ISSN:
1432-1912
Schlagwort(e):
Muscarinic receptor
;
Potassium channel
;
Single atrial cells
;
GTP-binding proteins
;
N-ethylmaleimide
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Summary The effects of N-ethylmaleimide (NEM), a sulfhydryl alkylating agent, on the ACh-activated K+ current were examined in single cells from rabbit hearts using whole-cell and single channel patch clamp techniques. Bath application of NEM (50 μM) or the muscarinic antagonist, atropine (1 μM) completely inhibited the ACh-activated K+ current in whole-cell recordings. In cell-attached patch conditions, the inhibitory effect of NEM was still observed; in contrast, atropine was ineffective when the agents were bath applied, indicating that the site of action of NEM is different from that of atropine. Inside-out patch recordings confirmed that GTP was required on the internal side of the membrane for activation of this K+ channel when ACh was present in the pipette. NEM abolished this GTP-activated K+ channel activity. GTPγS, a non-hydrolysable GTP analogue, was able to activate this K+ channel in the absence of a muscarinic agonist, an effect thought to be due to the direct activation of GTP-binding proteins. Pretreatment with NEM almost completely prevented this effect of GTPγS. In contrast, after the activation of the K+ channel by GTPγS had reached a steady-state, NEM failed to show a significant inhibitory effect. These results demonstrate that NEM prevents the activation of muscarinic receptor-regulated K+ channel and suggest an involvement of alkylation of the GTP-binding proteins which are coupled to this type of K+ channel.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00180671
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