Evaluation of the Effects of Bile on the Arterial Tonus in a Rabbit Model.

BACKGROUND: Hepatic artery anastomosis is an essential part of live-donor liver transplantation, and during this anastomosis, an unusual contact between bile and vessel ends is observed. In this study, the effects of this nonphysiological contact in a rabbit model were evaluated. METHODS: The study was designed in 2 steps-in vitro and in vivo. Three groups were established for the in vitro study. In the first group, vessels were incubated in Krebs solution with 5% bile for 1 minute. In the second group, vessels were kept in Krebs solution with 5% bile for 5 minutes. Vessels in the control group were kept in Krebs solution without bile. All groups were examined for responses to vasodilator and vasoconstrictor agents in organ bath system. The specimens were evaluated immunohistochemically and histopathologically. In the in vivo step, microvascular anastomosis was performed bilaterally. Right carotid artery was anastomosed during bile contamination as study group, and left carotid artery was anastomosed without bile contamination as control group. Blood flow indexes were measured. RESULTS: The results of the in vitro study revealed decreased responses to contractile and relaxing agents in the first study group compared with that of the control group (P < 0.0001). There was no response obtained in the second study group. The Doppler ultrasound results revealed no difference between preoperative and postoperative flow indexes (P > 0.05). There was no postoperative spasm in the study group. However, there was significant vasospasm in the control group (P < 0.05). CONCLUSIONS: Vessels exposed to bile have decreased contractile and relaxing responses, and this effect increases with exposure duration.

Reversal of doxorubicin-induced vascular dysfunction by resveratrol in rat thoracic aorta: Is there a possible role of nitric oxide synthase inhibition?

OBJECTIVE: The natural antioxidant, resveratrol has been suggested to protect against doxorubicin-induced cardiotoxicity. Although derangements in nitric oxide (NO) synthesis contribute to vascular endothelial dysfunction caused by doxorubicin, the effects of resveratrol on these parameters have not been evaluated yet. We investigated the impact of resveratrol on doxorubicin-induced vascular dysfunction in rat thoracic aorta with regard to NO synthesis in an experimental, prospective, controlled study. METHODS: Wistar rats were assigned to 5 groups; doxorubicin (n=9), vehicle (dimethylsulphoxide) (n=8), resveratrol (n=8), doxorubicin+resveratrol (n=10), controls (n=9). Contractile and relaxant responses were evaluated on the isolated thoracic aortas. The expressions of endothelial (eNOS) and inducible (iNOS) isoforms of NO-synthase were also examined histopathologically on the aortas. Statistical analysis was performed by ANOVA for repeated measures for the response curves and one-way ANOVA for the pD2 (-log EC50) and Emax (maximum phenylephrine contraction) values with subsequent Bonferroni test. RESULTS: Doxorubicin (20 mg/kg, i.p), not only decreased the contractile responses to phenylephrine (p<0.001), but also attenuated the relaxant responses to acetylcholine (ACh) (p=0.002), calcium ionophore (A23187) (p=0.002) and sodium nitroprusside (SNP) (p=0.007). Immunohistochemistry revealed increased (p<0.05) eNOS and iNOS protein expressions after doxorubicin treatment. Coadministration of resveratrol (10 mg/kg/i.p.) reversed the increased expression of both NOS isoforms (p<0.05). Similarly, it prevented the doxorubicin-induced attenuation in ACh- (p=0.013) and A23187- (p=0.038) induced responses. In healthy rats the antioxidant did not cause significant changes. CONCLUSION: Prevention of excessive NO formation through eNOS and iNOS overexpression by resveratrol might contribute to the reversal of vascular endothelial dysfunction associated with doxorubicin treatment.

Methylenetetrahydrofolate reductase C677T and A1298C gene polymorphisms and therapy-related toxicity in children treated for acute lymphoblastic leukemia and non-Hodgkin lymphoma.

This study aimed to investigate the association of the methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms with serum drug levels and toxicities after high-dose methotrexate (MTX) infusion. The study included 37 children with acute lymphoblastic leukemia or non-Hodgkin lymphoma. Serum MTX levels and toxicities of bone marrow, liver and kidney were analysed. Genotype analysis of the C677T and A1298C gene polymorphisms from genomic DNA of the subjects was performed by real-time PCR. Subjects with MTHFR polymorphism for C677T (CT, TT) had significantly higher MTX levels at 24 h (p = 0.009), and these genotypes did not seem to cause toxicity. Subjects with MTHFR polymorphism for A1298C (AC, CC) had significantly higher MTX levels at 48 h (p = 0.02), and had more grade III/IV anemia (p = 0.02), thrombocytopenia (p = 0.0001), elevated AST levels (p = 0.04) and frequent febrile neutropenic episodes (p = 0.004). The present study suggests that A1298C gene, but not C677T polymorphism is associated with MTX-related toxicity.

Pharmacologic targets on the female urethra.

INTRODUCTION: This article reviews the mechanisms affecting contraction and relaxation of the urethra in order to establish a basis for current and future treatments for urinary incontinence in women. MATERIAL AND METHODS: A review of the English literature using MEDLINE was performed between 1970 and 2008 on female urethra pharmacology, urinary incontinence, and mechanisms involved in contraction and relaxation of the female human urethra. RESULTS: alpha-Adrenoceptors (ARs) cause contraction and beta-ARs cause relaxation. Use of selective alpha-agonist and beta-AR blocker agents might have potential for the treatment of stress urinary incontinence. Tolerable doses of cholinergic agonists did not have significant effects on intraurethral pressure. Nitric oxide seems to be the major nonadrenergic-noncholinergic inhibitory transmitter causing relaxation. c-kit-positive interstitial cells seem to regulate urethral tone. The roles of adenosine triphosphate and carbon monoxide have not been fully investigated in humans. Neuropeptides function similarly to the urinary bladder. Prostanoids cause urethral contraction and relaxation depending on their subtypes. Serotonin enhances the strength of urethral sphincteric contractions. The Rho-kinase pathway also appears to be modulating smooth muscle contraction in the urethra. CONCLUSIONS: Understanding of the urethral function and pharmacology may lead to the development of promising new agents which might be useful in the management of urinary incontinence in women.

Therapeutic concentrations of tacrolimus do not interfere with endothelial nitric oxide synthesis in rat thoracic aortas and coronary arteries.

This study aimed to investigate the potential effect of in vivo administration of immunosuppressive agent FK-506 (tacrolimus) on the endothelial function of rat thoracic aortas with respect to nitric oxide (NO) synthesis. In vitro effect of the drug on NO synthesis in cultured rat coronary microvascular endothelial cells (CMEC) was also studied.In vivo administration of tacrolimus (1 mg/kg/d, intramuscular) to rats for 14 days resulted in decreased relaxant responses to the higher concentrations (1 to 30 muM) of acetylcholine in the aortas; however, responses to calcium ionophore A23187, sodium nitroprusside, L-arginine, and L-NAME did not change significantly. No changes were observed in phenylephrine-induced contractions in endothelium-denuded or -intact preparations. Administration of the vehicle for 14 days did not affect these parameters. In order to evaluate the in vitro effect of tacrolimus on NO release, CMEC isolated from rat hearts were incubated with either tacrolimus (0.01, 0.1 microM) or the vehicle. Basal, calcium ionophore-stimulated, or interleukin-1 beta-induced NO synthesis was determined by measuring total nitrite in the media. Neither tacrolimus nor the vehicle changed nitrite accumulation. It has been concluded that therapeutic concentrations of tacrolimus do not alter NO production in rat thoracic aorta or cultured CMEC; however, it impairs relaxant responses of rat aorta induced by higher concentrations of acetylcholine, possibly through changes in the downstream of receptor activation or through an imbalance between endothelium-dependent relaxant and contracting factors within the endothelium in favor of the contracting factor(s).

Role of Rho-kinase in contractions of ureters from rabbits with unilateral ureteric obstruction.

OBJECTIVE: To investigate the expression of two isoforms of Rho-kinase (ROCK) and its functional role in the pathophysiological control of smooth muscle contraction in rabbits with unilateral ureteric obstruction (UUO). MATERIAL AND METHODS: Left UUO was created in 14 rabbits and eight other rabbits (controls) had sham operations. After 2 weeks all the rabbits were killed. Ureteric strips suspended in an organ bath were used for functional studies and the effects of Y-27632, a specific inhibitor of Rho-kinase, on spontaneous contractions and electrical field stimulation (EFS; 50 V, 1 ms, 16 Hz, for 20 s), carbachol- (10(-7)-10(-4)m), phenylephrine- (10(-7)-10(-4)m) and KCl- (50 mm) induced contractions were analysed. Western blotting was used to determine expression levels of Rho-kinase protein in the ureters of UUO and control rabbits. RESULTS: In the functional analysis, the contractions induced by EFS, KCl, phenylephrine and carbachol in the ureteric strips from rabbits with UUO were significantly greater than those from the control rabbits. Y-27632 considerably suppressed the ureter contractile responses in both UUO and control rabbits. Western blot analysis showed that both ROCK-1 and ROCK-2 proteins were expressed in the rabbit ureter. In accordance with the functional studies, the expression levels of both ROCK-1 and ROCK-2 were significantly greater in the ureters of UUO rabbits than in the controls. CONCLUSIONS: Y-27632 suppressed ureteric contractions in the rabbits with UUO. Western blot analysis also confirmed greater expression levels of ROCK-1 and ROCK-2 in the ureters of UUO rabbits. It is important to elucidate by which mechanisms the Rho-kinase pathway affects ureteric function after obstruction.

Effect of homocysteine on nitric oxide production in coronary microvascular endothelial cells.

Hyperhomocysteinemia is widely recognized as an independent risk factor for coronary artery vascular disease, although the underlying mechanisms are not well understood. This study aims to investigate the effect of homocysteine on nitric oxide (NO) production in coronary microvascular endothelial cells (CMECs) and putative mechanisms mediating this effect. CMECs were isolated on Langendorff system by collagenase perfusion of hearts from male rats and cultured. The effect of homocysteine (0.01 to 1 mM) on basal and stimulated NO production was evaluated by measuring nitrite in the culture media after incubation with or without N(G)-nitro-L-arginine methyl ester (L-NAME) (1 mM), superoxide dismutase (100 U/mL), or catalase (1000 U/mL) for 24 h. Total nitrite was measured using Griess reaction after reduction of nitrate to nitrite with nitrate reductase. Homocysteine did not affect basal nitrite accumulation; however, it significantly increased the nitrite accumulation induced by the calcium ionophore A23187 or interleukin-1beta only at 1 mM. This effect of homocysteine was significantly inhibited by L-NAME, superoxide dismutase, and catalase. In conclusion, homocysteine increases NO release from stimulated CMECs without affecting basal NO production, which is probably accompanied by increased production of reactive oxygen species. It can be postulated that endothelial cells generate NO in order to minimize the damage caused by homocysteine.

Vascular endothelial dysfunction associated with elevated serum homocysteine levels in rat adjuvant arthritis: effect of vitamin E administration.

We aimed to study the alterations in serum homocysteine levels and endothelium-dependent and -independent vascular relaxant responses in adjuvant-induced arthritis of the rat and to determine the effects of vitamin E administration on these changes. Arthritis was induced by a single intradermal injection of Freund's complete adjuvant into the paw. 26 days after the induction of arthritis, serum homocysteine levels and relaxant responses to acetylcholine and sodiumnitroprusside in thoracic aortas were evaluated. The relaxant responses to acetylcholine were decreased in aortas from arthritic rats, whereas the responses to sodiumnitroprusside were not significantly different when compared to the aortas from control rats. A significant increase was observed in serum homocysteine levels of the arthritic rats in comparison to those of controls. Vitamin E administration (100 mg/kg/day, i.m. for 26 days) to arthritic rats resulted in a significant increase in endothelium-dependent aortic responses to acetylcholine and a significant decrease in serum homocysteine levels with respect to the non-treated arthritic rats. However, in healthy rats, vitamin E treatment significantly decreased the acetylcholine-induced relaxant responses. We conclude that adjuvant-induced arthritis in the rat is associated with increased serum homocysteine levels and this is accompanied by a reduction in endothelium-dependent vascular responses in the thoracic aortas. Vitamin E treatment leads to normalization of the increased serum homocysteine levels and improves the endothelium-dependent relaxant responses in this experimental model.