Antônio Cláudio Mendes Ribeiro

Publications (2)2.58 Total impact

• Article: Characterization of the L-arginine-NO-cGMP pathway in spontaneously hypertensive rat platelets: the effects of pregnancy.

  Dayane Teixeira Ognibene, Monique Bandeira Moss, Cristiane Matsuura, Tatiana M Brunini, Roberto Soares de Moura, Antônio Cláudio Mendes-Ribeiro, Angela de Castro Resende
  [show abstract] [hide abstract]
  ABSTRACT: Nitric oxide (NO) is a short-lived intercellular messenger that provides an efficient vascular regulatory mechanism to support homeostasis and prevent thrombosis. Endothelial dysfunction and reduced NO bioavailability have a central role in hypertension associated with pregnancy. The purpose of this study was to investigate the impact of pregnancy on the L-arginine-NO-cGMP pathway in platelets and its correlation to platelet function and blood pressure in normotensive rats and spontaneously hypertensive rats (SHRs). Platelets were obtained from blood on the 20th day of pregnancy from female SHRs (SHR-P) and normotensive controls (P) or age-matched nonpregnant rats (SHR-NP and NP). Intraplatelet NO synthase (NOS) activity was reduced in P compared to NP, despite unchanged L-arginine influx. The expression levels of endothelial NOS (eNOS) and inducible NOS (iNOS) were diminished during pregnancy in normotensive rats. Paradoxically, cyclic guanosine monophosphate (cGMP) levels were similar between NP and P, as were phosphodiesterase type 5 (PDE5) expression and platelet aggregation induced by adenosine diphosphate. In SHRs, L-arginine influx was reduced in SHR-P compared to SHR-NP. SHR-P exhibited impaired NOS activity and reduced iNOS expression compared with SHR-NP. Soluble guanylyl cyclase and PDE5 expression in platelets were lower in SHR-P than in SHR-NP, whereas no differences were noted between groups with respect to cGMP levels. However, increased levels of cGMP were observed in SHR-P compared to normotensive groups and platelet aggregability remained unaltered. In conclusion, these observations prompted the hypothesis that normal platelet aggregation in pregnant SHRs may be related to a reduction in PDE5 expression and consequently the maintenance of cGMP levels, independently of reduced platelet NO bioavailability.
  Hypertension Research 09/2010; 33(9):899-904. · 2.58 Impact Factor
• Article: L-Arginine transport in disease.

  Antônio Cláudio Mendes Ribeiro, Tatiana M C Brunini
  [show abstract] [hide abstract]
  ABSTRACT: The importance of membrane transport in normal physiological cell function is unquestionable. However, to what extent alterations in the transport of amino acids are the cause and/or consequence of pathological changes observed in disease states is a question not yet completely clarified. Kinetic experiments with blood cells provide a simple and useful model for researching alterations in amino acid transport. The cationic amino acid L-arginine is the precursor of nitric oxide (NO), a key second messenger involved in functions such as endothelium-dependent vascular relaxation, immune defence and platelet activation. The transport of L-arginine, being rate-limiting for nitric oxide production, is extremely relevant to pathological conditions where NO synthesis and/or actions are affected. The current review provides an overview of L-arginine transport in disease, specifically in uraemia, heart failure, hypertension, diabetes mellitus, septic shock and sickle cell disease.
  Current Medicinal Chemistry - Cardiovascular & Hematological Agents 05/2004; 2(2):123-31.