title: Cardiovascular and electrocardiographic parameters after tonin administration in Wistar rats.
abstract: In order to understand the mechanisms of interaction between tonin-angiotensin and renin-angiotensin systems (RAS) we evaluated, "in vivo" and "in vitro", in Wistar rats, cardiovascular and electrocardiographic parameters after tonin administration. Arterial pressure (AP) and electrocardiogram (ECG) were recorded in awake animals before and after tonin administration. Langendorff technique was used to analyze cardiac function in isolated heart in the presence of tonin and video motion edge detection system was used to evaluate the effect of tonin upon contractile function of isolated rat ventricular cardiomyocytes. After tonin infusion rats presented significantly higher diastolic and mean arterial pressure (MAP) and heart rate (HR) as compared with control. The ECG analysis revealed shorter RR interval, increase in the low-frequency (LF) range of the heart rate variability (HRV) power (%) and decrease in the high-frequency (HF) of HRV power (%). Isolated hearts perfused with tonin presented an increase in the arterial coronary pressure (ACP) and decline in the ventricular systolic tension (ST), maximal (dT/dt+) and minimal (dT/dt) contractility. The rates of contraction and relaxation of isolated ventricular cardiomyocytes were significantly increased due to the presence of tonin. The angiotensin II (Ang II) levels in the coronary sinus effluent increased in the presence of tonin in a dose-dependent manner and the effect of tonin upon ACP was completely blocked by candesartan. Tonin is able to generate the vasoconstrictor peptide Ang II in the isolated heart of the rat and the cardiovascular response induced by tonin was completely blocked by candesartan, an indication that the action of Ang II on Ang II type 1 (AT1) receptors is the major mechanism of the heart effects. Tonin affects cardiomyocyte contractile function which may be due to interference with Ca(2+) handling.
authors: Department of Educational Development, Federal Institute of Education, Science and Technology of Southeast Minas Gerais, Campus Barbacena, MG, Brazil. denis.damasceno@ifsudestemg.edu.br
authors: Denis D
authors: DD
authors: Damasceno
authors: Mercia P
authors: MP
authors: Lima
authors: Daisy F
authors: DF
authors: Motta
authors: Anderson J
authors: AJ
authors: Ferreira
authors: Judson F
authors: JF
authors: Quintão-Junior
authors: Lucas R
authors: LR
authors: Drummond
authors: Antônio J
authors: AJ
authors: Natali
authors: Alvair P
authors: AP
authors: Almeida
authors: Jorge L
authors: JL
authors: Pesquero
mesh_terms: D000804:Angiotensin II / Q000819:agonists / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D062186:Arterial Pressure / Q000187:drug effects; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1 / Q000819:agonists / Q000378:metabolism*; D012084:Renin-Angiotensin System / Q000187:drug effects*; D013777:Tetrazoles / Q000494:pharmacology; D020840:Tissue Kallikreins / Q000494:pharmacology*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D000804:Angiotensin II; C117017:tonin; D020840:Tissue Kallikreins; C081643:candesartan; D002118:Calcium