CYSTIC-FIBROSIS AFFECTS SPECIFIC CELL-TYPE IN SWEAT GLAND SECRETORY COIL

The sweat gland has three distinct cell types: a myoepithelial (ME) ce ll, a beta-adrenergic-insensitive (beta-I) cell, and a beta-adrenergic -sensitive (beta-S) cell. Using intracellular microelectrodes, we soug ht to functionally identify the specific cell type(s) affected in cyst ic fibrosis (CF). We found that in CF secretory coils 1) the ME cells are unaffected, as indicated by normal cell membrane potentials and sp ontaneous and cholinergically induced depolarizing potentials, 2) the beta-I cells showed normal physiological properties, including a relat ively smaller cell membrane potential (approx -25 mV) and a Ba2+-inhib itable cholinergic response, and, in contrast, 3) the beta-S cell is a bnormal, as shown by the lack of a beta-adrenergically activated cysti c fibrosis transmembrane conductance regulator (CFTR) Cl- conductance (G(Cl)). Lack of CFTR G(Cl) in this cell type does not affect either t he magnitude of cell membrane potential (approx -56 mV) or the relativ e cell membrane G(Cl) or the cholinergic response, as compared with th at of normal beta-S cells. We conclude that, of the three cell types i n secretory coil, only the beta-S cell is specifically affected in the CF secretory tissue of the human sweat gland.