Abstract 321: Phenotyping of NO-Insensitive Soluble Guanylate Cyclase beta1H105F Knockin Mice
Background Soluble Guanylate Cyclase (sGC) is a heterodimer, consisting of an alpha1- or alpha2-subunit and a beta1-subunit. Activation of sGC by NO/CO critically depends on the presence of a prosthetic ferrous heme group, linked to the axial ligand His-105 of the beta1-subunit. Removal of this heme moiety as well as its oxidation abolishes any NO-induced enzyme activation. To differentiate between sGC-dependent and sGC-independent functions of NO, and to differentiate between heme-dependent and heme-independent functions of sGC, we generated heme-deficient sGCbeta1H105F knockin (KI) mice, in which sGC retains its basal activity, but can no longer be activated by NO.
Methods. sGCbeta1H105F knockin mice were generated using a classical approach by which the sGCbeta1 allele was replaced with a mutated allele by means of homologous recombination. As such, the codon for the His-105 residue of the sGCbeta1-subunit was replaced by a codon for Phe. Blood pressure was measured using tail-cuff and telemetry methods. Aorta relaxation was measure in organ baths.
Results. sGCbeta1H105F knockin mice showed a reduced life span, gastro-intestinal tract abnormalities, and growth retardation. Basal SBP was higher in sGCbeta1H105F knockin mice than in WT mice (142 ±15 vs. 113 ±8 mm Hg, P< 0.01). The acute response in BP to NO-donors (DETA-NO, SNP) and L-NAME was abolished. Relaxation of precontracted aortic and femoral rings in response to acetylcholine and sodium nitroprusside was impaired. Circadian rhythms in blood pressure were disturbed.
Conclusion. Soluble guanylate cyclase is an important regulator of blood pressure and arterial relaxation. Effects of NO donor compounds seem to be critically dependent on sGC.