Age dependent expression and distribution of nitric oxide (NO) synthase isoforms in the ovine kidney

The aim of the present study was to measure intrarenal spatial and temporal localization of all three nitric oxide synthase (NOS) isoforms in the developing ovine kidney. Reverse transcriptase-polymerase chain reaction (RT-PCR), Western Blot analyses, and in situ hybridization techniques were performed for NOS I III isoforms in renal tissue obtained from sheep aged ~24 h, one, three, six, and 12 weeks post natally (N = 3). RT-PCR performed on cortical and medullary kidney tissue revealed the presence of all three NOS isoforms from day one to 12 weeks postnatally. NOS I and NOS II mRNA levels were greater in cortex compared to medulla during the first three weeks whereas NOS III mRNA levels were predominantly transcribed within the medulla. In all NOS isoforms, there was a decrease in cortical mRNA levels after three to six weeks. Protein levels confirmed the presence of all three NOS isoforms over the first three months of postnatal life. By demonstrating NOS isoform transcripts to be more abundant in the early post natal period, these findings may provide insight into the age dependent role of NO in modulating kidney function during ontogeny.