Identification of apamin binding sites in rat intestinal mucosa.
Apamin, a specific blocker of one class of Ca(2+)-activated K+ channes, was used to detect the apamin receptors associated with K+ channels in the mucosa of the rat jejunum and colon. Two receptor sites for 125I-apamin have been identified. These sites differed in their affinity for apamin (jejunum: KD1 = 1.1 nM and KD2 = 170 nM; colon: KD1 = 0.5 nM and KD2 = 1.1 nM and KD2 = 140 nM) and the maximum number of sites (jejunum: B(max1) = 111 and B(max2) = 4030; colon: B(max1) = 187 and B(max2) = 7550 fmol/mg of protein). 125I-apamin binding was stimulated by K+ ions with K0.5 = 1.0 mM and inhibited by the neuromuscular blocker tubocurarine (KI = 50 microM). We interpret these data to demonstrate that the high-affinity, low-capacity binding sites reflect the existence of apamin-sensitive K+ channels in the intestinal mucosa.
Pácha
J
J
Institute of Physiology, Czechoslovak Academy of Sciences, Prague.
Vorlicek
J
J
Teisinger
J
J
D000818:Animals; D001030:Apamin / Q000378:metabolism*; D003106:Colon; D007413:Intestinal Mucosa / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D007583:Jejunum; D007700:Kinetics; D008297:Male; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D014403:Tubocurarine / Q000494:pharmacology
D015221:Potassium Channels; D017981:Receptors, Neurotransmitter; C033799:apamin receptor; D001030:Apamin; D011188:Potassium; D014403:Tubocurarine