Effects of temperature and calcium availability on cardiac contractility in Synbranchus marmoratus, a neotropical teleost.
An isometric muscle preparation was used to investigate the importance of the ventricular sarcoplasmic reticulum (SR) and extracellular Ca2+ (1.25 up to 11.25 mM) to force generation at 25 degrees C (acclimation temperature), 15 and 35 degrees C. The post-rest tension and force-frequency relationship were conducted with and without 10 microM ryanodine in the bathing medium. Increments in extracellular Ca2+ resulted in increases in twitch force development only at 35 degrees C. A significant post-rest potentiation was recorded for the control preparations at 25 degrees C (100% to 119.8+/-4.1%). However, this post-rest potentiation was inhibited by ryanodine only at 25 degrees C (100% to 97.6+/-1.5%). At 35 degrees C, force remained unchanged in the control preparations, but a significant post-rest decay was recorded in the presence of ryanodine (100% to 76.6+/-4.6%) while at 15 degrees C, ryanodine was not able to preventing the post-rest potentiation observed in the control preparations. The increases in the imposed contraction frequency caused a decline of the force at 25 and 35 degrees C and ryanodine decreased significantly peak tension at both temperatures. The findings suggest a high or medium calcium turnover, possibly related to the presence of a functional SR, whose functionality is diminished when temperature is decreased.
Rocha
Matheus Lavorenti
ML
Department of Physiological Science, Federal University of São Carlos, Via Washington Luiz, Km 235-13565-905, São Carlos, SP, Brazil.
Rantin
Francisco Tadeu
FT
Kalinin
Ana Lucia
AL
D000818:Animals; D001682:Biological Availability; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D023701:Smegmamorpha / Q000502:physiology*; D013696:Temperature
D012433:Ryanodine; D002118:Calcium