Objective—To compare glomerular filtration rate
(GFR) measured via urinary clearance of inulin (UCI)
with plasma clearance of technetium Tc 99m pentetate
(99mTc-pentetate) and creatinine in dogs.
Animals—6 healthy Beagles and 18 Beagles with
reduced renal function.
Procedure—13 blood samples were obtained
between 5 and 600 minutes after IV bolus injections
of 99mTc-pentetate and creatinine. Plasma clearance of
99mTc-pentetate was computed on the basis of 1, 2, or
13 samples, and plasma clearance of creatinine was
computed on the basis of 2, 5, or 13 samples. During
plasma clearance procedures, constant IV infusion of
carboxyl carbon 14 inulin was begun and UCI was
determined in urine collected from 90 to 120, 120 to
180, and 180 to 240 minutes. Clearance procedures
were repeated in 12 dogs to evaluate reproducibility
Results—Significant association between UCI and
plasma clearance was determined via all methods.
However, plasma clearances were moderately to
markedly different from UCI, depending on test substance,
GFR, and sample numbers used for plasma
clearance computations. Comparisons were particularly
discordant when some methods of limiting samples
were used to define plasma clearance.
Conclusions and Clinical Relevance—Values
derived from plasma clearance methods for 99mTc-pentetate
and creatinine were not interchangeable with
UCI results, which raises questions about their reliability
as clinical research tools for measurement of
GFR. Plasma clearance methods that are relative
indices of renal function should not be interpreted as
accurate measures of GFR without validation. (Am J Vet Res 2005;66:1046–1055)
Objective—To determine whether pharmacokinetic
analysis of data derived from a single IV dose of
iohexol could be used to predict creatinine clearance
and evaluate simplified methods for predicting serum
clearance of iohexol with data derived from 2 or 3
blood samples in clinically normal foals.
Animals—10 healthy foals.
Procedure—Serum disposition of iohexol and exogenous
creatinine clearance was determined simultaneously
in each foal (5 males and 5 females). A 3-compartment
model of iohexol serum disposition was
selected via standard methods. Iohexol clearance calculated
from the model was compared with creatinine
clearance. Separate limited-sample models were
created with various combinations of sample times
from the terminal slope of the plasma versus time
profile for iohexol. Correction factors were determined
for the limited-sample models, and iohexol
clearance calculated via each method was compared
with exogenous creatinine clearance by use of
method comparison techniques.
Results—Mean exogenous creatinine clearance was
2.17 mL/min/kg. The disposition of iohexol was best
described by a 3-compartment open model. Mean
clearance value for iohexol was 2.15 mL/min/kg and
was not significantly different from mean creatinine
clearance. A method for predicting serum iohexol
clearance based on a 2-sample protocol (3- and 4-hour
samples) was developed.
Conclusions and Clinical Relevance—Iohexol clearance
can be used to predict exogenous creatinine
clearance and can be determined from 2 blood samples
taken after IV injection of iohexol. Appropriate
correction factors for adult horses and horses with
abnormal glomerular filtration rate need to be determined.
(Am J Vet Res 2003;64:1486–1490)
Objective—To determine whether the angiotensin
converting enzyme inhibitor enalapril would lower
systemic arterial and glomerular capillary pressure
and reduce the magnitude of renal injury in a canine
model of renal insufficiency.
Animals—18 adult dogs that had renal mass reduced
by partial nephrectomy.
Procedure—After surgical reduction of renal mass
and baseline measurements, dogs in 2 equal groups
received either placebo (group 1) or enalapril (0.5
mg/kg, PO, q 12 h; group 2) for 6 months.
Results—Values for systemic mean arterial blood
pressure determined by indirect and direct measurement
after 3 and 6 months of treatment, respectively,
were significantly lower in group 2 than in group 1.
During treatment, monthly urine protein-to-creatinine
ratios were consistently lower in group 2 than in
group 1, although values were significantly different
only at 3 months. At 6 months, significant reduction
in glomerular capillary pressure in group 2 was detected,
compared with group 1, but glomerular filtration
rate in group 2 was not compromised. Glomerular
hypertrophy, assessed by measurement of planar surface
area of glomeruli, was similar in both groups.
Glomerular and tubulointerstitial lesions were significantly
less in group 2, compared with group 1.
Conclusions and Clinical Relevance—Data suggest
that inhibition of angiotensin converting enzyme was
effective in modulating progressive renal injury, which
was associated with reduction of glomerular and systemic
hypertension and proteinuria but not glomerular
hypertrophy. Inhibition of angiotensin converting
enzyme may be effective for modulating progression
of renal disease in dogs. (Am J Vet Res 2003;64:321–327)
Objective—To determine effects of an extract of
Serenoa repens on dogs with prostatic hyperplasia.
Animals—20 mature male dogs with benign prostatic
Procedure—Dogs were assigned to 3 comparable
groups on the basis of prostatic volume per kg of
body weight and degree of prostatic hyperplasia
determined histologically. Dogs in 2 groups were
treated for 91 days (8 received 500 mg, PO, q 8 h
[1,500 mg/d], and 6 received 100 mg, PO, q 8 h [300
mg/d]). The control group of 6 dogs did not receive
medication. Effects of treatment on prostatic volume,
prostatic weight, prostatic histologic characteristics,
radiographic and ultrasonographic assessment of prostatic
size, results of CBC, serum biochemical analyses,
and urinalysis, serum testosterone concentration,
and semen characteristics were determined. At
the termination of the study, all dogs were euthanatized,
and necropsies were performed. Investigators
conducting tests and interpreting results were not
aware of treatment group of each dog.
Results—Treatment did not affect prostatic weight,
prostatic volume, or prostatic histologic scores, libido,
semen characteristics, radiographs of the caudal portion
of the abdomen, prostatic ultrasonographs, or
serum testosterone concentrations. Results of CBC,
serum biochemical analyses or urinalysis, and body
weights did not change during treatment.
Conclusions and Clinical Relevance—Treatment with
an extract of S repens for 91 days did not significantly
affect the prostate gland of dogs. Adverse effects were
not evident. Although products containing extracts of S
repens are widely advertised for men with prostatic
hyperplasia, beneficial or harmful effects of this plant
extract were not found in dogs with prostatic hyperplasia.
(Am J Vet Res 2000;61:880–885)