Isolation of alpha-n-acetyl-1-arginine from cattle brain

Relationship between structure and inhibitory effect of arginine analogues on neuronal nitric oxide synthase activity

Since nitric oxide (NO) is synthesized by nitric oxide synthase (NOS) from L-arginine (Arg) which has an amidino group in its molecule, we examined the effect of 29 kinds of Arg analogues on neuronal NOS (nNOS) activity in the rat brain. None of the Arg analogues acted as a substrate for nNOS. Diamidinocystamine, hirudonine, and guanethidine inhibited nNOS activity to 67.3%, 64.2% and 74.1%, respectively, but their inhibitory efficiency was lower than NG-monomethyl-L-arginine (to 36.5%) which is a well known NOS inhibitor. Dimethylguanidine and N-benzoylguanidine also significantly inhibited nNOS activity to 88.0% and 90.7%, respectively. Whereas almost all of the NOS inhibitors previously reported were synthesized by substituting the amidino nitrogen of Arg, none of these new inhibitors were substituted at this position. Furthermore, hirudonine, which is a naturally occurring compound, was thought to act as an agonist at polyamine binding site of the N-methyl-D-aspartate type of glutamate receptor complex. It is also interesting that guanethidine, an antihypertensive agent, inhibit nNOS activity. These new drugs are useful for the investigation not only of the chemical nature of nNOS but also of the physiologic function of NO.

Structure-activity relationships of arginine analogues on nitric oxide synthase activity in the rat brain

Nitric oxide (NO) is synthesized by nitric oxide synthase (NOS) from L-arginine (Arg) which has a guanidino group in its molecule. We examined the effect of 23 different Arg analogues on NOS activity in the rat brain. Though homoarginine, epsilon-guanidinocaproic acid and canavanine act as substrates of NOS, production of NO from them was lower than that from Arg. alpha-Guanidinoglutaric acid (2-GGA) and arcaine inhibited NOS activity at levels equal to NG-monomethyl-L-arginine (MeArg), a well known NOS inhibitor. Though almost all previously reported NOS inhibitors were synthesized by substituting the guanidino nitrogen of Arg, the guanidino nitrogens of arcaine and 2-GGA were not substituted. Furthermore, 2-GGA is a known endogenous convulsant in mammals, and arcaine, which was isolated from a marine mollusc, is also a convulsive substance. Hence, 2-GGA and arcaine will be excellent drugs to investigate not only the chemical nature of NOS but also the physiologic function of NO.

Convulsive activity of alpha-guanidinoglutaric acid and the possible involvement of 5-hydroxytryptamine in the alpha-guanidinoglutaric acid-induced seizure mechanism

alpha-Guanidinoglutaric acid (alpha-GGA) was first found in cobalt-induced epileptogenic focus tissue in the cerebral cortex of cats. We examined the effect of alpha-GGA on the electroencephalogram and on the brain 5-hydroxytryptamine (5-HT) level after intraventricular administration into rats. Sporadic low-voltage spikes appeared 4 min after the administration of alpha-GGA. Spikes increased in voltage 6 min after the administration. Multiple spikes appeared 10 min after the administration, and they reached maximal frequency 30 min after the administration. The epileptic discharges disappeared 100 min after the administration. The 5-HT level increased in the right and left cortices 3 min after the administration. The 5-HT level decreased in the mid-brain 5 min after the administration and subsequently in all regions of the brain 10 min after the administration. No change in the 5-HT level was found 30 min and 100 min after the administration. These results show that alpha-GGA induces epileptic seizures in rats after intraventricular administration. The results also suggest that alpha-GGA-induced seizures are associated with abnormal serotonergic function and that they are initiated by a decrease in the 5-HT level.

Fluorometrical analysis of guanidino compounds in human cerebrospinal fluid

Guanidino compounds in CSF of 57 human subjects were determined fluorometrically after reaction with phenanthrenequinone in alkali solution, using HPLC. Creatinine (65.2 +/- 13.4 nmol/ml), arginine (24.7 +/- 6.4 nmol/ml), and homoarginine (0.7 +/- 0.3 nmol/ml) were found in all subjects. Trace amounts of guanidinosuccinic acid and guanidinoacetic acid were detected in some of the subjects. Brain guanidino compounds, taurocyamine, N-acetylarginine, and methylguanidine were not detected in CSF.

A study on the precursors of the acetyl moiety of acetylcholine in brain slices. Observations on the compartmentalization of the acetyl-coenzyme A pool

1. A method was devised for the determination of the specific radioactivity of the acetyl moiety of acetylcholine synthesized from various (14)C-labelled substrates. 2. The precursor for the acetyl moiety of acetylcholine was studied in slices of striatum and cerebral cortex from rat and guinea-pig brain. Incorporation of radioactivity into acetylcholine was determined after incubating the slices in the presence of [2-(14)C]acetate, [(14)C]bicarbonate, [1,5-(14)C]citrate, dl-[1- or 5-(14)C]glutamate or [1- or 2-(14)C]pyruvate. 3. After incubation for 1h, acetylcholine was accumulated significantly in both striatum slices (4.1nmol/mg of protein) and cerebral-cortex slices (0.57nmol/mg of protein) from the rat. Final concentrations were about 11 and 5 times respectively the initial values. 4. With slices from rat striatum, rat cerebral cortex and guinea-pig cerebral cortex, the specific radioactivity of acetylcholine derived from [2-(14)C]pyruvate was very high, reaching approx. 30, 20 and 6% respectively of the initial specific radioactivity of added pyruvate in the medium. With the striatum slices this high value was reached after incubation for 15min. Incorporation of radioactivity from [2-(14)C]acetate was only 1.25, 5.3 and 19.7% of that from [2-(14)C]pyruvate in rat striatum, rat cerebral-cortex and guinea-pig cerebral-cortex slices respectively. A small but definite incorporation was found from [5-(14)C]glutamate. No incorporation was found from the other substrates. The findings suggest that pyruvate is the most important precursor for the synthesis of the acetyl moiety of acetylcholine in brain slices. 5. The specific radioactivity of acetylcholine relative to that of citrate when [2-(14)C]pyruvate was used compared with that obtained when [2-(14)C]acetate was used. A marked difference was found in all slices, suggesting metabolic compartmentation of the acetyl-CoA pool.