CELL-DISSOCIATION WITH PAPAIN REDUCES THE DENSITY OF CGMP-ACTIVATED CHANNELS OF THE RETINAL ROD

A proteolytic enzyme, papain, is the enzyme commonly used for dissocia tion of retinal neurons. To ask whether papain modifies the activity o f ion channels, cGMP-activated channels were recorded in inside-out me mbrane patches excised from the bullfrog rod outer segment, and the ac tivity was compared between cells dissociated using papain and cells d issociated mechanically. While the affinity to cGMP, I-V relation, cha nnel kinetics, and single-channel current amplitude were almost the sa me in both papain-treated and the control preparations, the total curr ent flowing through the patch membrane of the papain-treated cells was reduced to about 20% of the control, suggesting that papain reduced t he density of cGMP-activated channels.