Calcium-independent NO-synthase activity and nitrites/nitrates production in transient focal cerebral ischaemia in mice.
1. The temporal changes in constitutive NO-synthase (cNOS) and in calcium-independent NO-synthase activities were studied in mice subjected to 2 h of transient focal cerebral ischaemia. The changes in brain nitrites/nitrates (NOx) content were also studied. 2. NOS activities were measured by the conversion of L-[14C]-arginine to L-[14C]-citrulline. Brain NOx contents were investigated by the Griess colourimetric method. 3. cNOS activity in the infarcted cortical area was significantly reduced after 6 h of reperfusion and this activity remained attenuated for up to 10 days after ischaemia. A calcium-independent NOS activity began to increase 48 h after reperfusion, reached a maximum at 7 days and returned to baseline at 10 days. 4. There was a significant increase of brain NOx content beginning after 3 days of reperfusion. This increase was maximal at 7 days and returned to baseline at 10 days. 5. Thus, ischaemia followed by recirculation leads to a rapid, prolonged drop in cNOS activity in the infarcted cortex. There is also a substantial appearance of calcium-independent NOS activity in the later phase of transient ischaemia, leading to an important increase of NOx production.
Grandati
M
M
Laboratoire de Pharmacologie, Université René Descartes, Paris, France.
Verrecchia
C
C
Revaud
M L
ML
Allix
M
M
Boulu
R G
RG
Plotkine
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006868:Hydrolysis; D002546:Ischemic Attack, Transient / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051379:Mice; D009566:Nitrates / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*
D009566:Nitrates; D009573:Nitrites; D019001:Nitric Oxide Synthase; D002118:Calcium