Electrophysiological characteristics of freshly isolated ventricular myocytes from Zebrafish (Danio rerio)

Abstract

The Zebrafish (ZF) is a tropical fish that has been the focus of an increasing number of developmental studies. However, our understanding of the basic physiology of ZF, in particular cardiac excitation‐contraction coupling is limited. Indeed, there is currently no information about the electrical activity of single myocytes freshly isolated from ZF ventricle; this study addressed this point. Ventricular myocytes were obtained by enzymatic digestion. The patch clamp technique was used to record Na currents (INa), Ca currents (ICa) and action potentials (AP). Results are presented as mean±SE and assessed with paired t‐test. Single ventricular myocytes from ZF are long and thin, as described for other fish species. Cell capacitance was 25.5±0.9 pF (n=81). ICa density (at 0 mV) was −8.4±3.4 pA/pF and INa density (at −40 mV) was −106±18 pA/pF (n=6). Resting membrane potential was −66±2 mV (n=19). At 0.1 Hz stimulation frequency, AP duration at 25, 50, and 90% repolarization was 53±16, 117±26, 155±35 ms, respectively (n=12), indicating the presence of a plateau phase. Increasing stimulation frequency to 2 Hz significantly decreased AP duration (n=12, p<0.05). To conclude, we have developed a method to obtain viable isolated ventricle myocytes from ZF heart. The presence of a plateau during the AP suggests that this species might be appropriate for ion channels related mutation screening of cardiac alteration.

The in vivo study of cardiac mechano-electric and mechano-mechanical coupling during heart development in zebrafish

“…However, while Ca 2+handling mechanisms are also generally well conserved between zebrafish and humans (Rayani et al, 2018;van Opbergen, et al, 2018), aspects of excitation-contraction coupling do appear to differ. Zebrafish cardiomyocytes may be more dependent on extracellular Ca 2+ influx (including through T-type Ca 2+ channels) than intracellular sarcoplasmic reticulum Ca 2+ release for contraction, due to the apparent low Ca 2+ sensitivity of their ryanodine receptors (Bovo et al, 2013) and paucity of transverse tubules (Brette et al, 2008) (although others have shown a strong dependence of contractile force on the release of Ca 2+ from the sarcoplasmic reticulum (Haustein et al, 2015). Zebrafish also have a higher sodium-Ca 2+ exchanger current than in mammals, such that its reverse-mode has been shown to trigger sarcoplasmic reticulum Ca 2+ release (Zhang et al, 2011).…”