Functional expression of urea channels in amphibian oocytes injected with frog urinary bladder mRNA.
In amphibian urinary bladder epithelium, vasopressin increases passive urea permeability, concomitant with the appearance of a facilitated urea transport. Amphibian oocytes from Xenopus laevis and Rana esculenta were microinjected with total or fractionated poly(A+) RNA isolated from frog urinary bladder epithelial cells. After several (3-5) days at 18 degrees C, the urea flux was assayed by measuring the uptake and efflux of [14C]urea in water-injected and mRNA-injected oocytes. A 2 to 3-fold increase of urea transport was detected in oocytes injected either with total mRNA or with a 6-10 kilobase mRNA fraction, when compared with water-injected oocytes. This expression of urea channels was inhibited by 0.1 mM phloretin (50% inhibition) and 0.1 mM nitrophenylthiourea (up to 70% inhibition). On the contrary, no expression was detected in brain mRNA-injected oocytes. These results show the specific functional expression of the phloretin- and NPTU-sensitive urea channel (or carrier) from frog urinary bladder epithelial cells, providing an approach for the expression cloning of these urea channels.
Martial
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Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes Nucléaires de Saclay, Gif-Sur-Yvette, France.
Ripoche
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Ibarra
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D000818:Animals; D004848:Epithelium / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000235:genetics*; D007700:Kinetics; D008845:Microinjections; D009596:Nitrophenols / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D010693:Phloretin / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics*; D011893:Rana esculenta; D014170:Transformation, Genetic; D014508:Urea / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism*; D014982:Xenopus laevis
D007473:Ion Channels; D009596:Nitrophenols; D012333:RNA, Messenger; D014508:Urea; D010693:Phloretin