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Phosphate uptake across amphibian skin is active and sodium dependent
Author(s) -
Møbjerg Nadja
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a510-c
Subject(s) - phosphate , sodium , chemistry , efflux , amphibian , frog skin , biophysics , transepithelial potential difference , mannitol , biochemistry , ion transporter , biology , membrane , ecology , organic chemistry
We have recently cloned a NaPi‐IIb transporter (SLC34A2), which is expressed in skin, small intestine and kidney of toads ( Bufo bufo ) [1]. Furthermore, we have shown that toads take up inorganic phosphate (P i ) across the skin. The aim of this study was to characterize cutaneous P i absorption. Unidirectional 32 P‐labelled phosphate fluxes were measured across isolated preparations mounted in an Ussing chamber. In sets of paired, short‐circuited skin exposed to identical Ringer solutions on both sides, influx exceeded efflux with a flux ratio varying from 2.3 to 15.3 with mean±sd of 7.5±5.6 (n=7). This would indicate that phosphate uptake is active. Experiments with increasing external sodium concentration demonstrated sodium dependent phosphate uptake by a saturable transport system with an apparent affinity constant for sodium of 11±1.4 mM (n=3). Phosphate influx to efflux ratio was not depressed by amiloride and concomitant experiments with unidirectional mannitol fluxes indicated that solvent drag can not account for net phosphate uptake. These results support the hypothesis that phosphate uptake across amphibian skin is active and possibly mediated by NaPi‐IIb. Supported by Danish Natural Science Research Council.