Journal Title
Title of Journal: J Comp Physiol B
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Abbravation: Journal of Comparative Physiology B
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Publisher
Springer-Verlag
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Authors: M D McDonald C M Wood M Grosell P J Walsh
Publish Date: 2004/10/28
Volume: 174, Issue: 8, Pages: 649-658
Abstract
The objectives of this study were to characterize the pattern of pulsatile urea excretion in the gulf toadfish in the wake of exogenous cortisol loading and to determine the receptors involved in the regulation of this mechanism Toadfish were fitted with indwelling arterial catheters and were infused with isosmotic NaCl for 48 h after which fish were treated with cortisol alone cortisol+peanut oil cortisol+RU486 a glucocorticoid receptor antagonist or cortisol+spironolactone a mineralocorticoid receptor antagonist Upon cortisol loading fish treated with cortisol alone cortisol+oil or cortisol+spironolactone experienced a two to threefold reduction in pulsatile urea excretion This reduction was due to a decrease in urea pulse size with no effect on pulse frequency compared to values measured during the control NaCl infusion period In addition these fish showed an increase in plasma urea concentrations upon treatment These apparent effects of cortisol treatment were abolished in fish treated with cortisol+RU486 In contrast these fish showed an increase in pulsatile urea excretion mediated by a twofold increase in pulse size with no change in frequency Likewise fish treated with cortisol+RU486 showed a significant decrease in plasma urea concentrations over the course of the experiment The findings of this study indicate that high levels of cortisol reduce pulsatile urea excretion by decreasing pulse size In addition it appears that glucocorticoid receptors and not mineralocorticoid receptors are involved in the regulation of the toadfish pulsatile urea excretion mechanismThis study was supported by an OGS CANADA scholarship awarded to MDM an NSERC CANADA basic discovery grant awarded to CMW an NSF USA research grant IBN0090355 to PJW and an NIEH Marine and Freshwater Biomedical Sciences Center Grant ES 05705 to the University of Miami Sincere thanks to Jimbo Luznar and his boat captains for their supply of toadfish CMW is supported by the Canada Research Chair program
Keywords:
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