Time dependent regulation of nitric oxide synthase (NOS) isoforms mRNA expression in early and established streptozotocin diabetes

Abstract

Inhibition of all NOS isoforms, or only NOS1, augments renal autoregulation in normal mammals. Recently, non-selective NOS inhibition was reported to profoundly affect autoregulation after 1 week of diabetes (DM) (AJP 295: F445, 2008) but not after 4 weeks of DM (AJP 296: R1761, 2009). To address this apparent contradiction, we tested the gene expression of the NOS isoforms in renal cortex after 1 and 4 weeks of DM. Adult, male Long-Evans rats were given streptozotocin (60mg/kg IV), then insulin implants to keep blood glucose ~24mmol/L. Kidneys were harvested and mRNA was quantified by real time RT-PCR. Nos1 expression, relative to contemporaneous untreated controls, was 3.3 (range 2.5–4.3)-fold after 1 week and 0.27 (0.20–0.35)-fold after 4 weeks, while Nos 2 was 0.45 (0.31–0.66)-fold then 2.08 (1.52–2.85)-fold and Nos3 was 1.71 (1.41–2.08)-fold then 0.29 (0.23–0.37)-fold. Nos1 gene expression was consistent with previous functional data, while Nos3 expression was not. Very little Nos2 mRNA was present in any rat at either time. This suggests that Nos1 is the most important with respect to autoregulation in DM. Funded by Victoria Fdn, CIHR and UVic SURA.