Sympathetic-renal interaction in chronic arterial pressure control

Abstract

The effects of neonatal sympathectomy of donors or recipients on posttransplantation arterial pressure were investigated in spontaneously hypertensive rats (SHR) by renal transplantation experiments. Conscious mean arterial pressure (MAP) and renal vascular resistance were 136 +/- 1 mmHg and 15.5 +/- 1.2 mmHg x ml(-1) x min x g in sympathectomized SHR (n = 8) vs. 158 +/- 4 mmHg (P < 0.001) and 20.8 +/- 1.1 mmHg x ml(-1) x min x g (P < 0.05) in controls (n = 10). Seven weeks after transplantation of a kidney from neonatally sympathectomized SHR donors, MAP in SHR recipients (n = 10) was 20 mmHg lower than in controls transplanted with a kidney from hydralazine-treated SHR (n = 10) (P < 0.05) associated with reduced sodium sensitivity of MAP. Neonatal sympathectomy also lowered MAP in F1-hybrids (F1H; SHR x Wistar-Kyoto rats). Within 6 wk after transplantation, renal grafts from untreated SHR increased MAP by 20 mmHg in sympathectomized F1H (n = 10) and by 35 mmHg in sham-treated F1H (n = 8) (P < 0.05). Neonatal sympathectomy induces chronic changes in SHR kidney function leading to a MAP reduction even when extrarenal sympathetic tone is restored. Generalized reduction in sympathetic tone resets the kidney-fluid system to reduced MAP and blunts the extent of arterial pressure rise induced by an SHR kidney graft.

The Kidney as a Determinant of Genetic Hypertension

“…Thus, SHR recipients of an SHR kidney graft from neonatally sympathectomized donors had an Ϸ20 mm Hg lower mean arterial pressure than SHR recipients of an SHR kidney graft from hydralazine-treated control donors. 21 Furthermore, SHR kidney grafts increased mean arterial pressure by only Ϸ20 mm Hg in neonatally sympathectomized F1 hybrids compared with Ϸ35 mm Hg in untreated F1 hybrids. 21 Together, these data indicate that the sympathetic nervous system contributes to hypertension in SHR via its actions on the kidney and nonrenal tissues.…”

“…21 Furthermore, SHR kidney grafts increased mean arterial pressure by only Ϸ20 mm Hg in neonatally sympathectomized F1 hybrids compared with Ϸ35 mm Hg in untreated F1 hybrids. 21 Together, these data indicate that the sympathetic nervous system contributes to hypertension in SHR via its actions on the kidney and nonrenal tissues. The kidney-mediated long-term effects on blood pressure of the sympathetic nervous system can be transmitted with the kidney to renal graft recipients.…”

Neonatal sympathectomy reduces NADPH oxidase activity and vascular resistance in spontaneously hypertensive rat kidneys

“…We previously showed lower arterial pressure in SHR transplanted with a kidney from a sympathectomized SHR donor than in SHR recipients of a kidney from a hydralazine-treated SHR donor (14). In addition, Na ϩ sensitivity of arterial pressure was lower in recipients of a kidney graft from sympathectomized donors than in recipients of a graft from hydralazine-treated donors (14). The present study was performed to identify mechanisms that may explain these findings; therefore, we focused on kidneys from sympathectomized and hydralazine-treated SHR.…”

“…Arterial pressure can be chronically lowered in SHR by neonatal sympathectomy (19,21), and renal mechanisms are involved in this chronic arterial pressure reduction (14). We previously showed lower arterial pressure in SHR transplanted with a kidney from a sympathectomized SHR donor than in SHR recipients of a kidney from a hydralazine-treated SHR donor (14). In addition, Na ϩ sensitivity of arterial pressure was lower in recipients of a kidney graft from sympathectomized donors than in recipients of a graft from hydralazine-treated donors (14).…”

“…We found that NADPH oxidase activity was reduced in the renal cortex and medulla of young sympathectomized SHR. Therefore, we tested whether this reduction of renal NADPH oxidase activity is associated with chronic changes in renal function that would persist in transplanted kidneys and may help explain the long-term renal effects of neonatal sympathectomy on arterial pressure in SHR (14).…”