Figure 1.
Plasma EO and BP are elevated following a 14 day icv Ang II infusion: role of central mineralocorticoid receptors and aldosterone synthase.
Panel A, plasma EO. Panel B, mean arterial blood pressure. C = vehicle control; A = Ang II; A+E = Ang II + eplerenone; A+F = Ang II + FAD-286; *P<0.01 vs all other groups; n = 7–8/group.
Figure 2.
Increased expression of arterial Ca2+ transport proteins following a 14 day icv Ang II infusion.
Panels A, B and C, representative Western blots and summary data for NCX1, TRPC6 and SERCA2 expression, respectively, in de-endothelialized aorta. Blots were normalized for β-actin as a loading control and the changes shown are relative to the control group. All lanes were loaded with 10–20 µg of membrane protein. The expected molecular weights are: NCX1, 116 KDa; TRPC6, 111 KDa, SERCA2 115 KDA, and β-actin, 42 KDa. C = vehicle control; A = Ang II; A+E = Ang II + eplerenone; A+F = Ang II + FAD-286; *P<0.01 vs all other groups; n = 7–8/group. Summary data are from 4 blots for each protein.
Figure 3.
Summary analysis of the effects of CNS Ang II infusion on plasma EO based upon SPE-LC-RIA data.
Ouabain immunoreactivity in LC separated plasma pools from controls (A), icv Ang II (B), icv ANG II + eplerenone (C), and icv Ang II + FAD286 infused rats (D). In each case EO eluted in fraction 35 (black bar). Other immunoreactive materials are shown in the gray bars. Dashed red lines in A–D are the values from the control for comparison. Dashed lines represent 5% threshold for the RIA under the conditions used. Only peaks that exceeded the thresholds are shown. Ouabain immunoreactivity in LC separated plasma pools arranged by study group. Response of: total ouabain immunoreactivity (E), Isomer 1 (F), EO (G), and Isomer 2 (H). Study groups: C, icv vehicle. A, icv Ang II. A+E, icv Ang II + eplerenone. A+F, icv Ang II + FAD 286.
Figure 4.
Summary analysis of plasma EO and isomers in response to CNS Ang II infusion based upon SPE-LC-MS3 data.
In each case, the relative spectral intensities at m/z 379.2 are shown normalized to the DHO reference at m/z 381.2 for each of the LC fractions. The study groups were: A; Controls. B; icv Ang II infused. C; icv Ang II + eplerenone. D; icv Ang II + FAD286. The dashed lines in each plot represent the thresholds for detection (i.e., >3x ambient signal to noise ratio).
Table 1.
Adrenal and Pituitary Levels of EO.
Figure 5.
Proposed scheme for the chronic pressor action of central Ang II in the rat.
A. Summary of prior ideas in which the links between icv Ang II and elevated BP were mediated by activation of angiotensin type I receptors (AT1R), increases in sympathetic nervous system activity (SNA), and elevated plasma levels of AVP and ACTH [2]–[5]. B. Revised model presenting a pathway involving the CNS, humoral and vascular events that may link activation of hypothalamic AT1R with hypertension as suggested by the present and related studies. The CNS component involves amplification of chronic Ang II mediated signaling via local stimulation of mineralocorticoid receptors (MR) by aldosterone and increased brain and circulating EO [14]. The CNS effects of Ang II raise SNA and plasma EO; the latter reprograms arterial myocyte function leading to: a) Increased Ca2+ and Na+ entry via NCX1 and TRPC6, and increased intracellular Ca2+ stores via SERCA2 [29], [54]–[56], [59]. b) Amplification of SNA in the sympathetic ganglia and vascular wall [60], [61] and, c) increased myogenic and evoked tone, and elevated TPR and BP [43], [71]. A central MR antagonist blocks all measured downstream effects of icv Ang II. The increased SNA and vascular reprogramming together appear to underlie the elevated BP. AVP, plasma arginine vasopressin. ACTH, adrenocorticotropic hormone. MT, myogenic tone. TPR, total peripheral resistance. See text for references and abbreviations not listed here.