Nitric oxide modulates ATP-evoked currents in mouse Leydig cells

Testosterone synthesis within Leydig cells is a calcium-dependent process. Intracellular calcium levels are regulated by different processes including ATP-activated P2X purinergic receptors, T-type Ca2+ channels modulated by the luteinizing hormone, and intracellular calcium storages recruited by a calcium-induced calcium release mechanism. On the other hand, nitric oxide (NO) is reported to have an inhibitory role in testosterone production. Based on these observations, we investigated the interaction between the purinergic and nitrergic systems in Leydig cells of adult mice. For this purpose, we recorded ATP-evoked currents in isolated Leydig cells using the whole cell patch clamp technique after treatment with L-NAME (300 μM and 1 mM), L-arginine (10, 100, 300, and 500 μM), ODQ (300 μM), and 8-Br-cGMP (100 μM). Our results show that NO produced by Leydig cells in basal conditions is insufficient to change the ATP-evoked currents and that extra NO provided by adding 300 μM L-arginine positively modulates the current through a mechanism involving the NO/cGMP signaling pathway. Thus, we report an interaction between the nitrergic and purinergic systems in Leydig cells and suggest that Ca2+ entry via the purinergic receptors can be regulated by NO.

Monitoring Thiopurine Metabolites in Korean Pediatric Patients with Inflammatory Bowel Disease

PURPOSE: This study aimed to assess the role of thiopurine S-methyltransferase (TPMT) and 6-thioguanine nucleotide (6-TGN) as predictors of clinical response and side effects to azathioprine (AZA), and estimate the optimal AZA dose in Korean pediatric inflammatory bowel disease (IBD) patients. MATERIALS AND METHODS: One hundred and nine pediatric IBD patients in whom AZA treatment was required were enrolled. Thiopurine metabolites were monitored since September 2010. Among them, 83 patients who had prescribed AZA for at least 3 months prior to September 2010 were enrolled and followed until October 2011 to evaluate optimal AZA dose, adverse effects and disease activity before and after thiopurine metabolite monitoring. RESULTS: The result of the TPMT genotype was that 102 patients were *1/*1 (wild type), four were *1/*3C, one was *1/*6, one was *1/*16 (heterozygote) and one was *3C/*3C (homozygote). Adverse effects happened in 31 patients pre-metabolite monitoring and in only nine patients post-metabolite monitoring. AZA dose was 1.4+/-0.31 mg/kg/day before monitoring and 1.1+/-0.46 mg/kg/day after monitoring (p<0.001). However, there were no statistical differences in disease activity during metabolite monitoring period (p=0.34). Adverse effects noticeably decreased although reduction of the AZA dose since monitoring. CONCLUSION: TPMT genotype and thiopurine metabolite monitoring could be helpful to examine TPMT genotypes before administering AZA and to measure 6-TGN concentrations during prescribing AZA in IBD patients.