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 µg/kg) or sodium nitroprusside (1.0 to 10.0 µg/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 reevaluated. 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.

1.8 cineole decreases gastric compliance in anesthetized rats

“…For this proposite, we use a data acquisition system (PowerLab-ADInstruments®), considered standard for literature. Basal results of AP are similar to gotten for others 6 . 1,8 cineoleee presente an hipotensor effect, AP returned to basal levels to soon after 10min of the treatment, similar to observed for others 7,8,9 .…”

Nitric Oxide Reduces Vagal Baroreflex Sensitivity in the Late Gestation Fetus

“…In addition, it has been reported that SNP has nonspecific pharmacological effects, for instance by promoting the release of iron and cyanide (35) and that iron overload can enhance baroreflex sensitivity (36). However, in the present study, withdrawal of the SNP infusion at the end of the experimental protocols led to a significant increase in fetal ABP and PI.…”

“…daily for 7 d followed by baroreflex evaluation) versus tissue iron overload (10 mg iron i.p. daily for 5 d followed by a resting period of 7 d and baroreflex evaluation) reported that baroreflex gain was only increased with tissue rather than serum iron overload (36). Since the entire experiment with the NO clamp in the present study lasted no more than 3 h, it is also unlikely that the increase in fetal cardiac baroreflex sensitivity during NOS blockade is due to the nonspecific pharmacological effects of SNP.…”

Increased α1-adrenoreceptor activity is required to sustain blood pressure in female rats under food restriction

“…where ΔmaxMAP is the maximal change in MAP after injection of sodium nitroprusside and ΔmaxHR is the maximal change in HR due to the changes in MAP caused by the pharmacological manoeuvre [7].…”