XB-ART-3534Am J Physiol Heart Circ Physiol. June 1, 2004; 286 (6): H2035-41.
Characterization of embryonic cardiac pacemaker and atrioventricular conduction physiology in Xenopus laevis using noninvasive imaging.
Congenital heart defects often include altered conduction as well as morphological changes. Model organisms, like the frog Xenopus laevis, offer practical advantages for the study of congenital heart disease. X. laevis embryos are easily obtained free living, and the developing heart is readily visualized. Functional and morphological evidence for a conduction system is available for adult frog hearts, but information on the normal properties of embryonic heart contraction is lacking, especially in intact animals. With the use of fine glass microelectrodes, we were able to obtain cardiac recordings and make standard electrophysiological measurements in 1-wk-old embryos (stage 46). In addition, a system using digital analysis of video images was adapted for measurement of the standard cardiac intervals and compared with invasive measurements. Video images were obtained of the heart in live, pharmacologically paralyzed, stage 46 X. laevis embryos. Normal values for the timing of the cardiac cycle were established. Intervals determined by video analysis (n = 53), including the atrial and ventricular cycle lengths (473 +/- 10 ms and 464 +/- 19 ms, respectively) and the atrioventricular interval (169 +/- 5 ms) were not statistically different from those determined by intrathoracic cardiac recordings. We also present the data obtained from embryos treated with standard medications that affect the human conduction system. We conclude that the physiology of embryonic X. laevis cardiac conduction can be noninvasively studied by using digital video imaging. Additionally, we show the response of X. laevis embryonic hearts to chronotropic agents is similar but not identical to the response of the human heart.
PubMed ID: 15148055
PMC ID: PMC3530895
Article link: Am J Physiol Heart Circ Physiol.
Grant support: HL 62178 NHLBI NIH HHS , HL 62483 NHLBI NIH HHS , T32 HL 07413 NHLBI NIH HHS , P50 HL062178-050003 NHLBI NIH HHS , P50 HL062178 NHLBI NIH HHS , T32 HL007413 NHLBI NIH HHS , R01 HL062483 NHLBI NIH HHS , R56 HL062483 NHLBI NIH HHS