NaCl-dependent expression of amiloride-blockable Na+ channel in Xenopus oocytes.
RNA was isolated from chicken lower intestine (both colon and coprodeum) and injected into Xenopus oocytes. 22Na+ fluxes measured after 1-4 days demonstrated the induction of an amiloride-blockable pathway. The Na+ transporter expressed by the exogenous RNA had a high affinity to amiloride (inhibitory constant less than 0.1 microM), but was insensitive to ethylisopropyl amiloride, i.e., it is likely to be the apical Na+ channel. Functional channels were readily expressed in oocytes injected with RNA derived from chickens fed a low-NaCl diet. On the other hand, no channel activity was detected in oocytes injected with RNA isolated from chickens fed a high-NaCl diet. Thus the previously reported regulation of transport by the dietary NaCl intake involves modulations in the level of mRNA that codes either for the Na+ channel or a posttranscriptional regulator of the channel.
Asher
C
C
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
Singer
D
D
Eren
R
R
Yeger
O
O
Dascal
N
N
Garty
H
H
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D002645:Chickens / Q000235:genetics; D004039:Diet, Sodium-Restricted; D004594:Electrophysiology; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism; D008845:Microinjections; D009865:Oocytes / Q000378:metabolism*; D012313:RNA / Q000032:analysis; D012964:Sodium / Q000493:pharmacokinetics / Q000502:physiology; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology*; D014982:Xenopus laevis
D015222:Sodium Channels; C039465:5-dimethylamiloride; D012965:Sodium Chloride; D012313:RNA; D000584:Amiloride; D012964:Sodium