l-Arginine is unlikely to exert neuroendocrine effects in humans via the generation of nitric oxide

Korbonits, M; Trainer, Peter; Fanciulli, Giuseppe; Oliva, Osvaldo; A, Pala; Dettori, Alessandra; Besser, Michael; Delitala, G.; Grossman, Ashley

doi:10.1530/eje.0.1350543

Cited by 28 publications

(18 citation statements)

References 16 publications

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“…Previous experiments have also reported a decrease in serum LH concentrations after systemic administration of L-AME (4). A recent study in humans has reported that the administration of L-AME was ineffective in modifying serum LH concentrations (27). However, in this study, the dose was about 0.4 g/kg bw, which is lower than the minimal effective dose in the rat.…”

Section: Discussioncontrasting

confidence: 62%

Role of the testis in the response of the pituitary-testicular axis to nitric oxide-related agents

Gaytán

Bellido²,

Aguilar³

et al. 1997

European Journal of Endocrinology

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Nitric oxide (NO) is generated from the guanidine group of L-arginine by NO synthases (NOS) in a wide variety of tissues, including endocrine organs. In order to discriminate between central and local effects of NO-related agents on the pituitary-testicular axis, adult rats were injected intraperitoneally with 1 g/kg body weight (bw) L-arginine methyl ester (L-AME, an exogenous substrate of NOS), 0.5 mg/kg bw sodium nitroprusside (SNP, an NO donor) or vehicle (0.9% NaCl) or intratesticularly with 2 mg/testis L-AME, 2 mg/testis SNP or 25 ml vehicle, and killed at 60 or 120 min after treatment. Both intraperitoneal and intratesticular administration of L-AME had the same effects: a decrease in the serum concentrations of LH and testosterone and in those of testosterone in the testicular interstitial fluid. However, treatment with SNP was more effective when given intratesticularly, inducing a decrease in serum and interstitial fluid testosterone concentrations, without significant changes in LH concentrations. Furthermore, when rats were injected intraperitoneally with 4 mg L-AME (the same dose as that given intratesticularly), serum LH concentrations were not changed. In addition, L-AME administration was not effective in modifying serum LH concentrations in castrated rats. To test the possible role of Leydig cells, the effects of systemic administration of L-AME were studied in rats depleted of Leydig cells by treatment with ethylene dimethane sulphonate. In these animals L-AME significantly decreased serum LH concentrations. To study the role of macrophages in this system, rats depleted of testicular macrophages by the liposome-suicide approach were injected intraperitoneally (1 g/kg bw) or intratesticularly (2 mg/testis) with L-AME or vehicle, 10 days after macrophage depletion, and killed at 120 min after treatment. The effects of L-AME on serum LH concentrations were blocked when the drug was administered intratesticularly.

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Section: Discussioncontrasting

confidence: 62%

Role of the testis in the response of the pituitary-testicular axis to nitric oxide-related agents

Gaytán

Bellido²,

Aguilar³

et al. 1997

European Journal of Endocrinology

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“…The infusion of L-arginine enhanced plasma growth hormone [34] and glucagon levels [35]. Since these hormones are known to facilitate lipolysis, L-arginine supplementation may possibly affect fat metabolism in skeletal muscle.…”

Section: Discussionmentioning

confidence: 99%

L-Arginine Supplementation Causes Additional Effects on Exercise-Induced Angiogenesis and VEGF Expression in the Heart and Hind-Leg Muscles of Middle-Aged Rats

Suzuki

2006

J. Physiol. Sci

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Abstract:The effects of dietary L-arginine supplementation on exercise-induced angiogenesis and VEGF expression were examined in male middle-aged (12 months old) Wistar rats. Exercise training lasted for six weeks at 20 m/min on a 0% gradient for 10-60 min/day. Rats in the L-arginine-treated groups drank water containing 2.5% L-arginine. According to histochemical identification of the capillary profile, in the soleus muscle the capillary-to-fiber (C:F) ratio showed a significantly greater value in the L-arginine-treated training group than in both the sedentary control and training groups. Training with L-arginine significantly increased the C:F ratio in the subendocardium of the left ventricle, whereas training alone did not. In the plantaris muscle, training with or without L-arginine significantly increased the capillary density, but it did not affect the C:F ratio. A Western blot analysis showed that training with L-arginine significantly increased VEGF protein expression by 2.9-fold in the soleus muscle and by 1.7-fold in the left ventricle, but the increase with training alone was insignificant. The tissue endothelial nitric oxide synthase protein levels were significantly increased in both the soleus (by 1.3-fold) and the left ventricle (by 1.4-fold) only after training with L-arginine supplementation. In the plantaris muscle, these protein levels did not change after either training or L-arginine treatment. The present results suggest that in middle-aged rats, L-arginine administration caused additional effects on exercise-induced angiogenesis by presumably promoting VEGF expression in the hind-leg muscle as well as in the left ventricle.

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“…Nitric oxide is a highly reactive gas that has been suggested to function as a neurotransmitter in the neuroendocrine system [7]including the somatotropic axis [15, 17, 22]. In view of these data, we have reevaluated the role of nitric oxide pathways on canine GH secretion, and more specifically analysed the role played by NO on GHRH, GHRP-6 or sumatriptan-stimulated GH secretion.…”

Section: Discussionmentioning

confidence: 99%

Involvement of Nitric Oxide in the Regulation of Growth Hormone Secretion in Dogs

et al. 2001

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Nitric oxide (NO) is a highly reactive gas that has been suggested to function as a neurotransmitter in the neuroendocrine system. In this work, we have evaluated the role of NO pathways in growth hormone (GH) secretion by assessing the effect of L-arginine infusion, a precursor of NO formation, and L-NAME, a nitric oxide synthase (NOS) inhibitor. The experiments were carried out on 7 adult beagle dogs. A saline infusion was carried out on all the dogs as a control test. L-arginine (infusion i.v. 10 g in 100 ml of saline, from t = 0 to 30 min) and L-nitro-arginine-methyl ester, L-NAME (infusion of 300 µg/kg in 120 ml of saline, from t = –30 to 45 min) were administered alone and together with growth hormone-releasing hormone (GHRH) (i.v. bolus at 0 min, at a dose of 100 µg), the synthetic GH secretagogue GHRP-6 (i.v. bolus at 0 min, at a dose of 90 µg), and the 5-HT1D serotonin receptor agonist sumatriptan, SUM (s.c. injection at the dose of 3 mg). Plasma cGH was determined by RIA. Results were evaluated by one-way analysis of variance, followed by the Newman-Keuls test for multiple comparisons. L-arginine administration resulted in a slight increase in plasma cGH in comparison with saline controls. Combined administration of L-arginine and GHRH enhanced cGH release in comparison with GHRH alone. L-NAME alone did not modify baseline cGH levels, but completely suppressed the GH release induced by GHRH or GHRP-6. It also strongly reduced, but did not abolish the effect of the two peptides (GHRH plus GHRP-6) administered together. Finally, administration of the 5-HT1D agonist SUM induced a significant cGH secretion in all dogs, a response which was not modified when L-NAME was administered in combination with SUM. In conclusion, our data show that inhibition of NO blunts both GHRH or GHRP-6-induced cGH release, and are compatible with the hypothesis that it acts by decreasing hypothalamic somatostatin release.

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l-Arginine is unlikely to exert neuroendocrine effects in humans via the generation of nitric oxide

Cited by 28 publications

References 16 publications

Role of the testis in the response of the pituitary-testicular axis to nitric oxide-related agents

Role of the testis in the response of the pituitary-testicular axis to nitric oxide-related agents

L-Arginine Supplementation Causes Additional Effects on Exercise-Induced Angiogenesis and VEGF Expression in the Heart and Hind-Leg Muscles of Middle-Aged Rats

Involvement of Nitric Oxide in the Regulation of Growth Hormone Secretion in Dogs

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