CONICET | Buscador de Institutos y Recursos Humanos

Nitric oxide synthases (NOS) are involved in many aspects of cardiovascular homeostasis including regulation of blood pressure and heart rate (HR). Objectives: (i) to investigate the role of NO pathway in the cardiovascular adjustment in hemorrhaged rats (bleeding: 20% of the volemia) (ii) to study a relationship between caveolin-1 and NOS in this experimental model. Methods: Groups of animals (n=10/age group): S= sham, H= hemorrhaged rats, S+L-NAME (1 mg/kg iv and 0.5 mg/kg.h iv = 100l/h), H+L-NAME. We evaluated in the left ventricle the NOS activity (NADPH-d technique), eNOS expression (Western blot) and coimmunoprecipitation analysis of caveolin-1 and eNOS (Immunofluorescence) at 60 and 120 min of bleeding. Analysis of variance (ANOVA) followed by the ad hoc Bonferroni test was used for multiple comparisons. The 5% probability level was used as a criterion for biological significance. Results: L-NAME restored the hypotension induced by hemorrhage. Blood loss decreased heart rate in the first stage increasing at 60 and 120 min. L-NAME blunted this effect. Left ventricle histochemical NOS activity increased at 60 and 120 min (21% and 45%, respectively). eNOS protein levels increased in left ventricle at 60 min without changes at 120 min compared with S group. eNOS exhibited a diffuse staining pattern throughout the ventricle cell and is significantly associated with caveolin-1 in S group. Meanwhile, at 60 min of bleeding a dissociation of caveolin-1 and eNOS was observed. The binding of caveolin-1 with eNOS is partially restored at 120 min. Conclusions: The involvement of NO pathway on cardiovascular parameters occurs in an isoform-specific and time dependent manner after blood loss. This response would be influenced by direct protein interactions between the eNOS and it regulatory protein, caveolin-1 in hemorraghed rat.