Effect of essential fatty acid deficiency on activity of liver plasma membrane enzymes in the rat.
Liver plasma membranes (LPM) were isolated from rats fed an essential fatty acid-supplemented diet (+EFA) or from rats fed an essential fatty acid-deficient diet (-EFA). The proportions of linoleate and arachidonate in membrane total fatty acids in the -EFA preparations were one-half or less than the values for the +EFA preparations. Basal, F-, or glucagon-stimulated adenylate cyclase activities were significantly lower in EFA-deficient livers than in nondeficient ones. Addition of GTP significantly enhanced glucagon-stimulated adrenylate cyclase in both groups, but extent of stimulation above basal was greater in EFA-deficient livers. Portal vein injection of glucagon in vivo resulted in significantly higher cAMP formation in +EFA livers than in -EFA livers. When glucagon was used in vitro at 1-1,000 nM, stimulation of adenylate cyclase remained lower in EFA-deficient membranes, but extent of stimulation above basal activity was larger in -EFA membranes than in +EFA. Total Na+, K+ (Mg2+)-ATPase from EFA-depleted LPM exhibited significantly higher values of apparent Km and Vmax-5'-Nucleotidase activity, in contrast, was considerably decreased in EFA-deficient rats. These findings show that, in animals, changes in unsaturated fatty acid composition can affect the properties of membrane-bound enzymes. These alterations could be due to changes in membrane physical properties and/or prostaglandin formation.
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D003579:Cytochrome Reductases / Q000378:metabolism; D005228:Fatty Acids, Essential / Q000172:deficiency / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology; D005952:Glucose-6-Phosphatase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D009708:Nucleotidases / Q000378:metabolism; D051381:Rats
D005228:Fatty Acids, Essential; D005934:Glucagon; D003579:Cytochrome Reductases; D009708:Nucleotidases; D000469:Alkaline Phosphatase; D005952:Glucose-6-Phosphatase; D000251:Adenosine Triphosphatases; D000262:Adenylyl Cyclases