Abstract
The objective of this study was to determine whether the pulsatile facilitated diffusion transport mechanism (tUT) found in the gills of the gulf toadfish (Opsanus beta) and the active secretion transporter thought to be present in its kidney could be saturated when faced with elevated plasma urea concentrations. Toadfish were infused with four consecutive exogenous urea loads at a rate of 0, 150, 300 and 600 μmol kg-1 h-1. Initial plasma and urine urea concentrations were 8.1±0.9 and 12.4±1.5 mmol l-1, respectively, and steadily increased with increasing infused loads of urea to a maximum of 36.8±2.8 mmol l-1 in the plasma and 39.8±6.5 mmol l-1 in the urine. There was only a very weak relationship (r=0.17) between pulse size (measured as branchial excretion during pulsatile excretion of urea) and plasma urea concentration (slope=9.79 μmol-N kg-1 per mmol-N l-1; P<0.05) suggesting that the branchial excretion mechanism was already saturated at normal plasma urea concentrations. Urine flow rate (0.15±0.03 ml kg-1 h-1) and glomerular filtration rate (0.025±0.004 ml kg-1 h-1) remained constant throughout the experiment despite the increased volume load. Renal urea secretion rate maintained a strong linear relationship (r=0.84) to plasma urea levels (slope=0.391 μmol-N kg-1 h-1 per mmol-N l-1; P<0.001) with no observable transport maximum, suggesting that the renal secretory transport mechanism was not saturated even at plasma urea levels well above normal, in contrast to the branchial excretion mechanism.
| Original language | English |
|---|---|
| Pages (from-to) | 763-776 |
| Number of pages | 14 |
| Journal | Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology |
| Volume | 134 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 1 2003 |
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Keywords
- Gills
- Gulf toadfish
- Kidney, Opsanus beta
- Transport kinetics
- Urea
- Urea infusion
- Urea transport protein (tUT)
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Physiology
Cite this
Branchial and renal handling of urea in the gulf toadfish, Opsanus beta : The effect of exogenous urea loading. / Mcdonald, Danielle M; Grosell, Martin; Wood, Chris M.; Walsh, Patrick J.
In: Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology, Vol. 134, No. 4, 01.04.2003, p. 763-776.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Branchial and renal handling of urea in the gulf toadfish, Opsanus beta
T2 - The effect of exogenous urea loading
AU - Mcdonald, Danielle M
AU - Grosell, Martin
AU - Wood, Chris M.
AU - Walsh, Patrick J.
PY - 2003/4/1
Y1 - 2003/4/1
N2 - The objective of this study was to determine whether the pulsatile facilitated diffusion transport mechanism (tUT) found in the gills of the gulf toadfish (Opsanus beta) and the active secretion transporter thought to be present in its kidney could be saturated when faced with elevated plasma urea concentrations. Toadfish were infused with four consecutive exogenous urea loads at a rate of 0, 150, 300 and 600 μmol kg-1 h-1. Initial plasma and urine urea concentrations were 8.1±0.9 and 12.4±1.5 mmol l-1, respectively, and steadily increased with increasing infused loads of urea to a maximum of 36.8±2.8 mmol l-1 in the plasma and 39.8±6.5 mmol l-1 in the urine. There was only a very weak relationship (r=0.17) between pulse size (measured as branchial excretion during pulsatile excretion of urea) and plasma urea concentration (slope=9.79 μmol-N kg-1 per mmol-N l-1; P<0.05) suggesting that the branchial excretion mechanism was already saturated at normal plasma urea concentrations. Urine flow rate (0.15±0.03 ml kg-1 h-1) and glomerular filtration rate (0.025±0.004 ml kg-1 h-1) remained constant throughout the experiment despite the increased volume load. Renal urea secretion rate maintained a strong linear relationship (r=0.84) to plasma urea levels (slope=0.391 μmol-N kg-1 h-1 per mmol-N l-1; P<0.001) with no observable transport maximum, suggesting that the renal secretory transport mechanism was not saturated even at plasma urea levels well above normal, in contrast to the branchial excretion mechanism.
AB - The objective of this study was to determine whether the pulsatile facilitated diffusion transport mechanism (tUT) found in the gills of the gulf toadfish (Opsanus beta) and the active secretion transporter thought to be present in its kidney could be saturated when faced with elevated plasma urea concentrations. Toadfish were infused with four consecutive exogenous urea loads at a rate of 0, 150, 300 and 600 μmol kg-1 h-1. Initial plasma and urine urea concentrations were 8.1±0.9 and 12.4±1.5 mmol l-1, respectively, and steadily increased with increasing infused loads of urea to a maximum of 36.8±2.8 mmol l-1 in the plasma and 39.8±6.5 mmol l-1 in the urine. There was only a very weak relationship (r=0.17) between pulse size (measured as branchial excretion during pulsatile excretion of urea) and plasma urea concentration (slope=9.79 μmol-N kg-1 per mmol-N l-1; P<0.05) suggesting that the branchial excretion mechanism was already saturated at normal plasma urea concentrations. Urine flow rate (0.15±0.03 ml kg-1 h-1) and glomerular filtration rate (0.025±0.004 ml kg-1 h-1) remained constant throughout the experiment despite the increased volume load. Renal urea secretion rate maintained a strong linear relationship (r=0.84) to plasma urea levels (slope=0.391 μmol-N kg-1 h-1 per mmol-N l-1; P<0.001) with no observable transport maximum, suggesting that the renal secretory transport mechanism was not saturated even at plasma urea levels well above normal, in contrast to the branchial excretion mechanism.
KW - Gills
KW - Gulf toadfish
KW - Kidney, Opsanus beta
KW - Transport kinetics
KW - Urea
KW - Urea infusion
KW - Urea transport protein (tUT)
UR - http://www.scopus.com/inward/record.url?scp=0037603386&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037603386&partnerID=8YFLogxK
U2 - 10.1016/S1095-6433(03)00010-2
DO - 10.1016/S1095-6433(03)00010-2
M3 - Article
VL - 134
SP - 763
EP - 776
JO - Comparative Biochemistry & Physiology; A: Comparative Physiology
JF - Comparative Biochemistry & Physiology; A: Comparative Physiology
SN - 1095-6433
IS - 4
ER -