Electrogenic sodium pump

Figure 2. Sodium and chloride uptake across an idealised freshwater-adapted gill epithelium (chloride cell), which has the typical characteristics of ion-transporting epithelia in eukaryotes. In the example, the abundance of fixed negative charges (muco-proteins) in the unstirred layer may generate a Donnan potential (mucus positive with respect to the water) which is a major part of the net transepithelial potential (serosal positive with respect to water). Mucus also contains carbonic anhydrase (CA) which facilitates dissipation of the [H+] and [HCO(] to CO2, thus maintaining the concentration gradients for these counter ions which partly contribute to Na+ import (secondary transport), whilst the main driving force is derived from the electrogenic sodium pump (see the text for details). Large arrow indicates water flow...

B2 albuterol Butoxamine Inhibitory may involve t in electrogenic sodium pump t cAMP... 

Gibb, L.E. Eddy, A.A. (1972). An electrogenic sodium pump as a possible factor leading to the concentration of amino acids by mouse ascites-tumour cells with reversed sodium ion concentration gradients. Biochem. J. 129, 979-981. 

Johnson SW, Seutin V, North RA (1992) Burst firing in dopamine neurons induced by N-methyl-D-aspartate role of electrogenic sodium pump. Science 255 665-667. 

Kehoe, J.S., and P. Ascher. 1970. Re-evaluation of the synaptic activation of an electrogenic sodium pump. Nature 225 280. 

Pinsker, H., and E.R. Kandel. 1969. Synaptic activation of an electrogenic sodium pump. Science 163 931. 

ATP hydrolysis occurs on the cytoplasmic side of the membrane (Figure 10.8), and the net movement of one positive charge outward per cycle makes the sodium pump electrogenic in nature. 

Figure 9.29 Some mammalian (left) and microbial (right) membrane transport systems. (A) Primary electrogenic mechanisms (pumps) creating either a Na+ or a H+ gradient. (B) Secondary active transport systems of the symport type, in which the entry of a nutrient S into the cell is coupled with the entry of either the sodium ions or protons. (D) Various passive ion movements, possibly via channels or uniports. (Reproduced by permission from Serrano R. Plasma Membrane ATPase of Plants and Fungi. Boca Raton CRC Press, 1985, p. 59.)...

Fig. 3 shows a single sodium pump in the peritubular cell membrane since the Na extrusion mechanism is not necessarily linked with K uptake into the cell. The intracellular [K ] can all be accounted for on the basis of a passive electro-chemical equilibrium distribution of potassium. The peritubular membrane is known (Giebisch, 1961) to be highly permeable to K" ion and to exhibit a high K selectivity. The observation that the peritubular membrane of the Necturus proximal tubule is characterized by = E may be explained in one of two ways. Either that the PD across the peritubular cell membrane is mainly due to a K" " diffusion potential, or that the peritubular cationic pump is an electrogenic Na pump which by its operation generates E. Then a passive influx occurs to the point where Ej = E. ... 

Among the other possible cellular receptors tested, it was found that palytoxin caused K " efflux in yeast expressing a hybrid between the Na KVATPase and the H, K -ATPase, converting this enzyme into and open channel. Interestingly, subsequent studies have described palytoxin-stimu-lated cation fluxes that were blocked by vanadate but resistant to ouabain in rat colon, suggesting that the toxin was able to convert a vanadate-sensitive H K ATPase into an electrogenic cation transporter and consequently, that the pore-forming action of palytoxin was not restricted to Na, K -ATPase since it was also observed with the coloific H, KVATPase, which is related to the sodium pmnp. The toxin was also found to interfere with the sarcolemmal calcium pump in cardiac myocytes as a secondary effect. Further smdies are required to determine how palytoxin interferes with each of the P-type ATPase pmnps or if the effects of the toxin on these pumps are consequences of structural similarities between the enzymes. ... 

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