Biomaterial Database

Active transport of iodide and other anions across the choroid plexus. 1974

E M Wright

1. An in vitro preparation of the frog choroid plexus was used to study mechanisms of anion transport.2. It was observed that, in the absence of electrochemical potential gradients, there were net fluxes of I(-), SCN(-), TcO(4) (-), and Br(-) across the plexus, from the ventricular to the serosal surface. The net flux of I(-) reached a maximum at a concentration of 250 muM.3. On the basis of competition effects it was concluded that the affinity of the transport process for anions was: ClO(4) > ReO(4) approximately BF(4) > SCN approximately SeCN > I > NO(3) > Br > Cl.4. Ouabain, oligomycin, phloretin and 2,4-DNP inhibited the net transport of anions, but phlorrhizin, furosemide, 2,4,6-trinitro-m-cresolate, reducing agents, and antithyroid agents did not. Ouabain and phloretin were only effective on the ventricular side of the preparation.5. Anion transport required the presence of both Na and K. The requirement for Na was specific, but Rb, and to a lesser extent Cs, could substitute for K. Na in either the ventricular or the serosal fluids could partially stimulate anion transport, but K was only effective in the ventricular solution.6. TcO(4) (-), SCN(-) and I(-) were accumulated within the choroidal epithelium from the ventricular fluid, but not from the serosal fluid. Accumulation was inhibited by ouabain and ClO(4) (-).7. The unidirectional influx of I(-) across the apical cell membrane was about an order of magnitude greater than the flux across the epithelium. This flux was inhibited by ClO(4) (-), ouabain, and Na-free solutions.8. These experiments suggest the following mechanism for anion transport across the plexus: anions are actively transported into the epithelium, by a ouabain sensitive, Na/K dependent pump located in the brush border membrane. The anions are accumulated within the epithelium, and, finally, they pass into the serosal fluid down their electrochemical potential gradient. Relations between anion transport, Na/K transport, and Na/K ATPases are discussed.

UI	MeSH Term	Description	Entries
D007454	Iodides	Inorganic binary compounds of iodine or the I- ion.	Iodide
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008297	Male		Males
D009566	Nitrates	Inorganic or organic salts and esters of nitric acid. These compounds contain the NO3- radical.	Nitrate
D009840	Oligomycins	A closely related group of toxic substances elaborated by various strains of Streptomyces. They are 26-membered macrolides with lactone moieties and double bonds and inhibit various ATPases, causing uncoupling of phosphorylation from mitochondrial respiration. Used as tools in cytochemistry. Some specific oligomycins are RUTAMYCIN, peliomycin, and botrycidin (formerly venturicidin X).	Oligomycin
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
D010472	Perchlorates	Compounds that contain the Cl(	Perchloric Acid Derivatives,Perchloric Acids,Acids, Perchloric
D010693	Phloretin	A natural dihydrochalcone found in apples and many other fruits.
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D011892	Rana catesbeiana	A species of the family Ranidae (true frogs). The only anuran properly referred to by the common name "bullfrog", it is the largest native anuran in North America.	Bullfrog,Bullfrogs,Rana catesbeianas,catesbeiana, Rana