase C (PLC) inhibitor U-73122. ANG II induced a peak followed by a steady-state increase in intracellular calcium concentration in renal VSM cells. 17-ODYA (10-5 M) had no effect on the peak response, but it blocked the steady-state increase. These results indicate that ANG II stimulates the formation of 20-HETE in rat renal microvessels via the AT1 receptor activation and that 20-HETE contributes to the vasoconstrictor response to ANG II by blocking activation of KCa channel and facilitating calcium entry.

This study examined the effect of substitution of a 2.4-megabase pair (Mbp) region of Brown Norway (BN) rat chromosome 1 (RNO1) between 258.8 and 261.2 Mbp onto the genetic background of fawn-hooded hypertensive (FHH) rats on autoregulation of renal blood flow (RBF), myogenic response of renal afferent arterioles (AF-art), K ϩ channel activity in renal vascular smooth muscle cells (VSMCs), and development of proteinuria and renal injury. FHH rats exhibited poor autoregulation of RBF, while FHH.1BN congenic strains with the 2.4-Mbp BN region exhibited nearly perfect autoregulation of RBF. The diameter of AF-art from FHH rats increased in response to pressure but decreased in congenic strains containing the 2.4-Mbp BN region. Protein excretion and glomerular and interstitial damage were significantly higher in FHH rats than in congenic strains containing the 2.4-Mbp BN region. K ϩ channel current was fivefold greater in VSMCs from renal arterioles of FHH rats than cells obtained from congenic strains containing the 2.4-Mbp region. Sequence analysis of the known and predicted genes in the 2.4-Mbp region of FHH rats revealed amino acid-altering variants in the exons of three genes: Add3, Rbm20, and Soc-2. Quantitative PCR studies indicated that Mxi1 and Rbm20 were differentially expressed in the renal vasculature of FHH and FHH.1BN congenic strain F. These data indicate that transfer of this 2.4-Mbp region from BN to FHH rats restores the myogenic response of AF-art and autoregulation of RBF, decreases K ϩ current, and slows the progression of proteinuria and renal injury. kidney; glomerulosclerosis; chronic renal failure; renal hemodynamics THE FAWN-HOODED HYPERTENSIVE (FHH) rat is a genetic model of hypertension (33) that develops proteinuria, glomerulosclerosis (21,30,37,47), and chronic kidney disease (22,(25)(26)(41)(42). We have previously reported that the development of proteinuria and glomerular injury in FHH rats is associated with an impaired autoregulation of renal blood flow (RBF), glomerular filtration rate (GFR), and glomerular capillary pressure (Pgc) (24,40,43,48). Genetic cosegregation studies identified five quantitative trait loci (QTLs) linked to the development of proteinuria in F2 crosses of FHH and AugustCopenhagen inbred (ACI) rats (4 -5, 36). The rat chromosome (RN) regions are Rf-1 and Rf-2 on RNO1, Rf-3 on RNO3, Rf-4 on RNO14, and Rf-5 on RNO17. The Rf-1 QTL is of particular interest in that it lies within a region that is homologous to an area on human chromosome 10 linked to the development of diabetic nephropathy (19) and end-stage renal disease (18). More recent studies identified a G-to-A mutation in the start codon of Rab38, a gene in the Rf-2 QTL that influences protein trafficking and contributes to the development of proteinuria in FHH rats (32). However, the genes in the Rf-1 region that contribute to the development of proteinuria and renal disease in FHH rats and the mechanisms involved are unknown.We have previously reported that substitution of a 99.4-megabase pair (Mbp) reg...

(30,38). RyRs are regulated by a number of cytosolic constituents that either enhance (e.g., ATP) or inhibit (e.g., Mg 2ϩ and protons) its activity (for reviews, see Refs. 17 and 26). Ischemic conditions lead to the inhibition of oxidative phosphorylation, mitochondrial uncoupling, and collapse of the mitochondrial membrane potential (⌬⌿ m ). Depolarized mitochondria lose the capacity for Ca 2ϩ uptake and Ca 2ϩ buffering, and ischemia-induced cytosolic acidification (through mitochondrial H ϩ extrusion and lactic acid production by the shifting of metabolism to anaerobic glycolysis), depletion of the cellular ATP pool, and the concomitant increase of free [Mg 2ϩ ] i levels lead to severe impairment of SR Ca 2ϩ release and excitation-contraction (E-C) coupling.The aim of this study was to investigate how intact mitochondrial Ca 2ϩ signaling and energy (ATP) production affect SR Ca 2ϩ release and E-C coupling in atrial myocytes. To eliminate mitochondrial ATP production and Ca 2ϩ buffering, we used the protonophore FCCP to depolarize ⌬⌿ m . We investigated the effect of mitochondrial uncoupling on action potential (AP)-triggered and spontaneous (Ca 2ϩ waves) SR Ca 2ϩ release and their interactions with cellular ATP, Mg 2ϩ , Na ϩ , and intracellular pH (pH i ) homeostasis. We found that in intact atrial myocytes, depolarization of ⌬⌿ m resulted in a biphasic effect on SR Ca 2ϩ release, consisting of an initial inhibition followed by stimulation. The initial inhibition was the result of suppression of RyR channel activity by a decrease in [ATP], an increase of [Mg 2ϩ ] i , and cytoplasmic acidification. The latter stimulation resulted from cytosolic Na ϩ and Ca 2ϩ accumulation, presumably due to Na ϩ /H ϩ exhanger (NHX) and Na ϩ /Ca 2ϩ exchanger (NCX) activity and reduced mitochondrial Ca 2ϩ buffering. Cytosolic Ca 2ϩ accumulation led to SR Ca 2ϩ uptake by SERCA fueled by compensatory

We previously reported that attachment of atrial myocytes to the extracellular matrix protein laminin (LMN), decreases adenylate cyclase (AC)/cAMP and increases β 2 -adrenergic receptor (AR) stimulation of L-type Ca 2+ current (I Ca,L ). This study therefore sought to determine whether LMN enhances β 2 -AR signalling via a cAMP-independent mechanism, i.e.