The effect of prior exposure on sodium uptake in tadpoles exposed to low pH water |
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Authors: | Joseph Freda William A Dunson |
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Institution: | (1) Department of Biology, The Pennsylvania State University, 16802 University Park, Pennsylvania, USA;(2) Present address: Department of Biology, McMaster University, L8S 4K1 Hamilton, Ontario, Canada |
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Abstract: | Summary Bullfrog tadpoles (Rana catesbeiana) were pre-exposed (7d) to 5 different solutions which varied in ionic composition and pH. Unidirectional sodium influx was then measured over a range of sodium concentrations (50–2000 M) and at 2 pH's (4.0 and 5.8). Tadpoles pre-treated in either distilled water or pH 4.0 soft water exhibited higher sodium influx than animals pre-treated in pH 5.8 soft water. Pre-exposure to solutions high in calcium or sodium reduced sodium influx. Tadpoles pre-treated in pH 4.0 soft water exhibited an increasedV
max for sodium transport, whileK
m was unchanged relative to tadpoles pre-treated in pH 5.8 soft water. In contrast,K
m was increased andV
max was unchanged in tadpoles pre-exposed to high concentrations of calcium or sodium. Within each pre-exposure treatment, influx was inhibited in pH 4.0 test water relative to pH 5.8 test water. However, the magnitude of inhibition was lessened with increasing external concentrations of sodium.Abbreviations
ASW
artificial soft water
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DBM
dry body mass
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DW
distilled water |
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Keywords: | |
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