First published online August 8, 2003
Urea transport in kidney brush-border membrane vesicles from an elasmobranch, Raja erinacea
Robyn L. Morgan,
Patricia A. Wright* and
James S. Ballantyne
Department of Zoology, University of Guelph, Guelph, Ontario, Canada,
N1G 2W1
View larger version (15K):
[in a new window]
|
Fig. 1. (A) Rates of urea uptake at various urea concentrations in dorsal BBMV from
the kidney of the little skate Raja erinacea. The regression is
y=0.3309x, r2=0.9708. Values are means ±
S.E.M., N=5. (B) Expansion of the lower end of the urea
concentration range, subtracting the linear rate from A. The regression is
y=0.563x, r2=0.8413. Values are means ±
S.E.M., N=6.
|
|
View larger version (18K):
[in a new window]
|
Fig. 2. (A) Rates of urea uptake at various urea concentrations in ventral BBMV
from the kidney of the little skate Raja erinacea. The regression is
y=0.3312x, r2=0.9724. Values are means ±
S.E.M., N=5. (B) Expansion of the lower end of the urea
concentration range, subtracting the linear rate from A. The regression is
y=1.3941x/(0.9016+x),
r2=0.9561. Values are means ± S.E.M.,
N=6. (C) Lineweaver–Burk transformation of the relationship
between urea concentration and urea uptake V (µmol
h–1 mg–1 protein) by BBMV. The regression is
y=0.5988x+0.8308, r2=0.9330. Values are
means ± S.E.M., N=6.
|
|
View larger version (15K):
[in a new window]
|
Fig. 3. Inhibition of urea uptake by phloretin (0.50 mmol l–1),
mercury chloride (HgCl2; 0.30 mmol l–1) and
phloretin (0.50 mmol l–1) + HgCl2 (0.30 mmol
l–1) in dorsal and ventral BBMV from the kidney of the little
skate Raja erinacea. Urea concentration in the incubation medium was
0.5 mmol l–1. Control urea uptake rates are 1.42±0.14
and 1.41±0.18 µmol h–1 mg–1
protein, for dorsal and ventral sections, respectively. Values are means
± S.E.M., N=5–7. *Significant
difference from respective control;  significant difference
from dorsal phloretin (ANOVA on log-transformed data, Tukey–Kramer
multiple comparison test, P<0.05).
|
|
View larger version (16K):
[in a new window]
|
Fig. 4. Effect on urea uptake in the dorsal and ventral BBMV from the kidney of the
little skate Raja erinacea, by the urea analogs acetamide,
N-methylurea (370 mmol l–1) and nitrophenylthiourea
(NPTU; 0.08 mmol l–1). Urea concentration in the incubation
medium was 0.5 mmol l–1. Control rates are 1.32±0.19
and 0.97±0.09 µmol h–1 mg–1
protein, for dorsal and ventral sections, respectively. Values are means
± S.E.M., N=5. *Significant difference
from dorsal control (ANOVA on log-transformed data, Tukey–Kramer
multiple comparison test, P<0.05); significant
difference from dorsal acetamide (Student t-test on log-transformed
data, P<0.05).
|
|
View larger version (15K):
[in a new window]
|
Fig. 5. The effect of Na+ and K+ on the rate of urea
transport in the dorsal and ventral BBMV from the kidney of the little skate
Raja erinacea, presented as percentage of control (no ion gradient).
Urea concentration in the incubation medium was 4 mmol l–1.
Control rates are 1.53±0.32 and 1.56±0.29 µmol
h–1 mg–1 protein, for the dorsal section
Na+ and K+, respectively, and 1.77±0.44 and
1.42±0.35 µmol h–1 mg–1 protein,
for the ventral section Na+ and K+ respectively. Values
are means ± S.E.M., N=4. *Significant
difference from ventral sodium control (Student t-test,
P<0.05).
|
|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
© The Company of Biologists Ltd 2003
