Graduate Thesis Or Dissertation

 

Active uptake of chloride across the skin of the frog, Rana pipiens (Schreber) Público Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/gh93h2723

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  • Chloride is actively transported across the skin of the intact leopard frog, Rana pipiens. The influx and efflux in 0.2 mM NaC1 are 0.67 and 0. 72 μeq/10 g-hr, respectively. The renal efflux of chloride is 0.02 μeq/10 g-h . The transepithelial potential differences (TEP) range from -1 to +32 mV (sign refers to the inside). The mean measured ratio of influx to efflux is 0.93. The flux ratio predicted from the flux ratio equation is 0.005. Clearly, chloride is actively transported. With 0.2 mM KC1 in the external bath, the influx and efflux of chloride (0.57 and 1.05 μeq/10 g-hr, respectively) are not significantly different from the values obtained in 0.2 mM NaC1. The measured and predicted flux ratios are 0.54 and 0.002, respectively. Chloride is actively transported, and this transport is not dependent on the movement of sodium. The TEP is independent of the concentration of anion (chloride or sulfate) in the external bath. With increasing sodium concentration (NaC1 or Na₂SO₄) in the external medium, the body fluids become more electropositive relative to the bath (the slope of the line is 22 mV /log[mM]). At high sodium concentrations (50 mM), the magnitude of the TEP is reduced with increasing bath concentration probably as a result of increased permeability of the skin to chloride. The TEP is independent of the K⁺ concentration in the external medium. The influx of chloride increases with increasing chloride concentration in the external bath at lower concentrations. The transporting system shows Michaelis-type kinetics. For NaC1, V[subscript]max = 1.3 μeq/10 g-hr and K[subscript]m = 0.18 mM. For KC1, V[subscript]max = 1.2 μeq/10 g-hr and K[subscript]m = 0.38 mM. Salt-depleted animals absorb net amounts of chloride (0.78 μeq/ 10 g-hr) from 1.0 mM KC1 and lose net amounts of sodium and potassium (1.10 and 0.58 μeq/10 g-hr, respectively). When animals "pump" chloride from 1.0 mM KC1, the bath becomes more alkaline. The pH increases at the rate of 0.056 pH units/hr. The animals excrete net quantities of base (3.23 μeq/10 g-hr). The pK[subscript]b of the base excreted is 6.0. The pK[subscripted]b of KHCO₃ in KC1 is 6.1. The excreted base is probably bicarbonate ion which exchanges for the absorbed chloride.
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