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First published online August 8, 2003

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Regulation of a renal urea transporter with reduced salinity in a marine elasmobranch, Raja erinacea

Robyn L. Morgan, James S. Ballantyne and Patricia A. Wright^*

Department of Zoology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1

View larger version (19K): [in a new window]   Fig. 1. Simplified drawing of the skate kidney nephron, confined within the peritubular sheath in the dorsal zone (dorsal–lateral bundle) and unconfined in the ventral zones in blood sinuses. Arrows indicate direction of tubular flow from the renal corpuscle (RC) to the collecting duct. Roman numerals indicate loop number. (After Lacy et al., 1985.)

View larger version (16K): [in a new window]   Fig. 2. Urea concentrations in the dorsal and ventral regions of the kidney of the little skate Raja erinacea exposed to 100% and 50% seawater for 5 days. Values are means ± S.E.M., N=5. Values sharing the same letter are not significantly different (Tukey test, P<0.05).

View larger version (14K): [in a new window]   Fig. 3. Trimethylamine oxide (TMAO) concentrations in the dorsal and ventral regions of the kidney of the little skate Raja erinacea exposed to 100% and 50% seawater for 5 days. Values are means ± S.E.M., N=5.

View larger version (96K): [in a new window]   Fig. 4. Alignment of SkUT with other urea transporter (UT) proteins. Abbreviations and accession numbers are as follows: ShUT, shark UT, AF257331; mtUT, Magadi tilapia UT, AF278537; tUT, toadfish UT, AF165893; eUT, eel UT, AB049726; rUT-A2, rat UT-A2, U09957; rUT-B, rat UT-B, X98399. Black boxes denote identical amino acid residues, grey boxes denote conservative substitutions, and clear areas denote non-identity. *Indicates possible N-glycosylation site; underline indicates conserved amino acid motif.

View larger version (114K): [in a new window]   Fig. 5. Tissue distribution of SkUT using high-stringency northern analysis. Membranes were probed using 32P-labelled random-primed SkUT cDNA probe and hybridized at 65°C. Each lane contained 10 µg of total RNA. K, kidney; L, liver; G, gill; B, brain; H, heart; I, intestine; M, muscle. The positions of kb markers are shown.

View larger version (14K): [in a new window]   Fig. 6. Expression of SkUT mRNA relative to ß-actin mRNA in the dorsal and ventral regions of the kidney of the little skate, Raja erinacea, exposed to 50% seawater for 5 days. The signal of each band was measured by densitometry and presented as a ratio (SkUT/ß-actin) (see Materials and methods). Values are means ± S.E.M., N=4. *Significant difference to respective control (Student's t-test, P<0.05).