Tonin Overexpression in Mice Diminishes Sympathetic Autonomic Modulation and Alters Angiotensin Type 1 Receptor Response

Figure 1. Hemodynamic evaluation in wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)] at baseline and after angiotensin type 1 receptor blocker, losartan: Overexpression of tonin enzyme increased the systolic (A) and diastolic (B) blood pressure (BP, p = 0.0464) without significant changes in the heart rate (HR, C). Blockage of AT1R reduced systolic and diastolic BP in both strains (p = 0.0036). Mice given losartan maintained similar HR to baseline. N = 4, Two-way ANOVA *p < 0.05, followed by bonferroni post hoc, bar graphs are means ±SEM.

Figure 2. Time and frequency domain evaluation of heart rate (HR) variability in wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)] at baseline and after angiotensin type 1 receptor blocker, losartan: Variance of pulse interval (VAR PI) (A) low frequency band of pulse interval (LF PI), including absolute (B), percent (C), and normalized units (D), high frequency of pulse interval (HF PI) including absolute (E), percent (F), and normalized units (G), sympathovagal balance (LF/HF) (H). LF bands represent the sympathetic modulation whereas HF parasympathetic. N = 4, Two-way ANOVA followed by bonferroni post hoc *p < 0.05, bar graphs are means ±SEM.

Figure 3. Time and frequency domain evaluation of blood pressure variability in wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)] at baseline and after angiotensin type 1 receptor blocker, losartan: Variance of SBP (VAR SBP) (A), low frequency band of SBP (LF SBP) (B) and alpha index (C). LF bands represent sympathetic modulation and alpha index represents baroreflex sensitivity. N = 4, Two-way ANOVA followed by bonferroni post hoc *p < 0.05, bar graphs are means ±SEM.

Figure 4. Angiotensin content in three chambers of the heart in wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)]: Heart angiotensin concentration of WT and TGM'(rTon) mice were quantified by High Performance Liquid Chromatography. AngI, AngII, and Ang1-7 were measured in each chamber. N = 4, Two-way ANOVA followed by multiple t-tests *p < 0.05, bar graphs are means ±SEM.

Figure 5. Total AngI, AngII, and Ang1-7 formation activity in atria, right ventricle and left ventricle of wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)]: AngI levels in the atria after incubation with tetradecapeptide as substrate at 0, 10, 20, 40, 60, 120, 240, 360, and 1,440 min (n = 2) (A). AngI (B), AngII (C), and Ang1-7 (D) in the right ventricle (RV) after incubation with tetradecapeptide as substrate at 0, 10, 20, 40, 60, 120, 240, 360, and 1,440 min by LC-MS/MS (n = 4). Ang1-7 (E) levels in the left ventricle (LV) after incubation with AngII as substrate at 0, 10, 20, 40, 60, 120, 240, 360, and 1,440 min by LC-MS/MS (n = 4). Multiple t-tests were performed, *p < 0.05, **p < 0.001 time points are represented by means ± SEM.

Figure 6. Total Ang I, Ang II, and Ang1-7 formation in the plasma of wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)]: AngI (A), AngII (B), and Ang1-7 (C) in the plasma (PL) after incubation with tetradecapeptide as substrate at 0, 10, 20, 40, 60, 120, 240, 360, and 1,440 min by LC-MS/MS (n = 4). Multiple t-test were performed *p < 0.05, time points are represented by means ±SEM.

Figure 7. Total Ang II and Ang1-7 formation in the plasma of wild type (WT) and transgenic mice overexpressing rat tonin [TGM'(rTon)]: AngII (A) and Ang1-7 (B) in the plasma (PL) after incubation with AngI as substrate at 0, 10, 20, 40, 60, 120, 240, 360, and 1,440 min by LC-MS/MS (n = 4). Ang1-7 (C) in the plasma after incubation with AngII (n = 4–5). Multiple t-test were performed *p < 0.05, time points are represented by means ± SEM.