Impact of the NO-Sensitive Guanylyl Cyclase 1 and 2 on Renal Blood Flow and Systemic Blood Pressure in Mice

Abstract

Nitric oxide (NO) modulates renal blood flow (RBF) and kidney function and is involved in blood pressure (BP) regulation predominantly via stimulation of the NO-sensitive guanylyl cyclase (NO-GC), existing in two isoforms, NO-GC1 and NO-GC2. Here, we used isoform-specific knockout (KO) mice and investigated their contribution to renal hemodynamics under normotensive and angiotensin II-induced hypertensive conditions. Stimulation of the NO-GCs by S-nitrosoglutathione (GSNO) reduced BP in normotensive and hypertensive wildtype (WT) and NO-GC2-KO mice more efficiently than in NO-GC1-KO. NO-induced increase of RBF in normotensive mice did not differ between the genotypes, but the respective increase under hypertensive conditions was impaired in NO-GC1-KO. Similarly, inhibition of endogenous NO increased BP and reduced RBF to a lesser extent in NO-GC1-KO than in NO-GC2-KO. These findings indicate NO-GC1 as a target of NO to normalize RBF in hypertension. As these effects were not completely abolished in NO-GC1-KO and renal cyclic guanosine monophosphate (cGMP) levels were decreased in both NO-GC1-KO and NO-GC2-KO, the results suggest an additional contribution of NO-GC2. Hence, NO-GC1 plays a predominant role in the regulation of BP and RBF, especially in hypertension. However, renal NO-GC2 appears to compensate the loss of NO-GC1, and is able to regulate renal hemodynamics under physiological conditions.

Keywords: L-NAME; NO-GC; NO-sensitive guanylyl cyclase; blood pressure; cGMP; hypertension; kidney; nitric oxide; renal blood flow; vasorelaxation.

Figure 1

Increased blood pressure but normal renal blood flow in anesthetized NO-sensitive guanylyl cyclase1 knockout (NO-GC1-KO) and NO-GC2-KO mice. (A) Blood pressure was significantly increased in NO-GC1-KO (n = 16) and NO-GC2-KO (n = 17) compared to WT (n = 54) mice; (B) Renal blood flow was not different in unconscious WT (n = 33), NO-GC1-KO (n = 16) and NO-GC2-KO (n = 16) mice. Data represent means ± standard error of the mean (SEM); * p < 0.05 vs. wildtype (WT). One-way standard error of the mean (ANOVA) followed by Bonferroni’s multiple comparison post hoc test.

Figure 2

Predominant role of NO-GC1 in GSNO-induced blood pressure reduction and renal blood flow increase in anesthetized mice. (A,B) In normotensive mice, GSNO induced blood pressure reduction, expressed as absolute blood pressure values and blood pressure reduction, was attenuated in NO-GC1-KO (n = 3) compared to WT (n = 8) and NO-GC2-KO (n = 5) mice; (C) In normotensive mice, GSNO-induced increase in renal blood flow did not differ between the three genotypes (n = 3–8); (D–F) In Ang II-infused mice (200 ng/kg/min), GSNO-induced blood pressure reduction, expressed as absolute blood pressure values and blood pressure reduction, and renal blood flow increase were significantly attenuated in NO-GC1-KO (n = 3) compared to WT (n = 5) and NO-GC2-KO (n = 4) mice. * p < 0.05, ** p < 0.01, *** p < 0.001 vs. NO-GC1-KO; # p < 0.01, ## p < 0.001 vs. NO-GC2-KO. Two-way ANOVA followed by Bonferroni’s multiple comparison post hoc test.

Figure 3

Inhibition of NO production by L-NAME affects blood pressure and renal blood flow in NO-GC1-KO and NO-GC2-KO mice. (A) In anesthetized mice, administration of L-NAME increased blood pressure to the same level; (B) L-NAME-induced blood pressure increase was significantly attenuated in NO-GC1-KO (n = 5) and NO-GC2-KO (n = 7) compared to WT (n = 9) mice; (C) Renal blood flow was significantly decreased by L-NAME in WT (n = 7), NO-GC1 (n = 4) and NO-GC2-KO (n = 6) mice; (D) L-NAME-induced reduction in renal blood flow was significantly reduced in NO-GC1-KO compared to NO-GC2-KO mice (n = 4–7). * p < 0.05; # p < 0.01 vs. NO-GC2-KO. One-way ANOVA or two-way ANOVA followed by Bonferroni’s multiple comparison post hoc test.

Figure 4

Impaired NO-mediated renal vasorelaxation in NO-GC1-KO and NO-GC2-KO mice. (A) Endothelial-dependent renal vasorelaxation by carbachol (30 µM) was significantly reduced in isolated perfused kidneys of NO-GC1-KO compared to WT mice; (B) Smooth muscle cell-dependent vasorelaxation induced by the NO donor GSNO was significantly attenuated in isolated perfused kidneys of NO-GC1-KO (n = 8) and NO-GC2-KO (n = 13) compared to WT (n = 11) mice; (C) Atrial natriuretic peptide (ANP)-induced renal vasorelaxation did not differ between WT (n = 6), NO-GC1-KO (n = 10) and NO-GC2-KO (n = 5) mice; (D) Renal NO-GC activity was significantly decreased in NO-GC1-KO (n = 6) compared to WT (n = 19) and NO-GC2-KO (n = 7) mice; (E) Renal cGMP levels at baseline, in response to carbachol (30 µM) or DEA-NO (100 µM) were significantly decreased in NO-GC1-KO (10 slices of n = 3) and NO-GC2-KO (11 slices of n = 3) compared to WT (10 slices of n = 3) mice. * p < 0.05, ** p < 0.01, *** p < 0.001 vs. WT; # p < 0.05, ## p < 0.01 vs. NO-GC1-KO-mice. Two-way ANOVA followed by Bonferroni’s multiple comparison post hoc test or one-way ANOVA followed by Bonferroni’s multiple comparison post hoc test.

Figure 5

Predominant role of NO-GC1 in NO-mediated blood pressure changes in conscious mice. (A) Blood pressure reduction induced by the NO donor sodium nitroprusside (SNP) (30 µg/kg BW) was significantly diminished in conscious NO-GC1-KO (n = 4) mice compared to WT (n = 4) and NO-GC2-KO (n = 4) mice measured by radio telemetry; (B) Attenuated blood pressure increase by L-NAME (30 mg/kg BW) in NO-GC1-KO mice compared to WT and NO-GC2-KO mice; (C,D) Co-administration of hexamethonium (30 mg/kg BW) enhanced blood pressure reduction by GSNO and blood pressure increase by L-NAME in NO-GC1-KO (n = 6) compared to WT (n = 6) and NO-GC2-KO (n = 6) mice. * p < 0.05, ** p < 0.01, *** p < 0.001 vs. WT; # p < 0.05, ## p < 0.01, ### p < 0.001 vs. NO-GC2-KO-mice. Two-way ANOVA followed by Bonferroni’s multiple comparison post hoc test.

Figure 5

Predominant role of NO-GC1 in NO-mediated blood pressure changes in conscious mice. (A) Blood pressure reduction induced by the NO donor sodium nitroprusside (SNP) (30 µg/kg BW) was significantly diminished in conscious NO-GC1-KO (n = 4) mice compared to WT (n = 4) and NO-GC2-KO (n = 4) mice measured by radio telemetry; (B) Attenuated blood pressure increase by L-NAME (30 mg/kg BW) in NO-GC1-KO mice compared to WT and NO-GC2-KO mice; (C,D) Co-administration of hexamethonium (30 mg/kg BW) enhanced blood pressure reduction by GSNO and blood pressure increase by L-NAME in NO-GC1-KO (n = 6) compared to WT (n = 6) and NO-GC2-KO (n = 6) mice. * p < 0.05, ** p < 0.01, *** p < 0.001 vs. WT; # p < 0.05, ## p < 0.01, ### p < 0.001 vs. NO-GC2-KO-mice. Two-way ANOVA followed by Bonferroni’s multiple comparison post hoc test.