Changes In Ion Fluxes Research Articles

The effects of carbon dioxide and hydrogen ion on sodium transport in isolated frog skin

A detailed study has been made of the effect of CO 2 and hydrogen ion on the sodium ion transport system of isolated frog skin. The short-circuit technique has been used as a measure of the net sodium flux, and open circuit potential measurements were made as well. The sodium ion flux was investigated as a function of sodium ion concentration in the solution bathing the external surface at a variety of pH's in the range 6–8. 4. These data were subject to analysis in terms of a model previously proposed and the inhibition of the sodium transport system by H + was found to be interpretable as non-competititve. The sodium ion flux was also investigated following step changes in pH of the bathing solutions as well as changes in buffer system at the same pH. The resulting transient changes in sodium ion flux are interpreted with the aid of a simple model mechanism which accounts for the observed differences in effect between a CO 2HCO 3 buffer and phosphate buffer in terms of the relative rapid diffusion of CO 2 leading to local changes in H + concentration at the site of the transport system.

The effect of ultraviolet light on the sodium and potassium composition of resting yeast cells.

The Na(+) and K(+) content of non-metabolizing yeast cells was determined before and after monochromatic ultraviolet (UV) irradiation. UV facilitated the uptake of Na(+) into and the loss of K(+) from the cells (net ion flux); the effect is greatest for the shortest wavelength employed (239 mmicro) and is partly dependent upon the presence of oxygen. The UV effect on net ion flux persists for at least 90 minutes during which tests were made and it occurs following dosages which are without measurable effect on colony formation. The UV effect on net ion flux is decreased by acidity and promoted by alkalinity. Addition of calcium ions in sufficient amount prevents the usual net ion flux changes observed in irradiated yeast. Increase in concentration gradient between the inside and the outside of the cell increases the net ion flux of irradiated yeast, Na(+) uptake leading K(+) loss in all cases. UV appears to act by disorganizing the constituents of the cell surface, permitting K(+) to leave the cell in exchange for Na(+). At low intensities of UV this ionic exchange approaches equivalence, but at higher intensities more Na(+) is taken up than K(+) is lost. Some evidence suggests that the Na(+) in excess over that exchanged for K(+) is adsorbed to charged groups produced by the photochemical effect of UV on the cell surface.

Case of Rhinolith: With Remarks

Ion flux kinetics associated with blue light (BL) treatment of two wild types (WTs) and the phot1, phot2 and phot1/phot2 mutants of Arabidopsis were studied by using the MIFE noninvasive ion-selective microelectrode technique. BL induced significant changes in activity of H+ and Ca2+ transporters within the first 10 min of BL onset, peaking between 3 and 5 min. In all WT plants and in phot2 mutants, BL induced immediate Ca2+ influx. In phot1 and phot1/phot2 mutants, net Ca2+ flux remained steady. It is suggested that PHOT1 regulates Ca2+ uptake into the cytoplasm from the apoplast. Changes in ion fluxes were measured from cotyledons of intact seedlings and from the cut top of the hypocotyl of decapitated seedlings. Thus the photoreceptors mediating BL-induced Ca2+ and H+ fluxes are present in the rest of the decapitated seedling and probably in the cotyledons as well. The H+ and Ca2+ flux responses to BL appear not to be linked because, (i) when changes were observed for both ions, Ca2+ flux changed almost immediately, whereas H+ flux lagged by about 1.5 min; (ii) in the Wassilewskija ecotype, changes in H+ fluxes were small. Finally, wave-like changes in Ca2+ and H+ concentrations were observed along the cotyledon–hook axis regardless of its orientation to the light.