Decreased calcium channel currents and facilitated epinephrine release in the Ca²⁺ channel β3 subunit-null mice

The β subunits of voltage-dependent calcium channels are known to modify calcium channel currents through pore-forming α1 subunits. The β3 subunit is expressed in the adrenal gland and participates in forming various calcium channel types. We performed a series of experiments in β3-null mice to determine the role of the β3 subunit in catecholamine release from the adrenal chromaffin system. Protein levels of N-type channel forming CaV2.2 and L-type forming CaV1.2 decreased. The β3-null mice showed a decreased baroreflex, suggesting decreased sympathetic tonus, whereas plasma catecholamine levels did not change. Pulse-voltage stimulation revealed significantly increased amperometrical currents in β3-null mice, while patch-clamp recordings showed a significant reduction in Ca²⁺-currents due to reduced L- and N-type currents, indicating facilitated exocytosis. A biochemical analysis revealed increased InsP3 production. In conclusion, our results indicate the importance of the β3 subunit in determining calcium channel characteristics and catecholamine release in adrenal chromaffin cells.