Influence of alkali metal cations on the transport of calcium by phosphatidate in multi-phase systems.
The effects of alkali metal cations on the rates at which Ca2+ and phosphatidic acid were cotransported from aqueous to hydrocarbon medium were examined. The alkali metal cations remained in the aqueous phase yet specifically influenced the transport of Ca2+ into the hydrocarbon solvent. For the physiological cations, Na+ and K+, there were critical concentration ranges in which small changes in concentration effected sharp changes in transport rates. The maximal rate observed with Na+ was an order of magnitude greater than that with K+; however, unlike Na+, K+ promoted low levels of transport below the critical concentration range. Li+ effected only low levels of transport even at high concentrations, whereas Rb+ and Cs+ induced transport at rates proportional to their concentrations. These results are discussed in terms of a classical ionophore model for the complex composed of a neutral phosphatidic acid dimer bridged by Ca2+.
Reusch
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Dept. of Microbiology and Public Health, Michigan State University, E. Lansing 48824.
D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics*; D006863:Hydrogen-Ion Concentration; D007476:Ionophores; D008672:Metals, Alkali / Q000494:pharmacology*; D010712:Phosphatidic Acids / Q000737:chemistry / Q000378:metabolism*
D007476:Ionophores; D008672:Metals, Alkali; D010712:Phosphatidic Acids; D002118:Calcium