PRESENCE OF ZINC AND CALCIUM PERMEANT CHANNELS IN THE INNER MEMBRANE OF THE NUCLEAR-ENVELOPE

The nuclear envelope possesses specific ion channels that regulate the ionic traffic between the cytoplasm or the perinuclear space and the nucleoplasm. Using the patch-clamp technique to isolated rat nuclei ex hibiting only the inner membrane of the nuclear envelope, we report th e existence of calcium and zinc permeant channels. These channels disp layed similar characteristics (conductance : 8 and 11 pS respectively, open time constant (3.5 ms and 3.7 ms) and close time constant (5.1 m s and 4.8 ms)) and were insensitive to different types of calcium chan nels blockers and to calcium concentration in the bathing solution. Th e exact role of these channels remains to define, but they may contrib ute to the regulation of intranuclear Ca++ or Zn++ dependent processes as important as cell proliferation or programmed cell death. Moreover , this work demonstrates that our nuclei preparation provides a way to study the inner membrane of the nuclear envelope. (C) 1997 Academic P ress.