AJP - Gastrointestinal and Liver Physiology, Vol 262, Issue 2 244-G248, Copyright © 1992 by American Physiological Society

ARTICLES

NaCl-dependent expression of amiloride-blockable Na+ channel in Xenopus oocytes

C. Asher, D. Singer, R. Eren, O. Yeger, N. Dascal and H. Garty
Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.

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.

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