Separate Cl- conductances activated by cAMP and Ca2+ in Cl(-)-secreting epithelial cells.

AUTOR(ES)

Cliff, W H

RESUMO

We studied the cAMP- and Ca2(+)-activated secretory Cl- conductances in the Cl(-)-secreting colonic epithelial cell line T84 using the whole-cell patch-clamp technique. Cl- and K+ currents were measured under voltage clamp. Forskolin or cAMP increased Cl- current 2-15 times with no change in K+ current. The current-voltage relation for cAMP-activated Cl- current was linear from -100 to +100 mV and showed no time-dependent changes in current during voltage pulses. Ca2+ ionophores or increased pipette Ca2+ increased both Cl- and K+ currents 2-30 times. The Ca2(+)-activated Cl- current was outwardly rectified, activated during depolarizing voltage pulses, and inactivated during hyperpolarizing voltage pulses. Addition of ionophore after forskolin further increased Cl- conductance 1.5-5 times, and the current took on the time-dependent characteristics of that stimulated by Ca2+. Thus, cAMP and Ca2+ activate Cl- conductances with different properties, implying that these second messengers activate different Cl- channels or that they induce different conductive and kinetic states in the same Cl- channel.

Documentos Relacionados

• Ca2+ sensitivity of volume-regulatory K+ and Cl- channels in cultured human epithelial cells.
• Ca2+ and Ca(2+)-activated Cl- currents in rabbit oesophageal smooth muscle.
• Hormone secretagogues increase cytosolic calcium by increasing cAMP in corticotropin-secreting cells.
• Swelling- and cAMP-activated Cl- currents in isolated rat carotid body type I cells.
• cAMP controls cytosolic Ca2+ levels in Dictyostelium discoideum