title: Reduced Activity of the Aortic Gamma-Glutamyltransferase Does Not DecreaseS-Nitrosoglutathione Induced Vasorelaxation of Rat Aortic Rings.
abstract: Aims:Gamma-glutamyl transferase (GGT), an enzyme present on the endothelium, is involved in the release of nitric oxide (NO) fromS-nitrosoglutathione (GSNO) and in the GSNO-induced vasodilation. Endogenous GSNO is a physiological storage form of NO in tissues while exogenous GSNO is an interesting candidate for compensating for the decreased NO bioavailability occurring during cardiovascular diseases. We investigated in a rat model of human hypertension, the spontaneous hypertensive rat (SHR), submitted or not to high salt diet, whether a decreased vascular GGT activity modifies the vasorelaxant effect of GSNO.Methods:Thoracic aortic rings isolated from male SHR and Wistar Kyoto rats (WKY) aged 20-22 weeks-submitted or not for 8 weeks to a high salt diet (1% w/v NaCl in drinking water) were pre-constricted with phenylephrine then submitted to concentration-vasorelaxant response curves (maximal response: Emax; pD2) to carbachol or sodium nitroprusside to evaluate endothelial dependent or independent NO-induced vasodilation, or GSNO (exogenous NO vasodilation depending from the endothelial GGT activity). GGT activity was measured using a chromogenic substrate in aortic homogenates. Its role in GSNO-induced relaxation was assessed following inhibition of the enzyme activity (serine-borate complex). That of protein disulfide isomerase (PDI), another redox sensitive enzyme involved in GSNO metabolism, was assessed following inhibition with bacitracin.Results:Aortic GGT activity (18-23 μmol/min/mg of tissue in adult WKY) decreased by 33% in SHR and 45% in SHR with high salt diet. Emaxand pD2for sodium nitroprusside were similar in all groups. Emaxfor carbachol decreased by -14%, reflecting slight endothelial NO-dependent dysfunction. The GSNO curve was slightly shifted to the left in SHR and in SHR with high salt diet, showing a small enhanced sensitivity to GSNO. Involvements of GGT, as that of PDI, in the GSNO effects were similar in all groups (pD2for GSNO -0.5 to -1.5 following enzymatic inhibition).Conclusion:Hypertension is associated with a decreased aortic GGT activity without decreasing the vasorelaxant effects of GSNO, whose bioactivity may be supplemented through the alternative enzymatic activity of PDI.
authors.affiliation: EA3452 CITHEFOR "Drug Targets, Formulation and Preclinical Assessment", Faculté de Pharmacie, Université de Lorraine Nancy, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Perrin-Sarrado
authors.affiliation: EA3452 CITHEFOR "Drug Targets, Formulation and Preclinical Assessment", Faculté de Pharmacie, Université de Lorraine Nancy, France.
authors.forename: Marios
authors.initials: M
authors.lastname: Pongas
authors.affiliation: EA3452 CITHEFOR "Drug Targets, Formulation and Preclinical Assessment", Faculté de Pharmacie, Université de Lorraine Nancy, France.
authors.forename: Fatima
authors.initials: F
authors.lastname: Dahboul
authors.affiliation: EA3452 CITHEFOR "Drug Targets, Formulation and Preclinical Assessment", Faculté de Pharmacie, Université de Lorraine Nancy, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Leroy
authors.affiliation: Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa Medical School Pisa, Italy.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Pompella
authors.affiliation: EA3452 CITHEFOR "Drug Targets, Formulation and Preclinical Assessment", Faculté de Pharmacie, Université de Lorraine Nancy, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Lartaud
keywords: NO-dependent vasorelaxation; S-nitrosoglutathione; Spontaneous Hypertensive Rat; aortic ring; gamma-glutamyltransferase