Comparison between (RS)-nipecotic acid and GABA transport in cultured astrocytes: coupling with two sodium ions.
The sodium ion dependency of the uptake of (RS)-nipecotic acid into astrocytes in primary cultures has been studied by performing kinetic analysis at different sodium ion concentrations (16--151 mM). Vmax of the saturable component of the astroglial (RS)-nipecotic acid uptake is clearly affected by the sodium ion concentration whereas Km surprisingly remains unaffected. At high (RS)-nipecotic acid concentrations (Greater Than or Equal To 50 mu M), uptake rates as a function of the sodium ion concentration were clearly sigmoid. This sigmoid shape was not obvious at lower concentrations of (RS)-nipecotic acid. The calculated Hill coefficients corresponding to all (RS)-nipecotic acid concentrations studied were approximately two. From these results it is concluded that (RS)-nipecotic acid uptake into astrocytes in primary cultures, like astroglial GABA uptake, requires the binding of at least two sodium ions per (RS)-nipecotic acid molecule transported.
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D007700:Kinetics; D051379:Mice; D009557:Nipecotic Acids / Q000378:metabolism*; D011392:Proline / Q000031:analogs & derivatives*; D012964:Sodium / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D009557:Nipecotic Acids; C030278:nipecotic acid; D005680:gamma-Aminobutyric Acid; D011392:Proline; D012964:Sodium; C010983:homoproline