Oleic acid inhibition of Na+/D-glucose transport in isolated renal brush-border membranes: role of lipid physical parameters and trans Na(+)-inhibition.
Inhibition of Na+/D-glucose transport by oleic acid was investigated in renal brush-border membrane vesicles (BBMV). Lipid physical parameters were determined by spectrofluorometry. cis-Unsaturated C16-C22 long-chain fatty acids (LCFA) as oleic acid reduced nonzero limiting anisotropy r infinity with DPH and 12-AS as probes and decreased rotational correlation time phi of 12-AS. At 8 s and 15 s Na+/D-glucose transport was competitively inhibited. A positive correlation existed between decrease in r infinity (acyl chain order) or decrease in rotational correlation time phi (= increase in 'fluidity') and inhibition of Na+/D-glucose transport. Except elaidic acid trans unsaturated and saturated LCFA had no effect on fluorescence anisotropy and Na+/D-glucose transport. Per cent transport inhibition was unaffected by 0 voltage clamping and by FCCP. Ki for trans Na(+)-inhibition of D-glucose transport was 29 mmol/l. Na(+)-transport was stimulated by oleic acid, exceeding the Ki value for trans Na+ inhibition.


CONCLUSIONS
oleic acid inhibits Na+/D-glucose transport by a decrease in lipid acyl chain order and an increase in 'fluidity', by trans Na(+)-inhibition and presumably by a third unknown mechanism.
Wagner
S
S
Institut für Klinische Physiologie, Klinikum Steglitz, Freie Universität Berlin, Germany.
Wenzel-Seifert
K
K
Volbracht
L
L
Sorgenfrei
D
D
Ebel
H
H
D000818:Animals; D001692:Biological Transport; D005454:Fluorescence Polarization; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D008297:Male; D008560:Membrane Fluidity; D008871:Microvilli / Q000187:drug effects; D009004:Monosaccharide Transport Proteins / Q000037:antagonists & inhibitors*; D019301:Oleic Acid; D009829:Oleic Acids / Q000737:chemistry / Q000494:pharmacology*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
D009004:Monosaccharide Transport Proteins; D009829:Oleic Acids; D010169:Palmitic Acids; D019301:Oleic Acid; D019308:Palmitic Acid; D012964:Sodium; D011188:Potassium