Calcimimetic R-568 vasodilatory effect on mesenteric vascular beds from normotensive (WKY) and spontaneously hypertensive (SHR) rats. Potential involvement of vascular smooth muscle cells (vSMCs)

Figures

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  Fig 1. Vascular effects of R-568 in MVB from WKY and SHR rats. Mesenteric vascular beds (MVB) from 8-week old WKY and SHR rats were isolated and prepared as described in Methods. PP at approximately 120 mmHg was maintained by continuous infusion with NA (10 μM and 3 μM in WKY and SHR rats, respectively). (A) and (B) Representative tracings of vasodilator responses to submaximal ACh dose (1 μM) and to increasing concentrations of R-568 (10 nM—30 μM) in WKY (A) and SHR (B) are shown. Each symbol represents the start of a 4-min perfusion. (C) Dose-response curves for R-568-induced vascular effects were obtained from MVB of WKY and SHR. Results are the mean ± SEM of 7 (WKY) and 6 (SHR) independent experiments. Data from each curve were normalized by defining 100% as the initial steady state PP and 0% as the maximal reduction in PP obtained in WKY treated with 1 μM ACh. *p < 0.01 vs respective values.

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  Fig 2. Evaluation of endothelial mediators involved in vascular effects of R-568 in MVB from WKY and SHR rats. (A) and (B) Representative tracings of vascular response to R-568 (10 nM—30 μM) in MVB from WKY (A) or SHR (B) pretreated with L-NAME, CTX and INDO are shown. Each symbol represents the start of a 4-min perfusion. (C) MVB isolated from 8-week old WKY (closed symbols) were stimulated with increasing concentrations of R-568 in the absence (circles) or in the presence of L-NAME (100 μM/20 min; squares), L-NAME+CTX (300 nM/20 min; triangles), L-NAME+CTX+INDO (10 μM/20 min; diamonds). Results are the mean ± SEM of 4 WKY independent experiments. (D) MVB isolated from 8-week old SHR (open symbols) were stimulated with increasing concentrations of R-568 in the absence (circles) or in the presence of L-NAME (100 μM/20 min; squares), L-NAME+CTX (300 nM/20 min; triangles), L-NAME+CTX+INDO (10 μ M/20 min; diamonds). Results are the mean ± SEM of 4 WKY and 4 SHR independent experiments. *p < 0.04 and #p < 0.05 vs respective CTRL curve.

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  Fig 3. Effect of endothelium removal and CaSR inhibition on vascular response to R-568. (A) MVB isolated from 8-week old WKY (closed symbols) and SHR (open symbols) were stimulated with increasing concentrations of R-568 in the presence (circles) or in the absence (squares) of endothelium. Results shown are the mean ± SEM of 3 (WKY) and 3 (SHR) independent experiments. Data from each curve were normalized as in Fig 1. (B) MVB isolated from 8-week old WKY (closed symbols) and SHR (open symbols) were stimulated with increasing concentrations of R-568 in the absence (circles) or after pretreatment with (diamonds) Calhex-231 (3 μM/20 min). Results are the mean ± SEM of 3 WKY and 3 SHR independent experiments. Data from each curve were normalized as in Fig 1. *p < 0.05 vs respective CTRL curve.

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  Fig 4. Evaluation of signaling pathways activated by R-568 in MVB from WKY and SHR. MVB homogenates from experiments described in Fig 1 were subjected to immunoblotting for total and phosphorylated forms of Akt (phospho-AktSer473), and eNOS (phospho-eNOSSer1177). Total β-actin levels were used as loading control. A representative set of immunoblots is shown for experiments that were repeated independently 3 times. Each bar represents the mean ± SEM of densitometric analysis for phosphorylated proteins normalized to their respective total forms. *p < 0.05 vs respective basal.

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  Fig 5. CaSR expression in WKY- and SHR-vSMVCs. (A) Representative morphometric aspect of confluent vSMC cultures from normotensive rats (WKY) and spontaneously hypertensive rats (SHR) (magnification x 10; scale bar: 300 μM). The cells were plated and morphologically examined three different times in the same experimental conditions. (B) Representative pattern of electrophoretic bands (170–100, 70–55 and 40–25 kDa) that results from immunoblotting analysis of CaSR expression in WKY- and SHR-vSMCs lysates and its negative (NC, HEK293 empty vector transfected control cell lysate) and positive (PC, HEK293 CaSR transiently transfected cell lysate) controls. (C) Representative images of α-SMA flow cytometry analysis in WKY-and SHR-vSMCs and secondary antibody alone (control).

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  Fig 6. Effect of R-568 on Akt activation and NO production in vSMCs from WKY and SHR rats. (A) vSMCs stimulated with 1μM of R568 (R) at different times (30 seconds, 1 minute, 2 minutes) in the presence or absence of Calhex 231 (C, 1 μM) were subjected to immunoblotting for total and phosphorylated forms of Akt (phospho-AktSer473). Total β-actin levels were used as loading control. A representative set of immunoblots is shown for experiments that were repeated independently 3 times. Each bar represents the mean ± SD of densitometric analysis for phosphorylated proteins normalized to their respective total forms. *p < 0.02 vs respective basal (CTRL), **p < 0.05 R+C vs respective R. (B) NO production determined by conversion of L-[3H]-arginine into L-[3H]-citrulline in vSMCs stimulated with 1μM of R568 in the presence or absence of Calhex 231 (1 μM), data are expressed as pmol/NO/min/mgprottot (picomoles /Nitric Oxide/ minutes/ milligrams protein total). Each bar represents the mean ± SD of 3 independent experiments. *p < 0.02 R568 vs respective basal, **p < 0.01 R568+Calhex vs respective R568.