Bioaccumulation and distribution of Pb, Ni, Zn and Fe in stinging nettle (Urtica dioica) tissues and heavy metal-contamination assessment in the industrial zone of smelter Ferronikeli (Drenas-Kosovo).

Here, we determined the concentrations of Pb, Ni, Zn and Fe in the soil and in vegetative organs of stinging nettle (Urtica dioica) collected from the banks of the Drenica River in the vicinity of the Ferronikeli smelter. The results were compared with samples collected from the banks 20 km (Shalë village) upriver. In addition, the bioaccumulation factor (BCF) and translocation factor (TF) were determined. Meanwhile, to evaluate the level of pollution in the study area was used the contamination factor (CF), potential ecological risk factor (Eri) and the potential ecological risk index (RI). The order of heavy metals according to their concentration in the soil samples at both sampling sites was as follows: Fe > Ni > Zn > Pb. Concentrations in excess of the limits allowed for soils in the samples collected in the vicinity of the smelter were recorded for Pb (173.13 mg kg-1), Zn (1217.48 mg kg-1), and Ni (1443.93 mg kg-1), while at the control site, Zn (270.82 mg kg-1) and Ni (375.47 mg kg-1) were found in excess concentrations. But lead (Pb) level was under allowed limit. The data showed that the stinging nettle is not a hyperaccumulator because BCF < 1 at both sites for all metals under study. Furthermore, analysis of the translocation factor (TFsteam/root) showed that at low of heavy metal concentrations, their mobility was higher (TF > 1). The lowest mobility (TF < 1) was observed at site I (Poklek), where the concentration of heavy metals was higher, except for Fe. The opposite was shown for mobility of metals from stems to leaves (TFleave/steam). The evaluation of CF showed that the area near the Ferronikeli smelter had low degree of Pb, moderate degree of Zn and considerable degree of Ni contamination. The values of RI indicate low potential ecological risk index.

L-citrulline supplementation reverses the impaired airway relaxation in neonatal rats exposed to hyperoxia.

BACKGROUND: Hyperoxia is shown to impair airway relaxation via limiting L-arginine bioavailability to nitric oxide synthase (NOS) and reducing NO production as a consequence. L-arginine can also be synthesized by L-citrulline recycling. The role of L-citrulline supplementation was investigated in the reversing of hyperoxia-induced impaired relaxation of rat tracheal smooth muscle (TSM). METHODS: Electrical field stimulation (EFS, 2-20 V)-induced relaxation was measured under in vitro conditions in preconstricted tracheal preparations obtained from 12 day old rat pups exposed to room air or hyperoxia (>95% oxygen) for 7 days supplemented with L-citrulline or saline (in vitro or in vivo). The role of the L-citrulline/L-arginine cycle under basal conditions was studied by incubation of preparations in the presence of argininosuccinate synthase (ASS) inhibitor [α-methyl-D, L-aspartate, 1 mM] or argininosuccinate lyase inhibitor (ASL) succinate (1 mM) and/or NOS inhibitor [Nω-nitro-L-arginine methyl ester; 100 µM] with respect to the presence or absence of L-citrulline (2 mM). RESULTS: Hyperoxia impaired the EFS-induced relaxation of TSM as compared to room air control (p < 0.001; 0.5 ± 0.1% at 2 V to 50.6 ± 5.7% at 20 V in hyperoxic group: 0.7 ± 0.2 at 2 V to 80.0 ± 5.6% at 20 V in room air group). Inhibition of ASS or ASL, and L-citrulline supplementation did not affect relaxation responses under basal conditions. However, inhibition of NOS significantly reduced relaxation responses (p < 0.001), which were restored to control level by L-citrulline. L-citrulline supplementation in vivo and in vitro also reversed the hyperoxia-impaired relaxation. The differences were significant (p <0.001; 0.8 ± 0.3% at 2 V to 47.1 ± 4.1% at 20 V without L-citrulline; 0.9 ± 0.3% at 2 V to 68.2 ± 4.8% at 20 V with L-citrulline). Inhibition of ASS or ASL prevented this effect of L-citrulline. CONCLUSION: The results indicate the presence of an L-citrulline/L-arginine cycle in the airways of rat pups. L-citrulline recycling does not play a major role under basal conditions in airways, but it has an important role under conditions of substrate limitations to NOS as a source of L-arginine, and L-citrulline supplementation reverses the impaired relaxation of airways under hyperoxic conditions.