The zebrafish is widely used for human related disease studies. Surprisingly, there is no information about the electrical activity of single myocytes freshly isolated from adult zebrafish ventricle. In this study, we present an enzymatic method to isolate ventricular myocytes from zebrafish heart that yield a large number of calcium tolerant cells. Ventricular myocytes from zebrafish were imaged using light and confocal microscopy. Myocytes were mostly rod shaped and responded by vigorous contraction to field electrical stimulation. Whole cell configuration of the patch clamp technique was used to record electrophysiological characteristics of myocytes. Action potentials present a long duration and a plateau phase and action potential duration decreases when increasing stimulation frequency (as observed in larger mammals). Together these results indicate that zebrafish is a species ideally suited for investigation of ion channels related mutation screening of cardiac alteration important in human.

With the globalization of clinical trials, regulators have increased collaboration to evaluate the adequacy of clinical trial conduct and to optimize regulatory oversight. The 2020 joint Good Clinical Practice (GCP) symposium of the US Food and Drug Administration and the UK Medicines and Healthcare products Regulatory Agency provided the agencies’ perspectives on the challenges in ensuring data quality in novel clinical trial designs and the importance of the management and documentation of protocol deviations, sponsor oversight of clinical trials, and use of electronic source data, including electronic health records. This paper summarizes considerations of both agencies on these topics, along with case examples. This paper touches upon considerations when using real‐world data to support regulatory decisions. It also discusses the impact of the coronavirus disease 2019 (COVID‐19) pandemic on clinical trial conduct and underscores the importance of well‐designed, resilient, and adaptable systems for GCP compliance and data integrity.

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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.

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