title: Changes in cardiovascular responses to chemoreflex activation of rats recovered from protein restriction are not related to AT1receptors.
abstract: What is the central question of this study? In this study, we sought to investigate whether cardiovascular responses to peripheral chemoreflex activation of rats recovered from protein restriction are related to activation of AT1receptors. What is the main finding and its importance? This study highlights the fact that angiotensinergic mechanisms activated by AT1receptors do not support increased responses to peripheral chemoreflex activation by KCN in rats recovered from protein restriction. Also, we found that protein restriction led to increased resting ventilation in adult rats, even after recovery. The effects of a low-protein diet followed by recovery on cardiorespiratory responses to peripheral chemoreflex activation were tested before and after systemic angiotensin II type 1 (AT1) receptor antagonism. Male Fischer rats were divided into control and recovered (R-PR) groups after weaning. The R-PR rats were fed a low-protein (8%) diet for 35 days and recovered with a normal protein (20%) diet for 70 days. Control rats received a normal protein diet for 105 days (CG105). After cannulation surgery, mean arterial pressure, heart rate, respiratory frequency, tidal volume and minute ventilation were acquired using a digital recording system in freely moving rats. The role of angintensin II was evaluated by systemic antagonism of AT1receptors with losartan (20 mg kg-1i.v.). The peripheral chemoreflex was elicited by increasing doses of KCN (20-160 μg kg min-1, i.v.). At baseline, R-PR rats presented increased heart rate and minute ventilation (372 ± 34 beats min-1and 1.274 ± 377 ml kg-1min-1) compared with CG105animals (332 ± 22 beats min-1and 856 ± 112 ml kg-1min-1). Mean arterial pressure was not different between the groups. Pressor and bradycardic responses evoked by KCN (60 μg kg-1) were increased in R-PR (+45 ± 13 mmHg and -77 ± 47 beats min-1) compared with CG105rats (+25 ± 17 mmHg and -27 ± 28 beats min-1), but no difference was found in the tachypnoeic response. These differences were preserved after losartan. The data suggest that angiotensin II acting on AT1receptors may not be associated with the increased heart rate, increased minute ventilation and acute cardiovascular responses to peripheral chemoreflex activation in rats that underwent postweaning protein restriction followed by recovery.
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Renato Willian Martins
authors.identifier: 0000-0001-9023-2777
authors.initials: RW
authors.lastname: Sá
authors.affiliation: Department of Physiology and Biophysics, ICB, Federal University of Minas Gerais, 31, 270-910, Belo Horizonte, MG, Brazil.
authors.forename: Andrea Siqueira
authors.initials: AS
authors.lastname: Haibara
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Paula Magalhães
authors.initials: PM
authors.lastname: Gomes
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Giovana Lopes
authors.initials: GL
authors.lastname: Aguiar
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Rafael Souza Leopoldino
authors.initials: RS
authors.lastname: Nascimento
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Maria Lucia
authors.initials: ML
authors.lastname: Pedrosa
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Andréia Carvalho
authors.initials: AC
authors.lastname: Alzamora
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Lisandra Brandino
authors.initials: LB
authors.lastname: de Oliveira
authors.affiliation: Department of Biological Sciences, ICEB/NUPEB, Federal University of Ouro Preto - Campus Universitário Morro do Cruzeiro, 35, 400-000, Ouro Preto, MG, Brazil.
authors.forename: Leonardo Máximo
authors.initials: LM
authors.lastname: Cardoso
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D062186:Arterial Pressure / Q000187:drug effects / Q000502:physiology; D001919:Bradycardia / Q000378:metabolism; D002319:Cardiovascular System / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology*; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D018753:Diet, Protein-Restricted / Q000379:methods; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D019808:Losartan / Q000494:pharmacology; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D013610:Tachycardia / Q000378:metabolism; D013990:Tidal Volume / Q000187:drug effects / Q000502:physiology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D019808:Losartan
keywords: angiotensin II; chemoreflex; malnutrition; recovery; respiratory control