[Physico-chemical mechanisms of organic acid transport in the apical membrane cells of the proximal kidney tubules in rats. I. Kinetic transport parameters and effect of the lipid phasic state on transport].
The kinetics of the transport of 3H-para-aminohippuric acid (PAH) and the influence of the temperature on the initial rate of transport were studied on the vesicles of a purified fraction of the apical membrane isolated from cells of kidney proximal tubules. The PAH transport is accomplished owing to the facilitate diffusion mechanism. The apparent Michaelis constant at 36 degrees C was equal to 7.0 + 1.0 mM, the maximum rate was 15 nmol/min on 1 mg of protein, the inhibition constant for the PAH transport by probenecid being 0.5 mM. At 22 degrees C the apparent Michaelis constant was drastically increased. When the temperature dependence of the initial rate of PAH transport into vesicles was replotted in the form of the Arrhenius plot, there was a turning-point of the line at 28-30 degrees C. The same turning-point is shown on the Arrhenius plot for temperature dependence of alkaline phosphatase activity (a marker enzyme for the apical membrane). The electron paramagnetic resonance spectra analysis of 5-doxylstearate-labeled apical membrane preparation reveals a thermotropic transition near 21-29 degrees C. It is concluded that the function of the carrier and the activity of alkaline phosphatase depend on the phasic state of membrane lipids; the normal function of membrane proteins is possible under the liquid-crystalline state of the lipid bilayer.
Bresler
V M
VM
Val'ter
S N
SN
Isaev-Ivanov
V V
VV
Kazbekov
E N
EN
Kleĭner
A P
AP
D000618:Aminohippuric Acids / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002458:Cell Fractionation / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity; D051381:Rats; D013696:Temperature; D014316:Tritium; D010130:p-Aminohippuric Acid / Q000378:metabolism*
D000618:Aminohippuric Acids; D008051:Lipid Bilayers; D014316:Tritium; D010130:p-Aminohippuric Acid
Fiziko-khimicheskie mekhanizmy transporta organicheskikh kislot v vezikulakh apikal'noĭ membrany kletok proksimal'nykh kanal'tsev pochki krys. I. Kineticheskie parametry transporta i vliianie fazovogo sostoianiia na transport.