Efeitos da temperatura e manejo do cálcio sobre o miocárdio ventricular do teleosteo neotropical Prochilodus lineatus.

AUTOR(ES)

Telma Aparecida Costa

DATA DE PUBLICAÇÃO

2005

RESUMO

The present study anlyzed the in vivo and in vitro responses of the myocardium obtained from Prochilodus lineatus acclimated at 25 C and tested at 25 and 35 C. The in vivo heart rate (fH bpm) was measured during acute transitions in temperature and subsequent return to 25 C. ECG recordings (lead DI of the electrocardiography) were obtained of electrodes at cardiac region. Recordings of the isometric contraction force (Fc %) and time-dependent parameters (TPT time to peak tension; THR time to half relaxation) were obtainded in vitro from ventricle rings electrically paced in response to stimulation frequency, temperature, extracelular Ca2+, adrenaline and ryanodine (blocker of the sarcoplasmic reticulum SR). The species showed a significant increase in the fH during the transition from 25 to 35 C, showing the importance of the chronotropic adjustments in response to thermal alterations and a great tolerance and adaptation to different thermal conditions. The species did show significant decreases in the twitch force (Fc) development by the ventricular strips during the increases of temperature. The addition of crescent Ca2+ concentrations to the medium evidenced the importance of the extracellular Ca2+ as showed by the Fc increases at both 25 and 35 C. Concomitant increases in in TPT and THR here recorded at 25 C while at 35 C, such increases were observed only in TPT. Adrenaline caused positive inotropism only at 35 C, without effect on time-dependent parameters. The post rest tension was conducted with and without 10 M ryanodine in the medium. A significant post rest potentiation was recorded for at 25 and 35o C These post rest potentiations were inhibited by ryanodine. The impact of increases in the imposed contraction frequency caused a decline of the force and an increase in resting tension (RT) at both temperatures. In conclusion, an important fraction of the activator Ca2+ in P. lineatus seems to derive from intracellular stores (RS). However, this species also depends on extracellular sources of Ca2+, which provide more flexibility to modulate the contraction force.

ASSUNTO(S)

curimbatá (peixe) fisiologia de orgaos e sistemas fisiologia comparada acoplamento e-c eletrocardiograma miocárdio ventricular temperatura

Documentos Relacionados

• Efeitos morfológicos e fisiológicos da exposição aguda ao chumbo na espécie de peixe neotropical Prochilodus lineatus
• Efeito da exposição à atrazina nas brânquias de curimbatá, Prochilodus lineatus (Teleósteo, Prochilodontidae)
• Biomarcadores bioquímicos e genéticos para a detecção dos efeitos do herbicida Atrazina no peixe neotropical Prochilodus lineatus
• Efeitos dos herbicidas clomazone e ametrina em parâmetros funcionais da espécie de peixe neotropical Prochilodus lineatus
• Cultivo em piscicultura e seus efeitos sobre a morfologia de Prochilodus lineatus (Actinopterygii: Prochilodontidae)