Key result
In uninephrectomized dogs, intrarenal norepinephrine infusion increased mean arterial pressure from 95.6 to 115.7 mm Hg, independent of extracellular fluid volume expansion.
Why the study?
Does low-level intrarenal norepinephrine infusion produce sustained arterial hypertension independent of extracellular fluid volume expansion in uninephrectomized dogs?
Does low-level intrarenal norepinephrine infusion produce sustained arterial hypertension independent of extracellular fluid volume expansion in uninephrectomized dogs?
Low-level elevation of intrarenal norepinephrine produces sustained arterial hypertension independent of extracellular fluid volume expansion, suggesting increased renal vascular sensitivity to norepinephrine.
Animal data implicate intrarenal norepinephrine in hypertension; leaves open translation to human disease and practice.
Individuals with essential hypertension have been characterized by increased renal sympathetic vascular tone with decreased plasma volume and normal cardiac output compared with normotensive individuals. We used a servo-controlled intrarenal infusion system to evaluate the hemodynamic, renal excretory, and plasma hormonal responses to 28-day, low-level elevations in the intrarenal adrenergic neurotransmitter norepinephrine. In uninephrectomized dogs (n = 6), servo-controlled norepinephrine infusion increased mean arterial pressure from 95.6 +/- 3.1 to 115.7 +/- 4.9 mm Hg on day 1 without concomitant reductions in renal blood flow. Arterial hypertension was sustained and renal vascular resistance increased during the 28 days of servo-controlled norepinephrine infusion despite significant decreases in the daily dose of intrarenal norepinephrine (1.49 +/- 0.23 to 0.47 +/- 0.25 mg/d) necessary to maintain renal blood flow constant. Arterial pressure returned to control values with the cessation of servo-controlled norepinephrine, whereas renal blood flow and renal vascular resistance remained slightly decreased and increased, respectively. Cumulative sodium balance exhibited a net 177 +/- 37 mmol sodium loss over the 28 days of norepinephrine infusion, indicating that the hypertension did not result from sodium retention or expansion of extracellular fluid volume. Intrarenal norepinephrine did not change plasma epinephrine, norepinephrine, or vasopressin concentrations. Atrial natriuretic factor, however, increased at 7 and 14 days of servo-controlled norepinephrine, and plasma renin activity increased on day 14 of norepinephrine infusion. We conclude that low-level elevation of intrarenal adrenergic neurotransmitter produces sustained arterial hypertension that is independent of expansion in extracellular fluid volume, increases in circulating catecholamines or plasma renin activity, or reductions in renal blood flow. This hypertension may be associated with increased renal vascular sensitivity to norepinephrine and/or other renal vasoactive factors.
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Plato et al. (1996) studied Hypertension (n=6). Intrarenal norepinephrine infusion vs. Baseline was evaluated on Mean arterial pressure. In uninephrectomized dogs, intrarenal norepinephrine infusion increased mean arterial pressure from 95.6 to 115.7 mm Hg, independent of extracellular fluid volume expansion.
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