Sodium balance in the newt, Notophthalmus viridescens

1. 1. Sodium fluxes in Notophthalmus viridescens were found to be higher than those of any amphibian examined to date. 2. 2. The total sodium loss from unfed animals was 49.4 μ-equiv/g/day, or ca . 102% of total body sodium/day. 3. 3. Integumental loss accounted for 68% of the total; urinary loss, 32%. 4. 4. Integumental sodium uptake exhibited saturation kinetics, with a J max = 234 μ-equiv/g/day and a k m = 2.1 m-equiv/l. 5. 5. The high capacity of the transport system allows losses to be replaced at external sodium concentrations approaching 0.1 m-equiv/l.