Effects of L-arginine oral supplements in pregnant spontaneously hypertensive rats

Pathophysiology of Preeclampsia and L-Arginine/L-Citrulline Supplementation as a Potential Strategy to Improve Birth Outcomes

In preeclampsia, the shallow invasion of cytotrophoblast cells to uterine spiral arteries, leading to a reduction in placental blood flow, is associated with an imbalance of proangiogenic/antiangiogenic factors to impaired nitric oxide (NO) production. Proangiogenic factors, such as vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), require NO to induce angiogenesis through antioxidant regulation mechanisms. At the same time, there are increases in antiangiogenic factors in preeclampsia, such as soluble fms-like tyrosine kinase type 1 receptor (sFIt1) and toll-like receptor 9 (TLR9), which are mechanism derivates in the reduction of NO bioavailability and oxidative stress in placenta.Different strategies have been proposed to prevent or alleviate the detrimental effects of preeclampsia. However, the only intervention to avoid the severe consequences of the disease is the interruption of pregnancy. In this scenario, different approaches have been analysed to treat preeclamptic pregnant women safely. The supplementation with amino acids is one of them, especially those associated with NO synthesis. In this review, we discuss emerging concepts in the pathogenesis of preeclampsia to highlight L-arginine and L-citrulline supplementation as potential strategies to improve birth outcomes. Clinical and experimental data concerning L-arginine and L-citrulline supplementation have shown benefits in improving NO availability in the placenta and uterine-placental circulation, prolonging pregnancy in patients with gestational hypertension and decreasing maternal blood pressure.

Protective effect of nicotinamide and L-arginine against monocrotaline-induced pulmonary hypertension in rats: gender dependence

Background

The purpose of this paper was to examine the effects of nicotinamide (ND) and l-arginine (l-ARG) on pulmonary vascular and heart changes induced by pulmonary hypertension in rats in a gender-dependent way.

Methods

Experiments were performed on male (M) and female (F) rats. PAH was induced via monocrotaline injection (sc, 60/kg B.W.) on day one of the 23-day observational period. After that, the animals were sacrificed, hearts removed and weighed and the papillary muscles isolated to measure force of contraction (F_c). Morphological changes of pulmonary vessels were also examined.

Results

Mixed diet supplementation with l-ARG + ND prevented highly significant right ventricle enlargement induced by PAH in both, male and female rats. Weight ratios between the right ventricle (RV) on one side and the left ventricle with septum on the other (LV + S) decreased from 0.46 ± 0.016 g to 0.29 ± 0.006 g in males and from 0.63 ± 0.03 g to 0.24 ± 0.008 g in females, n = 6, p < 0.001. Additionally, PAH increased basal contractility in female groups, and each of the diet allocations (l-ARG, ND, and mixed) were found to restore contractility to control values. All diet protocols in male and female restored decreased responsiveness of the myocardium to norepinephrine in hearts obtained from rats with PAH and prevented vascular changes observed in pulmonary hypertension (thickness of blood vessels and cell infiltration).

Conclusion

Our study suggests that l-arginine, nicotinamide or both play a positive role in right ventricle function or the process reducing pulmonary vascular remodeling especially in a gender-independent way.

Nutritional supplementation with arginine protects radiation-induced effects. An experimental study

PURPOSE:

To investigate the protective effect of L-arginine on the prostate (nonneoplasic) of rats with radiation-induced injury.

METHODS:

Twenty-nine Wistar rats, male adult, allocated into three groups: Control group (C) was not exposed to irradiation (n=10); Radiated group (R) had undergone pelvic irradiation (n=10); Supplemented and radiated group (R+S) had undergone pelvic irradiation plus L-arginine supplementation (n=9). The animals were observed for signs of toxicity. After euthanization, the prostate was dissected under magnification and stained by hematoxylin and eosin to study acinar structures and stained with Picrosirius red for collagen analysis.

RESULTS:

After radiation exposure, all animals presented diarrhea, but supplementation with L-arginine reduced this effect. The weight gain in the R+S group was significantly higher than in the C and R groups. In the R+S group the collagen density and the prostate acinar area was similar to the R and C groups. Epithelial height was significantly reduced in group R compared with group C (p<0.0001). When comparing the group R+S with R, a statistical difference was observed to be present (p<0.0001).

CONCLUSIONS:

Pelvic radiation promotes systemic effects and some structural modifications in the ventral prostate of rats. These modifications can be prevented by oral supplementation with L-arginine.

Role of nitric oxide deficiency in the development of hypertension in hydronephrotic animals

Hydronephrotic animals develop renal injury and hypertension, which is associated with an abnormal tubuloglomerular feedback (TGF). The TGF sensitivity is coupled to nitric oxide (NO) in the macula densa. The involvement of reduced NO availability in the development of hypertension in hydronephrosis was investigated. Hydronephrosis was induced by ureteral obstruction in young rats. Blood pressure and renal excretion were measured in adulthood, under different sodium conditions, and before and after chronic administration of either NG-nitro-l-arginine methyl ester (l-NAME) or l-arginine. Blood samples for ADMA, SDMA, and l-arginine analysis were taken and the renal tissue was used for histology and determination of NO synthase (NOS) proteins. TGF characteristics were determined by stop-flow pressure technique before and after administration of 7-nitroindazole (7-NI) or l-arginine. Hydronephrotic animals developed salt-sensitive hypertension, which was associated with pressure natriuresis and diuresis. The blood pressure response to l-NAME was attenuated and l-arginine supplementation decreased blood pressure in hydronephrotic animals, but not in the controls. Under control conditions, reactivity and sensitivity of the TGF response were greater in the hydronephrotic group. 7-NI administration increased TGF reactivity and sensitivity in control animals, whereas, in hydronephrotic animals, neuronal NOS (nNOS) inhibition had no effect. l-Arginine attenuated TGF response more in hydronephrotic kidneys than in controls. The hydronephrotic animals displayed various degrees of histopathological changes. ADMA and SDMA levels were higher and the renal expressions of nNOS and endothelial NOS proteins were lower in animals with hydronephrosis. Reduced NO availability in the diseased kidney in hydronephrosis, and subsequent resetting of the TGF mechanism, plays an important role in the development of hypertension.