title: Cardiac function of two ecologically distinct Neotropical freshwater fish: Curimbata, Prochilodus lineatus (Teleostei, Prochilodontidae), and trahira, Hoplias malabaricus (Teleostei, Erythrinidae).
abstract: An isometric muscle preparation was used to investigate the importance of the ventricular sarcoplasmic reticulum (SR) and extracellular Ca(2+) (2.5 up to 10.5 mM) to force generation at 25 degrees C (acclimation temperature) in two ecologically distinct Neotropical teleost fish: Curimbata (active species), and trahira (sedentary species). The post-rest force was studied with and without 10 muM ryanodine in the medium. The positive inotropism observed for both species in response to increases on extracellular Ca(2+) reflected a greater Ca(2+) influx through sarcolemma, as well as an increase in Ca(2+) liberation from the SR by the Ca(2+)-induced Ca(2+) release mechanism. The significant post-rest potentiation recorded for the curimbata and trahira control preparations (3.22+/-0.24 to 6.55+/-0.77 mN mm(-2) and 0.74+/-0.07 to 2.26+/-0.26 mN mm(-2), respectively), was completely inhibited by the addition of ryanodine to the bathing medium, suggesting a potential functionality of SR for both species. Considering the differences in these species habitats, modes of life and levels of activity and the fact of a probable SR Ca(2+) cycling in a physiological temperature, we suggest that the functionality of the SR in these species is probably related to their phylogeny.
authors.affiliation: Department of Physiological Sciences, Federal University of São Carlos, Via Washington Luiz, Km 235, 13565-905, São Carlos, SP, Brazil.
authors.forename: Luciano
authors.initials: L
authors.lastname: Rivaroli
authors.forename: Francisco Tadeu
authors.initials: FT
authors.lastname: Rantin
authors.forename: Ana Lúcia
authors.initials: AL
authors.lastname: Kalinin
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002320:Cardiovascular Physiological Phenomena; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D006352:Heart Ventricles / Q000033:anatomy & histology; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009200:Myocardial Contraction; D012433:Ryanodine; D012519:Sarcoplasmic Reticulum / Q000502:physiology; D016276:Ventricular Function
chemical_list: D012433:Ryanodine; D002118:Calcium