CARDIOMYOCYTE ELECTROPHYSIOLOGICAL PARAMETERS OF THE FRUIT BAT ARTIBEUS LITURATUS

Bats (order Chiroptera) are the only mammals capable of powered flight, an exceptionally efficient mode of locomotion in terms of distance traveled per unit time, yet also the most energetically demanding. During flight, the heart rate of certain bat species can reach approximately 1000 beats per minute, drawing attention to the unique electrophysiological mechanisms that support such intense cardiac activity. In this study, we present electrophysiological recordings from left ventricular cardiomyocytes of the fruit bat Artibeus lituratus. Eleven wild adult males were captured using mist nets under ICMBio permit number 83724-2. Animals were anesthetized with isoflurane and euthanized by decapitation, following procedures approved by the CEUA-UFMG (protocol 108/2023). Hearts were excised and left ventricular cardiomyocytes were enzymatically isolated for analysis. Action potentials (APs) were recorded using whole-cell patch-clamp at stimulation frequencies of 1 Hz and 3 Hz in current clamp mode, alongside measurements of macroscopic IK₁ and I_Ca currents in voltage clamp mode. All experiments were conducted at room temperature (23 - 25 °C). Cardiomyocytes from A. lituratus displayed a resting membrane potential of -86.5 ± 3.6 mV and a peak potential of 47.2 ± 10.8 mV (9 cells /5 individuals). Phase 0 presented a maximum depolarization rate of 226.57 ± 75.05 mV/ms (9/5), and phase 1 showed a modest notch. The duration at 90% repolarization (APD90) exhibited high variability: at 1 Hz, the mean APD90 was 309.4 ± 171.9 ms (range: 76.6 – 879.4 ms, 9/5); at 3 Hz, it averaged 221.5 ± 167.4 ms (range: 69.0 – 499.1 ms, 5/2). Phase 2 exhibited a mean maximum repolarization rate of -0.35 ± 0.25 mV/ms at 1 Hz (9/5) and of -0.7 ± 0.47 mV/ms at 3 Hz (5/2). IK₁ current density peaked at -6.7 ± 2.8 pA/pF at -120 mV (12/8), while I_Ca reached a maximum of -2.72 ± 1.79 pA/pF at -10 mV (7/4), with a mean recovery τ of 23.37 ± 20.79 ms. The pronounced variability in APD suggests that additional modulatory mechanisms, such as temperature sensitivity, may influence cardiac electrical activity in this species.