Voltage-dependent L-type Ca channels and a novel type of non-selective cation channel activated by cAMP-dependent phosphorylation in mesoderm-like (MES-1) cells.
Undifferentiated P19 embryonal carcinoma cells (ECC P19), the P19-derived clonal cell lines END-2 (visceral endoderm-like), EPI-7 (epithelioid ectoderm-like), MES-1 (mesoderm-like) and a parietal yolk sac cell line (PYS-2) were used as cellular models to examine the functional expression of voltage-dependent Ca channels and other Ca-permeable cation channels at various stages of early embryonic development. Whole-cell currents were recorded by means of the patch clamp technique. Whereas more than 75% of MES-1 cells possessed Ca channel currents, neither P19, END-2, EPI-7 nor PYS-2 cells had detectable voltage-dependent inward currents. Ca channel currents of MES-1 cells were highly sensitive towards 1,4-dihydropyridines and blocked by cadmium. Adrenaline (10 microM) caused Ca channel stimulation in only 14% of MES-1 cells examined. However, in 62% of the cells adrenaline activated a linear current component which under physiological conditions reversed close to 0 mV. Removal of extracellular Na+ suppressed the adrenaline-induced inward current, while reducing extracellular Cl- had no significant effect. These findings suggest that the adrenaline-induced current is carried through non-selective cation channels which were found to be permeable for Na+, K+, Cs+ >> Ca2+. Remarkably, the intracellular signalling pathway for activation of the non-selective cation current involved the cascade of reactions leading to cAMP-dependent phosphorylation, a regulatory pathway well known for cardiac Ca channels. A possible functional role of adrenaline-induced non-selective cation currents and Ca channels in embryonal development is discussed.
Kleppisch
T
T
Institut für Physiologie, Humboldt-Universität zu Berlin, F.R.G.
Wobus
A M
AM
Strübing
C
C
Hescheler
J
J
D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002277:Carcinoma / Q000503:physiopathology*; D000242:Cyclic AMP / Q000378:metabolism*; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology; D008648:Mesoderm / Q000502:physiology*; D010766:Phosphorylation; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D000242:Cyclic AMP; D004837:Epinephrine