Reduced expression of PMCA1 is associated with increased blood pressure with age which is preceded by remodelling of resistance arteries

Figures

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  Figure 1. PMCA1Ht mice display reduced PMCA1 expression. (A) Protein expression of PMCA1 was reduced in tissues from 6‐month‐old PMCA1Ht mice. Ai. Western blots (PMCA1 at 143KDa and GAPDH at 50KDa) and Aii. quantification of PMCA1 normalized to GAPDH in WT and Ht mice. n = 3 & 3. (t‐test for each tissue). (B) Aortic mRNA expression of Atp2b1, presented relative to young WT, was significantly reduced in 6‐month‐old (n = 8 & 7) and in 18‐month‐old (n = 4 & 6) PMCA1Ht mice (P < 0.0001). No significant effect of age or interaction was determined (P = 0.050 and P = 0.925 respectively, 2‐way ANOVA). (C) Aortic mRNA expression of Atp2b4, presented relative to young WT, was not significantly reduced in 6 months (n = 8 & 7) or in 18‐month‐old (n = 4 & 6) PMCA1Ht mice (P = 0.714), although a significant effect of age was determined (P = 0.0003, 2‐way ANOVA). (D) Detection of primary antibody against PMCA1 in aorta from 6‐month‐old WT Di. and PMCA1Ht Dii. mice. Diii. Staining of aorta when primary antibody omitted. Div. Staining of aorta with DAB reagent only. Scale bar represents 100 μm. E. mRNA expression of Atp2b1 was significantly reduced in endothelial cells isolated from lungs of 6‐month‐old…

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  Figure 2. Conscious BP increases with age in PMCA1Ht mice. (A) Conscious peripheral BP (Systolic, Ai. and diastolic, Aii.) of PMCA1Ht mice is significantly higher at 12 months and then at all older ages (t‐test vs. age‐matched WT, n = 5–7). (B) No significant difference in conscious pulse rate is recorded in young or aged PMCA1Ht mice (P = 0.290, and P = 0.972 for interaction. Two‐way ANOVA) n = 5, 5, 7 & 6. (C) Arterial BP (Systolic, Ci. and diastolic, Cii.) of 6‐month‐old animals, under anaesthesia, does not significantly differ between WT and PMCA1Ht mice (t‐test, n = 10 & 12). Mean value ± SEM. **P < 0.01, ***P < 0.001.

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  Figure 3. Remodelling of small mesenteric arteries occurs with age in PMCA1Ht mice and before a detectable increase in BP. (A) The internal lumen diameter does not significantly differ between passive mesenteric arteries from WT and PMCA1Ht mice at 6 months of age but is significantly smaller in PMCA1Ht mice at 9 and 18 months (B & C). (D) Wall thickness is similar at 6 months of age and significantly increases with age in PMCA1Ht arteries (E & F). (G, H. and I) The vessel wall thickness to lumen ratio (W:L) is significantly increased in arteries from PMCA1Ht mice aged 6, 9 and 18 months old. (J, K and L) The cross‐sectional area (CSA) of the vessel wall is not significantly different between arteries taken from WT and PMCA1Ht mice at any age tested. Extra sum of squares F‐test analysis was performed. All data were plotted as mean value ± SEM. n = 4–8 *P < 0.05, **P < 0.01, ***P < 0.001.

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  Figure 4. Stiffness of resistance arteries increases with age but is not significantly altered in arteries from PMCA1Ht mice. (A) Stress–strain relationship derived from passive properties shows leftward shift for arteries from 6‐month‐old mice to 18‐month‐olds. (B) The distensibility of arteries from PMCA1Ht mice is not significantly different (P = 0.215) from arteries of WT mice as shown by incremental elastic modulus. A significant increase in age was detected (P = 0.022) between arteries from 6‐ and 18‐month‐old animals. No significant interaction was determined (0.326) when analysing these 2 ages. Two‐way ANOVA with Bonferroni post hoc test. Mean ± SEM. n = 5–8. *P < 0.05.

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  Figure 5. Arteries from PMCA1Ht mice contract similarly but display elevated myogenic tone and basal intracellular calcium. (A & B) The magnitude of contraction to a depolarizing stimulus (100 mM K+) is not significantly different for arteries from PMCA1Ht mice for both young (A. P = 0.773. n = 6 & 7) and aged (B. P = 0.334. n = 7 & 6) animals (t‐test). C & D. Arteries from PMCA1Ht mice do not display a significant difference in contractility to noradrenaline (NA) from both young (C. P = 0.537. n = 6 & 6) and aged (D. P = 0.162. n = 4 & 6) animals (Nonlinear regression comparison of fits). (E and F) Arteries from PMCA1Ht mice display significantly elevated myogenic tone in both young (E. n = 5 & 5) and aged (F. n = 6 & 6) animals (comparison of fit analysis). G. & H. A significantly elevated arterial indo‐1 F400/F500 emission ratio, indicative of intracellular free Ca2+ concentration, was detected at both ages (G & H, young and old, respectively. n = 5 & 7 and 7 & 5). All data were plotted as mean value ± SEM. *P < 0.05, **P < 0.01.