Effects of Leptin on Hydrogen Peroxide Induced Contractions in Isolated Human Umbilical Artery

\n Objective: In this study, effects of   leptin on  hydrogen peroxide induced  contractions, basal tone of umbilical artery and role of nitric oxide were examined.

\n Materials and methods: Umbilical artery rings were placed in tissue bath containing Krebs-Henseleit Solution (KHS) gassed with %95 O₂ and %5 CO₂ at 37°C. Responses to the applied procedures were recorded isometrically.

\n Results: In the part where the effects of leptin on basal tonus of umbilical artery rings were investigated, cumulative leptin (10^-11-10^-7 M) did not affect basal tonus of tissues. Similarly, the cumulative leptin addition on tissues incubated with L-NAME (10^-4 M) did not affect the basal tonus of the tissues. Cumulatively administered leptin in tissue bath after receiving maximal contraction with H₂O₂ (10^-3 M) on the umbilical artery rings produced relaxation responses concentration-dependent. Addition of 10^-4 M L-NAME to the tissue bath did not affect relaxation responses observed at concentrations 10^-11 and 10^-10 M of leptin but significantly inhibited the relaxation responses observed at concentrations 10^-9,10^-8 and 10^-7 M of leptin on the umbilical artery strips on H₂O₂-induced contraction responses. In the part where the effects of H₂O₂ on leptin-induced umbilical artery rings, incubation of the tissues with 10^-10 M and 10^-7 M leptin did not change pD₂ (-log EC₅₀) and Emax values of cumulative applied H₂O₂.

\n Conclusion: These results demonstrate that a relaxant effect on H₂O₂-induced contraction responses in all concentrations of leptin in human umbilical artery and relaxation responses observed at high concentrations of leptin are partially mediated by NO and also demonstrate that leptin does not have an inhibitory effect on H₂O₂-induced contraction responses applied at basal tone and basal tonus levels of umbilical arteries.