Nos3 Gene Knockout in Mice Enhances Kidney Sensitivity to Furosemide

Nitric oxide (NO) regulates renal hemodynamics and inhibits tubular sodium reabsorption. NO formation is catalyzed by NO synthases (NOS), and it is important to study the role of individual NO synthases for renal functions. The purpose of the study was to obtain a line of mice with a knockout of the nos3 gene (NOS KO) and to evaluate their ion-regulatory renal function. A homozygous line of NOS KO mice was developed at the background of the C57Bl/6 line using the CRISPR-Cas9 editing method. The physiological study included 39 animals (10 female and 10 male C57Bl/6 mice; 10 female and 9 male NOS KO mice); genotyping was carried out using PCR and sequencing methods at the age of 4 weeks. To identify differences in the transport of sodium and potassium in the kidneys of NOS KO mice, experiments were conducted to assess ion excretion in animals when given water (control), with a NaCl load (7.7 µmol/g) and with the administration of a loop diuretic. In the control, no differences were detected in the excretion of sodium and potassium ions in NOS KO and C57Bl/6 mice. Under conditions of excess NaCl intake, no significant interstrain differences were also revealed: sodium and potassium excretion increased by 8.8 and 1.3 times in NOS KO mice and by 8.4 and 1.7 times in wild-type mice, respectively. The natriuretic effect of furosemide (5 µg/g) in NOS KO mice was greater than in C57Bl/6 mice. Urinary sodium excretion was 4.1 ± 0.3 µmol/g during 2 hours of observation in NOS KO and 2.7 ± 0.2 µmol/g in wild-type mice (p < 0.001). Thus, the work revealed for the first time an increase in sensitivity to furosemide in mice with a knockout of the nos3 gene, which may indicate the importance of the activity of endothelial NO synthase for the regulation of sodium transport in the thick ascending limb of the loop of Henle.