Effect of lipopolysaccharide on nitric oxide synthase activity in rat proximal tubules.
Renal proximal tubules isolated from the rat possess nitric oxide synthase (NOS) activity that is calcium/calmodulin dependent and stereoselectively inhibited by NG-monomethyl-arginine (NMMA). In the absence of added Ca2+ and calmodulin, activity was reduced 84 +/- 13% compared with the activity in the presence of 2 mM Ca2+ and 25 micrograms/mL calmodulin. Inhibition by EGTA (10 mM) was 95 +/- 5% and by calmidazolium (R24571, 250 microM) was 99 +/- 1%. Inhibition by L-NMMA (100 microM) was 78 +/- 13% and by D-NMMA (100 microM) was 7 +/- 7%. The majority of NOS activity was found in the soluble fraction. NOS activity in isolated proximal tubules was also examined 6 hr after a single i.v. injection of lipopolysaccharide. Activity was increased significantly (P < 0.05) in the soluble fraction by 2-fold [from 0.320 +/- 0.052 to 0.648 +/- 0.046 (nmol/mg protein/30 min)] and in the particulate fraction by 3-fold [from 0.081 +/- 0.030 to 0.256 +/- 0.034 (nmol/mg protein/30 min)]. All activities were inhibited by EGTA. These data demonstrate that proximal tubules express a calcium/calmodulin-dependent NOS activity that is increased in vivo by lipopolysaccharide.
Mayeux
P R
PR
Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205.
Garner
H R
HR
Gibson
J D
JD
Beanum
V C
VC
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D002956:Citrulline / Q000032:analysis / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D009249:NADP / Q000378:metabolism; D019001:Nitric Oxide Synthase; D051381:Rats; D017207:Rats, Sprague-Dawley; D019323:omega-N-Methylarginine
D008070:Lipopolysaccharides; D019323:omega-N-Methylarginine; D002956:Citrulline; D009249:NADP; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases