Cysteine enhancement of cobalt(II)-catalysed chemiluminescence of hydrogen peroxide and luminol occurs in carbonate buffer (but not in borate buffer), whether cysteine mixes with hydrogen peroxide before it mixes with luminol-cobalt(II) or vice versa. Enhancement was measured by the ratio of the signals in the presence and absence of cysteine; standard errors were generally < 5% of the mean ratio. Cystine in sufficiently acidic solution also enhances the chemiluminescence but otherwise diminishes the emission. The emission is also inhibited by glutathione. A mixed solution of cysteine and cystine gives rise to enhanced signals. In all the above cases, enhancement occurs only in the presence of a cobalt(II) catalyst. Luminol-peroxynitrite chemiluminescence is enhanced by cysteine and by glutathione without the presence of a catalyst.

In the present study the role of L-arginine/nitric oxide (NO)/cGMP pathway in the antinociceptive activity of pyridoxine in p-benzoquinone-induced abdominal constriction test in mouse was investigated. Pyridoxine (CAS 58-56-0) displayed dose-dependent antinociceptive activity at 0.0625−1 mg/kg (s.c.) doses. L-arginine (CAS 1119-34-2), a NO precursor, displayed a triphasic pattern as antinociception-nociceptionantinociception (61.8 ± 7.8, −36.5 ± 12.7 and 17.0 ± 4.3 %, 5, 40 and 50 mg/kg, s.c., respectively). The antinociceptive effect of pyridoxine at ED 50 dose (0.43 mg/ kg, s.c.) (47.7 ± 3.9 %) was significantly decreased by L-arginine at 40 and 50 mg/ kg doses (4.1 ± 9.3 and 37.8 ± 1.6 %, respectively) while 5 mg/kg dose of L-arginine significantly potentiated the pyridoxine analgesia. On the other hand, pyridoxine reversed the L-arginine-induced nociception to antinociception (4.1 ± 9.3 %) and augmented the antinociceptive effect of L-arginine (37.8 ± ZusammenfassungDie Rolle von L-Arginin/Stickoxid in der antinozizeptiven Aktivität von Pyridoxin bei Mäusen Ziel dieser Studie war es, die Rolle von L-Arginin/Stickoxid (NO)/cGMP in der antinozizeptiven Aktivität von Pyridoxin im p-Benzochinon.induzierten abdominal Spannungstest zu untersuchen. Pyridoxin (CAS 58-56-0) zeigte eine dosisab-1.6 %). L-N G -nitroarginine methyl ester (CAS 51298-62-5), a NO synthase inhibitor, at 75 mg/kg, s.c. produced antinociception and significantly increased the antinociceptive effect of pyridoxine (63.7 ± 1.2 %). Methylene blue (CAS 61-73-4, MB), a guanylyl cyclase and/or NO synthase inhibitor, was antinociceptive and nociceptive at 5 and 40 mg/kg doses, respectively. 5 mg/kg dose of MB significantly increased the antinociceptive effect of pyridoxine, but did not change it at 40 mg/kg dose. On the other hand, pyridoxine significantly decreased the antinociceptive effect of MB and reversed the MB-induced nociception to antinociception. Combination of pyridoxine and morphine (CAS 57-27-2) (ED 50 : 0.13 mg/kg, s.c.) at 49.8 ± 1.9 % revealed a significant antinociceptive potentiation (69.1 ± 1.8 %). The findings of the present study emphasise the contribution of central and/or peripheral L-arginine/NO/ cGMP nociceptive processes in pyridoxine-induced antinociception. hängige antinozizeptive Aktivität in einer subkutanen Dosis von 0,0625-1 mg/kg. L-Arginin (CAS 1119-34-2), ein NO-Precursor, zeigte ein Drei-Phasen-Muster: Antinozizeption-NozizeptionAntinozizeption ( 61.8 ± 7.8, 36.5 ± 12.7 bzw. 17.0 ± 4.3 %, 5, 40 bzw. 50 mg/kg, s.c.). Der antinozizeptive Effekt von Pyridoxin bei Verwendung der ED 50 (0.43 mg/kg, s.c.) (47.7 ± 3.9) wurde von L-ArgiKey words L-Arginine/NO/cGMP, role in antinociception CAS 58-56-0 CAS 1119-34-2 Pyridoxine, antinociceptive effect, mouse Arzneim.-Forsch./Drug Res. 51 (II), 832−838 (2001) Arzneim.-Forsch./Drug Res. 51 (II), 832−838 (2001) 832 Abacıoglu, et al. − L-Arginine/nitric oxide pathway