Objective—To determine norepinephrine (NE) kinetics
in dogs with experimentally induced renal vascular
Animals—4 mixed-breed dogs.
Procedure—The study comprised a control and
hypertensive period. The hypertensive period followed
induction of renal vascular hypertension
achieved by surgical placement of clips on both renal
arteries to reduce diameter by approximately 80%.
Arterial blood pressure, renal clearance, and NE kinetics
were measured during each period while dogs
were receiving a low-sodium diet. Measurements of
NE kinetics and renal clearance during the hypertensive
period were made 5 days after induction of
Results—Five days after induction of hypertension,
arterial blood pressure increased by 15 to 20 mm Hg.
Mean (± SEM) plasma NE concentration and NE
spillover rate increased significantly from 151.5 ± 14.1
pg/ml and 8.03 ± 0.62 ng/kg/min, respectively, during
the control period to 631.4 ± 30.5 pg/ml and 54.0 ± 5.2
ng/kg/min, respectively, during the hypertensive period.
Norepinephrine clearance rate also increased (54.0
± 2.4 vs 86.0 ± 9.3 ml/kg/min). Positive associations
between mean arterial pressure (MAP) and NE concentration
and spillover rate were detected. However,
MAP and NE clearance rate were not associated.
Conclusions and Clinical Relevance—Increased
blood pressure during the hypertensive period was
likely attributable to increased NE spillover rate, which
resulted in a significant increase in plasma NE concentration.
Analysis of these results suggests that
central sympathetic outflow was increased and may
be responsible for the pathogenesis of high blood
pressure during the acute phase of renal vascular
hypertension in dogs. (Am J Vet Res 2000;61:
Objective—To determine effects of variations in
dietary intake of sodium chloride (NaCl) on systemic
arterial blood pressure (ABP) in cats with normal and
reduced renal function.
Animals—21 adult cats (7 with intact kidneys [control
cats; group C], 7 with unilateral renal infarction with
contralateral nephrectomy [remnant-kidney model;
group RK], and 7 with unilateral renal infarction and
contralateral renal wrapping and concurrent oral
administration of amlodipine [remnant-wrap model;
Procedure—All cats were sequentially fed 3 diets
that differed only in NaCl content (50, 100, or 200 mg
of Na/kg); each diet was fed for 7 days. The ABP was
recorded continuously by radiotelemetry, and renal
function (glomerular filtration rate [GFR]) was determined
on the sixth day of each feeding period.
Results—Dietary supplementation with NaCl did not
affect ABP, but it increased GFR in groups C and WA.
The renin-angiotensin-aldosterone axis was activated
in groups RK and WA at the lowest NaCl intake, but
supplementation with NaCl suppressed this activation
in group WA. The lowest NaCl intake was associated
with hypokalemia and a high fractional excretion
of potassium that decreased in response to supplementation
with NaCl. Arterial baroreceptor resetting
was evident after chronic hypertension but was not
modified by dietary supplementation with NaCl.
Conclusions and Clinical Relevance—Low NaCl
intake was associated with inappropriate kaliuresis,
reduced GFR, and activation of the renin-angiotensinaldosterone
axis without evidence of a beneficial
effect on ABP. Therefore, this common dietary maneuver
could contribute to hypokalemic nephropathy and
progressive renal injury in cats. ( Am J Vet Res 2004;65:620–627)