Fig. 2.

Expression of CIRL increases the sensitivity of intact chromaffin cells to stimulation by α-Ltx. Chromaffin cells were transfected with plasmids for hGH (pXGH5) and either pCDR7, which encodes a newly cloned protein that binds α-Ltx (CIRL), or pCMVneo (a control) by calcium phosphate precipitates, as described. After 4 d the cells were incubated with the indicated concentrations of α-Ltx in PSS without Ca²⁺ or Mg²⁺ and with 0.1 mm EGTA. After 4 min, the toxin was removed, and the cells were incubated for an additional 5 min in PSS containing 2.2 mm Ca and 0.5 mm Mg. The amounts of hGH (A) and catecholamine (B) released into the medium and the amounts remaining in the cells were determined as described; n = 4 wells/group.