The Involvement of Ser1898 of the Human L-Type Calcium Channel in Evoked Secretion
Figure 6
Forskolin accelerates secretion to the same extent in Hu/wt- and Hu/S1898A-infected cells. Amperometry currents were elicited by a 10 sec puff of 60 mM KCl (K60) as indicated by the arrow, in chromaffin cells infected with pSFV containing Hu/wt (left) or Hu/S1898A (right) in the presence of 1 μM forskolin and 5 M nifedipine. (a) Representative single amperometric events in Hu/wt or Hu/S1898A infected cells, with and without forskolin. (b) The cumulative number of events per cell averaged for Hu/wt- and Hu/S1898A-infected cells ( and ), with or without forskolin ( and ), was plotted versus time. An expanded view of the initial cumulative spike counts plotted versus time (lower). (c) The initial rates of secretion were calculated from the linearization of the cumulative averaged spike count (left). Means were calculated for individual cells as an average from more than 500 spikes; see Table SI. Total amount of catecholamine secreted was quantified by averaging of the total mean charge. Summation of spike areas in cells infected with Hu/wt (empty columns) or Hu/S1898A (gray columns) during time range of 10–40 sec (right); *.
