D-arginine action against neurotoxicity induced by glucocorticoids in the brain

Glucocorticoids (GC) are necessary for normal life but elevated levels of GC have been implicated in the development of several neurological diseases and psychiatric disorders. Nowadays, it is well known that high levels of GC in the central nervous system (CNS) generate an increase in the production of reactive oxygen species (ROS), derived mainly from the nitric oxide (NO) pathway. Accordingly, there is an increase of l-arginine (l-Arg.) availability. This report reviews the evidence that d-arginine (d-Arg.) induces normalization of l-Arg. resulting in protection against GC neurotoxic actions in the hippocampus. It is important to highlight that this D-amino acid does not interfere with the expected peripheral effects of GC such as suppression of the hypothalamic-pituitary-adrenal axis (HPA axis) and the immune response, commonly used in clinical practice.     

Involvement of nitric oxide in 5-HT3 receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats

Objectives:

The aim of the present study was to investigate the involvement of nitric oxide in 5-HT₃ receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats.

Materials and Methods:

Fluid movement in jejunum and colon were determined simultaneously in the same rat, by modifying the Beubler method. Nω-nitro-L-arginine (L-NNA, 20 mg/kg, s.c) alone and in combination with L-arginine (L-Arg, 150 mg/kg s.c) or D-arginine (D-Arg, 150 mg/kg, s.c) were administered 30 min before administration of 1-PBG (18.5 μg/kg, i.v).

Results:

Intravenous administration of 1-phenylbiguanide (1-PBG) induced a net secretion of fluid in both jejunum and colon. 1-PBG had a more prominent secretory effect in the colon, causing a three-fold increase in volume of fluid secreted/g of colon than in the jejunum. Pretreatment with (L-NNA) prevented the 1-PBG-induced fluid accumulation in both jejunum and colon. The inhibitory effect of L-NNA on 1-PBG-induced fluid accumulation was reversed by L-Arg but not by D-Arg.

Conclusion:

These results provide evidence that nitric oxide plays an important role in 5-HT₃ receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats.     

The Hermansky-Pudlak syndrome: Variable reaction to 1-desamino-8D-arginine vasopressin for correction of the bleeding time

The effect of the synthetic vasopressin derivative l-desamino-8D-arginine vasopressin (DDAVP = Minrin) on bleeding time was studied in nine patients with Hermansky-Pudlak syndrome; four of them were Dutch, five were Belgian. Shortening of bleeding time was observed in four of the patients with this type of storage pool disease; in one patient the response was equivocal, in two patients the response was not dramatic and in two there was no response at all. DDAVP may be useful in managing the bleeding disorder in some patients with Hermansky-Pudlak syndrome. Therefore, every patient with this syndrome should be tested with DDAVP as a preventive measure.     

Hermansky-Pudlak syndrome: correction of bleeding time by 1-desamino-8D-arginine vasopressin

The effect of the synthetic vasopressin derivative 1-desamino-8D-arginine vasopressin (DDAVP = desmopressin) on bleeding time was studied in three patients with Hermansky Pudlak syndrome. A good response was observed in this type of storage pool disease. DDAVP might be useful in managing the bleeding disorder found in patients with the Hermansky-Pudlak syndrome.