Lack of iNOS induction in a severe model of transient focal cerebral ischemia in rats.
Calcium-independent nitric oxide synthase (NOS) activity has been reported in ischemic brains and usually attributed to the inducible isoform, iNOS. Because calcium-independent mechanisms have recently been shown to regulate the constitutive calcium-dependent NOS, we proposed to confirm the presence of iNOS activity in our model of transient focal cerebral ischemia in rats. Our initial results showed that, in our model, ischemia induced an important increase in brain calcium concentration. Consequently, the determination of calcium-independent NOS activity required a higher concentration of calcium chelator than classically used in the NOS assay. In these conditions, calcium-independent NOS activity was not observed after ischemia. Moreover, our ischemia was associated with neither iNOS protein expression, measured by Western blotting, nor increased NO production, evaluated by its metabolites (nitrate/nitrite). Our results demonstrate that iNOS activity may be overestimated due to increased brain calcium concentration in ischemic conditions and also that iNOS is not systematically induced after cerebral ischemia.
Lerouet
Dominique
D
Laboratoire de Pharmacologie (UPRES EA 2510), Université René Descartes, 4 avenue de l'Observatoire, 75006 Paris, France.
Jafarian-Tehrani
Mehrnaz
M
Louin
Gaëlle
G
Palmier
Bruno
B
Bonnefont-Rousselot
Dominique
D
Plotkine
Michel
M
Margaill
Isabelle
I
D000578:Amidines / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000925:Anticoagulants / Q000627:therapeutic use; D001596:Benzylamines / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004492:Edetic Acid / Q000627:therapeutic use; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D002546:Ischemic Attack, Transient / Q000188:drug therapy / Q000201:enzymology*; D008297:Male; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000188:drug therapy / Q000473:pathology; D013997:Time Factors
C102136:ARL 17477; D000578:Amidines; D000925:Anticoagulants; D001596:Benzylamines; D004791:Enzyme Inhibitors; C104820:N-(3-(aminomethyl)benzyl)acetamidine; D004492:Edetic Acid; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D002118:Calcium