Metabolic study of trimetazidine using ultra-high performance liquid chromatography-tandem mass spectrometry

Abstract In the present study, the application of ultra-high performance liquid chromatography-tandem mass spectrometry allowed us to study of known-as well as hitherto unknown-trimetazidine (TMZ) metabolites in human urine and to propose their renal excretion profiles. Urine samples from a healthy volunteer were analyzed at baseline and at 0-4 h, 4-8 h, 8-12 h, and 12-24 h after a single dose of TMZ. A dilute-and-shoot procedure was used as sample treatment before separation. Full-scan spectra of possible metabolites were acquired. Additionally, product ion scan spectra of precursor ions of interest were also acquired at two collision energies. Intact TMZ was a major excretion product, with a maximum concentration at 4-8 h after administration. Moreover, five minor metabolites were observed, namely trimetazidine-N-oxide (M1), N-formyl trimetazidine (M2), desmethyl-trimetazidine O-sulfate (M3), desmethyl-trimetazidine O-glucuronide (M4), and desmethyl-trimetazidine-N-oxide-O-glucuronide (M5). Metabolite M5 has not previously been reported. Excretion curves were constructed based on the chromatographic peak areas of specific mass transitions (precursor ion > product ion) related to each of the detected metabolites

Acutely applied melatonin prevents CCl4-induced testicular lesions in rats: the involvement of the oxidative capacity and arginine metabolism

Abstract Carbon tetrachloride (CCl4) represents an organic chemical that causes reactive oxygen species derived organ disturbances including male infertility. Melatonin (MLT) is a neurohormone with strong antioxidant capacity, involved in numerous physiological processes. In this study we evaluated the capability of MLT, administered in a single dose of 50 mg/kg, to preserve the testicular tissue function after an acute administration of CCl4 to rats. The disturbance in testicular tissue and the effects of MLT after CCl4 exposure were estimated using biochemical parameters that enabled us to determine the tissue (anti)oxidant status and the intensity of arginine/nitric oxide metabolism. Also, the serum levels of testosterone and the histopathological analysis of tissue gave us a better insight into the occurring changes. A significant diminution in tissue antioxidant defences, arginase activity and serum testosterone levels, followed by the increased production of nitric oxide and extensive lipid and protein oxidative damage, was observed in the CCl4-treated group. The application of MLT after the CCl4 caused changes, clearly visible at both biochemical and histological level, which could be interpreted mainly as a consequence of general antioxidant system stimulation and a radical scavenger. On the other hand, the application of MLT exerted a limited action on the nitric oxide signalling pathway.

Do avanafil and zaprinast exert positive effects on bone tissue via the nitric oxide/cyclic guanosine monophosphate/protein kinase-G signaling pathway in rats with ovariectomy-induced osteoporosis?

Phosphodiesterase-5 inhibitors (PDE-5Is) exert positive effects on bone healing and mineralization by activation the nitric oxide/cyclic guanosine monophosphate/protein kinase-G (NO/cGMP/PKG) signaling pathway. In this study, the effects of zaprinast and avanafil, two PDE-5Is, on the NO signaling pathway, estrogen levels, selected bone formation and destruction marker levels, whole-body bone mineral density (WB-BMD), right femur trabecular bone thickness (RF-TBT) and epiphyseal bone width, angiogenesis in the bone-marrow, and selected oxidative stress parameter levels were investigated in rats with ovariectomy-induced osteoporosis. Twenty four adult rats (8 months old) were equally divided into four groups. The first group was the sham operated group. Groups 2, 3 and 4 included ovariectomized rats. At six months after ovariectomy, the 3rd and 4th groups were administered 10 mg/kg zaprinast and avanafil daily as a single dose for 60 days, respectively. Increases in the activity of the NO/cGMP/PKG signalling-pathway, C-terminal collagen peptide levels, angiogenesis in the bone marrow, RF-TBT, epiphyseal bone width and WB-BMD were observed compared to the ovariectomized positive control group (OVX), while the pyridinoline and deoxypyridinoline levels were decreased in the OVX+zaprinast and OVX+avanafil groups (p<0.05). The malondialdehyde, ubiquinone10/ubiquinol10 and 8-hydroxy-2-deoxyguanosine/106deoxyguanosine levels were also increased in the ovariectomized groups compared to the sham group (p<0.05). Based on these results, the levels of bone atrophy and some markers of oxidative stress were increased due to acute estrogen deficiency induced by ovariectomy, but zaprinast and avanafil administration significantly prevented these changes

L-arginine, a nitric oxide precursor, reduces dapsone-induced methemoglobinemia in rats

Dapsone use is frequently associated to hematological side effects such as methemoglobinemia and hemolytic anemia, which are related to N-hydroxylation mediated by the P450 enzyme system. The aim of the present study was to evaluate the influence of L-arginine supplementation, a precursor for the synthesis of nitric oxide, as single or multiple dose regimens on dapsone-induced methemoglobinemia. Male Wistar rats were treated with L-arginine at 5, 15, 30, 60 and 180 mg/kg doses (p.o., gavage) in single or multiple dose regimens 2 hours prior to dapsone administration (40 mg/kg, i.p.). The effect of the nitric oxide synthase inhibitor L-NAME was investigated by treatment with multiple doses of 30 mg/kg (p.o., gavage) 2 hours before dapsone administration. Blood samples were collected 2 hours after dapsone administration. Erythrocytic methemoglobin levels were assayed by spectrophotometry. The results showed that multiple dose supplementations with 5 and 15 mg/kg L-arginine reduced dapsone-induced methemoglobin levels. This effect is mediated by nitric oxide formation, since the reduction in methemoglobin levels by L-arginine is blocked by simultaneous administration with L-NAME, a nitric oxide synthase inhibitor.

O uso da dapsona é frequentemente associado a efeitos adversos hematológicos, como a metemoglobinemia e anemia hemolítica, ambos relacionados com a N-hidroxilação mediada pelo sistema P450. O objetivo do estudo foi avaliar a influência da suplementação de L-arginina, um precursor da síntese de óxido nítrico, administrado em regime de dose única ou múltipla na metemoglobinemia induzida pela dapsona. Ratos machos Wistar foram tratados com L-arginina (po, gavagem) em dose única ou múltipla de 5, 15, 30, 60 e 180 mg/kg 2 horas antes da administração de dapsona (40 mg/kg, ip). O efeito do L-NAME, um inibidor de óxido nítrico sintase (NOS), foi avaliado através do tratamento com doses múltiplas de 30 mg/kg. Amostras de sangue foram coletadas duas horas após a administração de dapsona. A concentração de metemoglobina eritrocitária foi analisada por espectrofotometria. Os resultados mostraram que a suplementação em dose múltipla de 5 e 15 mg/kg de L-arginina reduziu os níveis de metemoglobina induzida pela dapsona. Este efeito é mediado pela formação de óxido nítrico, uma vez que a redução nos níveis de metemoglobina pela L-arginina é bloqueada pela administração simultânea de L-NAME, um inibidor da óxido nítrico sintase.