L-type calcium channels are preferentially coupled to endocytosis in bovine chromaffin cells

Exocytosis and endocytosis are Ca2+-dependent processes. The contribution of high-voltage activated Ca2+ channels subtypes to exocytosis has been thoroughly studied in chromaffin cells. However, similar reports concerning endocytosis are unavailable. Thus, we studied here the effects of blockers of L (nifedipine), N (ω-conotoxin GVIA) and P/Q (ω-agatoxin IVA) Ca2+ channel on Ca2+ currents (ICa), Ca2+ entry (QCa), as well as on the changes in membrane capacitance (Cm) in perforated-patch voltage-clamped bovine adrenal chromaffin cells. Using 500-ms pulses to 0 or +10 mV, given from a holding potential of −80 mV and 2 mM Ca2+ we found that ω-conotoxin GVIA affected little the exo-endocytotic responses while ω-agatoxin IVA markedly blocked those responses. However, nifedipine blocked little exocytosis but almost completely inhibited endocytosis. We conclude that L-type Ca2+ channels seem to be selectively coupled to endocytosis.