Renal denervation modulates angiotensin receptor expression in the renal cortex of rabbits with chronic heart failure

Abstract

Excessive sympathetic drive is a hallmark of chronic heart failure (HF). Disease progression can be correlated with plasma norepinephrine concentration. Renal function is also correlated with disease progression and prognosis. Because both the renal nerves and renin-angiotensin II system are activated in chronic HF we hypothesized that excessive renal sympathetic nerve activity decreases renal blood flow in HF and is associated with changes in angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R) expression. The present study was carried out in conscious, chronically instrumented rabbits with pacing-induced HF. We found that rabbits with HF showed a decrease in mean renal blood flow (19.8±1.6 in HF vs. 32.0±2.5 ml/min from prepace levels; P<0.05) and an increase in renal vascular resistance (3.26±0.29 in HF vs. 2.21±0.13 mmHg·ml(-1)·min in prepace normal rabbits; P<0.05) while the blood flow and resistance was not changed in HF rabbits with the surgical renal denervation. Renal AT1R expression was increased by ∼67% and AT2R expression was decreased by ∼87% in rabbits with HF; however, kidneys from denervated rabbits with HF showed a near normalization in the expression of these receptors. These results suggest renal sympathetic nerve activity elicits a detrimental effect on renal blood flow and may be associated with alterations in the expression of angiotensin II receptors.

Fig. 1.

Representative timeline for the animals used in this study. Protocol 1 focused on the in vivo measurements (10 animals); protocol 2 focused on the validation of the denervation (DnX) maneuver (17 animals); and protocol 3 focused on the analysis of renal receptor expression (19 animals). Some animals were used in more than one protocol (see the text).

Fig. 2.

Original recordings (protocol 1). All panels represent a 5-s recording of baseline hemodynamics. A: prepace intact animal. B: the same animal as in A after 3 wk of continuous ventricular pacing. C: is a prepace DnX animal. D: the same animal as in C after 3 wk of continuous pacing. AP, arterial pressure; MAP, mean arterial pressure; HR, heart rate; RBF, renal blood flow; mRBF, mean renal blood flow; RVR, renal vascular resistance. EF indicates the ejection fraction of the rabbit on the day of the recording.

Fig. 3.

Renal hemodynamics (protocol 1). A: RBF was measured via flow probe around the left renal artery in 5 intact and 5 DnX animals before and after 3 wk of continuous pacing The value for 1 animal is the average of a 10-min recording on 3 separate days. †P < 0.05 vs. respective prepace group. ‡P < 0.05 vs. postpace; n = 5. B: RVR in 5 intact and 5 DnX animals before and after the pacing protocol. The value for 1 animal is the average of a 10-min recording on 3 separate days. †P < 0.05 vs. respective prepace group. ‡P < 0.05 vs. postpace; n = 5.

Fig. 4.

Validation of DnX (protocol 2). Shown is percent change in RBF in response to oropharyngeal smoke before and after pacing in intact (n = 5) and renal DnX animals (n = 5). *P < 0.05, postpace vs. prepace intact group. †P < 0.05 DnX vs. intact group.

Fig. 5.

Angiotensin receptor expression in kidney microvasculature (protocol 3). A: ANG II type 1 receptor (AT1R) was measured in a microvessel-enriched lysate obtained from 4 separate groups of animals (see materials and methods) and normalized to the loading control GAPDH. †P < 0.05 vs. respective nonpaced group. ‡P < 0.05 vs. postpace; n = 5 except n = 4, nonpaced DnX. B: ANG II type 2 receptor (AT2R) was measured in a microvessel-enriched lysate obtained from 4 separate groups of animals (see materials and methods) and normalized to the loading control GAPDH. †P < 0.05 vs. respective nonpaced group. ‡P < 0.05 vs. postpace; n = 5 except n = 4, nonpaced DnX. Arrows denote bands representing AT1R (A) and AT2R (B). Presence of the doublet at the site of the band of interest is likely detection of a posttranslational modification of the receptor. Fainter bands detected are likely nonspecific binding or protein fragments.

Fig. 6.

Relative balance of angiotensin receptor expression in kidney microvasculature (protocol 3). Shown is the balance of AT1R to AT2R expression in the 4 groups of rabbits studied. †P < 0.05 vs. respective nonpaced group. ‡P < 0.05 vs. postpace; n = 5 except n = 4, nonpaced DnX.