Decrease in endothelium-derived hyperpolarizing factor (EDHF)-mediated dilatory function in large elastic arteries during hypertension is reversed after blood pressure normalization. arteries were not reduced in SHRs although morphological differences were found in the endothelium and smooth muscle. In WKY rats SHRs and enalapril-treated SHRs relaxations were mediated by small- large- and intermediate-conductance calcium-activated potassium channels which were distributed in the endothelium smooth muscle and both layers respectively. However only WKY hyperpolarizations and relaxations were sensitive to gap junction blockers and these arteries expressed more endothelial and myoendothelial gap junctions than arteries from SHRs. Responses in WKY rats but not SHRs were also reduced by inhibitors of epoxyeicosatrienoic acids (EETs) 14 15 with Bonferroni modification for multiple groups as appropriate. Data are presented as means ± S.E.M. Numbers represent preparations each taken from a different rat. A value < 0.05 was taken to denote significance. Results Blood pressure of SHRs was significantly higher than that of WKY rats (SHRs 196 ± 3 mm Mouse monoclonal to CD81.COB81 reacts with the CD81, a target for anti-proliferative antigen (TAPA-1) with 26 kDa MW, which ia a member of the TM4SF tetraspanin family. CD81 is broadly expressed on hemapoietic cells and enothelial and epithelial cells, but absent from erythrocytes and platelets as well as neutrophils. CD81 play role as a member of CD19/CD21/Leu-13 signal transdiction complex. It also is reported that anti-TAPA-1 induce protein tyrosine phosphorylation that is prevented by increased intercellular thiol levels. Hg = 16; LY2886721 WKY rats 137 ± 4 mm Hg = 11; < 0.05). Treatment of SHRs with enalapril successfully reduced blood pressure (117 ± 3 mm Hg = 21; < 0.05 one-way ANOVA). Blood pressure of enalapril-treated SHRs was significantly lower than that of WKY rats. Role of KCa Channels in EDHF Responses. Maximal constrictions to phenylephrine (0.1-10 μM) were significantly greater in SHRs than in enalapril-treated counterparts and WKY rats although the sensitivity did not differ between the different rat groups (maximal constrictions and p= 4 ACh (0.001-3 μM) reversed the constriction produced by submaximal concentrations of phenylephrine (0.3-1 μM) in all three rat groups without significant difference in p= 34; SHRs -7.8 ± 0.1 97.3 ± 0.7% = 24; SHR + enalapril -7.8 ± 0.1 97.7 ± 1.0% = 18). To determine whether differences existed in the time course of dilation among the groups the sustained response that persisted after the initial peak response was also analyzed. No significant difference was found in p= 25; SHRs -7.8 ± 0.1 98.4 ± 2.1% = 21; SHR + enalapril -7.7 ± 0.1 98.7 ± 2.6% = 18). In the absence or presence of phenylephrine (1 μM) the resting membrane potential of smooth muscle cells was not significantly different among the three rat groups phenylephrine producing approximately 10-mV depolarization (Table 1). ACh (1 μM) induced a hyperpolarization in all three groups. The amplitude of hyperpolarization in SHRs was significantly smaller than in WKY rats but was restored in enalapril-treated SHRs to values comparable with those in WKY rats (Table 1). TABLE 1 Resting membrane potential measurements (RMP) in control and in ACh in the presence and absence of phenylephrine Both levcromakalim (KATP opener) and 1-EBIO (IKCa LY2886721 channel opener) caused concentration-dependent hyperpolarizations and relaxations that did not differ between WKY rats and SHRs (p= 4; SHRs -6.8 ± 0.2 = 4; hyperpolarizations to 10 μM: WKY rats -27 ± 1.5 mV = 4; SHRs -27 ± 1.4 mV = 4; p= 4; SHRs -4.4 ± 0.2 = 4; hyperpolarizations to 300 μM: WKY rats -19 ± 0.9 mV = 3; SHRs -18 ± 3.5 mV = 3) indicating no impairment in the ability of either smooth muscle or endothelial K channels respectively to elicit hyperpolarization and relaxation. Blockers of calcium-activated potassium channels namely the SKCa (apamin 500 nM) and IKCa (TRAM-34 500 nM) in the presence of 10 μM ODQ significantly shifted ACh curves to the right in all three rat groups. Addition of the large-conductance KCa blocker IbTx (100 LY2886721 nM) abolished relaxations although a small residual relaxation persisted in the WKY group (Fig. 1 Fig. LY2886721 1. Role of calcium activated potassium channels in EDHF responses. ACh-induced dilations in mesenteric artery from WKY rats SHRs and enalapril-treated SHRs were significantly attenuated by apamin (500 nM) TRAM-34 (500 nM) ODQ (10 μM) and … Immunohistochemical staining for SKCa IKCa and BKCa channels demonstrated that the channels were differentially distributed between the endothelium and smooth muscle; there is no difference in expression among the rat groups however. SKCa expression Thus.