Subchronic exposure to nonylphenol ethoxylate (NPE) induces cardiotoxicity and oxidative stress in American bullfrog tadpoles: a mechanistic approach.

Tropical regions, particularly those with high levels of endemism such as South America, harbor a diverse array of amphibian species. However, these regions often lack specific regulations governing the release of emerging contaminants, including the surfactant nonylphenol ethoxylate (NPE), into water bodies, which can have devastating consequences for these sensitive ecosystems. This study evaluated the sublethal effects of 16-day subchronic exposure to NPE at an environmentally relevant concentration of 30 µg/L on American bullfrog (Lithobates catesbeianus) tadpoles using multiple endpoints, including biometric parameters, antioxidant responses, oxidative stress biomarkers, heart rate, and myocardial contractility.

Activation of the cannabinoid type 2 (CB2) receptor improves cardiac contractile performance in fish, Brycon amazonicus.

In addition to their well-known classical effects, cannabinoid CB1 and CB2 receptors have also been involvement in both deleterious and protective actions on the heart under various pathological conditions. While the potential therapeutic applications of the endocannabinoid system in the context of cardiovascular function are indeed a viable prospect, significant debate exists within the literature regarding whether CB1, CB2, or a combination of both receptors exert a favorable influence on cardiac function. Hence, the aim of this study was to investigate the effects of CB1 + CB2 or CB2 agonists on cardiac excitation-contraction (E-C) coupling, utilizing fish (Brycon amazonicus) as an experimental model.

Tolerance of an acute warming challenge declines with body mass in Nile tilapia: evidence of a link to capacity for oxygen uptake.

It has been proposed that larger individuals within fish species may be more sensitive to global warming, as a result of limitations in their capacity to provide oxygen for aerobic metabolic activities. This could affect size distributions of populations in a warmer world but evidence is lacking. In Nile tilapia Oreochromis niloticus (n=18, mass range 21-313 g), capacity to provide oxygen for aerobic activities (aerobic scope) was independent of mass at an acclimation temperature of 26°C.

Hormetic-like dose-response induced by alternagin-C, a protein isolated from urutu snake (Rhinocerophis alternatus) venom, in fish (Hoplias malabaricus) cardiac contractility.

The aim of this study was to evaluate the effects of different doses of alternagin-C, a disintegrin-like protein from Rhinocerophis alternatus venom, on myocardial contractility of the freshwater fish Hoplias malabaricus, an alternative model to contractile function studies. Alternagin-C treatment exhibited a hormetic-like dose-response curve with a strong positive inotropism and enhanced cardiac pumping capacity at low dose, whereas a modest inotropism and a left shift in the force-frequency relationship was registered at high dose.

Cardiac contractility of the African sharptooth catfish, Clarias gariepinus: role of extracellular Ca, sarcoplasmic reticulum, and β-adrenergic stimulation.

This study investigated the dependence of contraction from extracellular Ca, the presence of a functional sarcoplasmic reticulum (SR), and the effects of β-adrenergic stimulation using isometric cardiac muscle preparations. Moreover, the expression of Ca-handling proteins such as SR-Ca-ATPase (SERCA), phospholamban (PLN), and Na/Ca exchanger (NCX) were also evaluated in the ventricular tissue of adult African sharptooth catfish, Clarias gariepinus, a facultative air-breathing fish. In summary, we observed that (1) contractility was strongly regulated by extracellular Ca; (2) inhibition of SR Ca-release by application of ryanodine reduced steady-state force production; (3) ventricular myocardium exhibited clear post-rest decay, even in the presence of ryanodine, indicating a decrease in SR Ca content and NCX as the main pathway for Ca extrusion; (4) a positive force-frequency relationship was observed above 60 bpm (1.