Membrane-delimited activation of muscarinic K current by an albumin-associated
factor in guinea-pig atrial myocytes
Pflugers Arch, 425 (3-4):
329-34 (November 1993)Bunemann, M Pott, L Research Support, Non-U.S. Gov't Germany Pflugers
Archiv : European journal of physiology Pflugers Arch. 1993 Nov;425(3-4):329-34..Abstract
Atrial myocytes obtained by enzymatic perfusion of hearts from adult
guinea-pigs and cultured for 0-14 days were studied using different
configurations of the patch-clamp technique. Activation of muscarinic
K current IK(ACh) in whole-cell voltage-clamp mode by strongly
diluted sera from various sources could be mimicked by corresponding
concentrations of albumin, but not by delipidated ("fatty-acid-free")
samples of albumin. In cell-attached membrane patches activity of
IK(ACh) channels was significantly higher than basal IK(ACh) channel
activity, if the pipette contained serum, whereas application of
serum-containing solution to the cell outside the patch did not affect
channel activity. In isolated inside-out membrane patches, strong
IK(ACh) activation by internal guanosine triphosphate (GTP, 5 microM)
was observed if the pipette contained serum. If no activator was
presented to the outer face of the membrane, only weak opening activity
was observed during bath application of GTP. These results demonstrate
that the serum factor which causes activation of IK(ACh) is associated
with albumin. Furthermore activation of IK(ACh) by that factor proceeds
analogous to ACh or adenosine, i.e. via a membrane-delimited receptor,
G-protein, channel interaction.