Differential nNOS gene expression in salt-sensitive and salt-resistant Dahl rats

Background Several indications exist to suggest that an impaired production of nitric oxide might have a role in the development of salt-sensitive hyp ertension. Objective To examine whether the gene expression of the nitric oxide syntha ses (NOS) is altered in the salt-sensitive Dahl rat compared with that in t he salt-resistant Dahl rat. Design and methods The abundance of NOS mRNA was measured by RNase protecti on assay in different organs of salt-resistant and salt-sensitive Dahl rats . In addition, the zonal expression of NOS genes in the kidney under salt l oad and salt restriction was determined. Results The abundance of endothelial NOS mRNA was similar between the salt- resistant and salt-sensitive Dahl rat strains in all organs. Inducible NOS mRNA was not detectable by RNase protection assay in any organ. Neuronal NO S (nNOS) mRNA expression, however, was about 50% lower in brain and kidney of salt-sensitive Dahl rats than in salt-resistant Dahl rats. Within the ki dney, nNOS mRNA levels were significantly decreased in salt-sensitive Dahl rats compared with those in salt-resistant Dahl rats, in cortex, outer and inner medulla (50, 40 and 30%, respectively) under all dietary conditions. A comparison of renal nNOS gene expression in Dahl rats with that in salt-i nsensitive Sprague-Dawley rats revealed that the abundance of renal nNOS wa s similar in salt-sensitive Dahl and Sprague-Dawley rats, but was increased in salt-resistant Dahl rats relative to that in Sprague-Dawley rats. Conclusion These data suggest that nNOS gene expression is increased in sal t-resistant Dahl rats compared with that in salt-sensitive Dahl rats. This increased nNOS expression of the salt-resistant Dahl strain might play a pa rt in compensating for a defect of renal salt excretion in the Dahl strains . (C) 2001 Lippincott Williams & Wilkins.