RESUMEN
INTRODUCTION: The aims of this study were to investigate: (1) the effect of supplementing the culture medium on preservation of L-type calcium channel current (1Ca,L) in adult rabbit ventricular myocytes cultured for 4 days; and (2) preservation of the ICa,L response in cultured myocytes to the beta-adrenergic agonist isoprenaline. METHODS AND RESULTS: Adult rabbit myocytes were cultured on laminin-pretreated glass coverslips. The basic, serum-free culture medium was supplemented with 2 mM L-carnitine, 5 mM creatine, and 5 mM taurine. Myocytes were whole cell patch-clamped, and the L-type Ca channel current was recorded selectively as Ba flux (IBa,L) via the channels. IBa,L density (i.e., IBa,L amplitude normalized to membrane capacitance) in myocytes maintained in supplemented medium did not change significantly during culture (P > 0.1). By comparison, IBa,L density in myocytes cultured in nonsupplemented medium declined by 36% after 24 hours in culture (day 1) and then recovered by the fourth day (day 4). There was no significant difference in the response to isoprenaline of acutely isolated myocytes and 4-day cultured myocytes. Isoprenaline 100 nM increased peak IBa,L by 149% +/- 32% (mean +/- SEM) in acutely isolated myocytes (n = 4 cells), and by 224% +/- 60% (n = 6 cells) and 159% +/- 24% (n = 8 cells) in day 1 and 4 cultured myocytes, respectively. CONCLUSIONS: Supplemented medium improved IBa,L density in cultured myocytes. beta-Adrenergic receptors and intracellular messenger pathways appear to remain intact in adult rabbit myocytes cultured for up to 4 days.