title: Baroreflex function in conscious rats submitted to iron overload.
abstract: Our hypothesis is that iron accumulated in tissue, rather than in serum, may compromise cardiovascular control. Male Fischer 344 rats weighing 180 to 220 g were divided into 2 groups. In the serum iron overload group (SIO, N = 12), 20 mg elemental iron was injected ip daily for 7 days. In the tissue iron overload group (TIO, N = 19), a smaller amount of elemental iron was injected (10 mg, daily) for 5 days followed by a resting period of 7 days. Reflex heart rate responses were elicited by iv injections of either phenylephrine (0.5 to 5.0 microg/kg) or sodium nitroprusside (1.0 to 10.0 microg/kg). Baroreflex curves were determined and fitted to sigmoidal equations and the baroreflex gain coefficient was evaluated. To evaluate the role of other than a direct effect of iron on tissue, acute treatment with the iron chelator deferoxamine (20 mg/kg, iv) was performed on the TIO group and the baroreflex was re-evaluated. At the end of the experiments, evaluation of iron levels in serum confirmed a pronounced overload for the SIO group (30-fold), in contrast to the TIO group (2-fold). Tissue levels of iron, however, were higher in the TIO group. The SIO protocol did not produce significant alterations in the baroreflex curve response, while the TIO protocol produced a nearly 2-fold increase in baroreflex gain (-4.34 +/- 0.74 and -7.93 +/- 1.08 bpm/mmHg, respectively). The TIO protocol animals treated with deferoxamine returned to sham levels of baroreflex gain (-3.7 +/- 0.3 sham vs -3.6 +/- 0.2 bpm/mmHg) 30 min after the injection. Our results indicate an effect of tissue iron overload on the enhancement of baroreflex sensitivity.
authors.affiliation: Departamento de Ciências Biológicas, NUPEB, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil. chianca@nupeb.ufop.br
authors.forename: L M
authors.initials: LM
authors.lastname: Cardoso
authors.forename: M L
authors.initials: ML
authors.lastname: Pedrosa
authors.forename: M E
authors.initials: ME
authors.lastname: Silva
authors.forename: M F D
authors.initials: MF
authors.lastname: Moraes
authors.forename: E
authors.initials: E
authors.lastname: Colombari
authors.forename: D A
authors.initials: DA
authors.lastname: Chianca
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D003243:Consciousness; D003676:Deferoxamine / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D007502:Iron Chelating Agents / Q000494:pharmacology*; D019190:Iron Overload / Q000503:physiopathology*; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D007502:Iron Chelating Agents; D009599:Nitroprusside; D003676:Deferoxamine