Activation of osmotically-activated potassium transporters after injection of mRNA from A6 cells in Xenopus oocytes.
The different potassium pathways, under iso-osmotic or hypo-osmotic conditions, were examined in Xenopus oocytes that were micro-injected with mRNA from A6 cells. Hypo-osmotically stimulated 86Rb (K+) effluxes could be measured from intact oocytes 1-4 days after injection of 25 ng of poly (A)+ RNA isolated from A6 cells. 86Rb (K+) effluxes were 2.2 times higher from oocytes micro-injected with 25 ng of poly(A)+ RNA, than from water injected control oocytes. Water-injected oocytes themselves, however, were 7-fold more responsive to a hypo-osmotic shock than non-injected Xenopus oocytes. There was no significant effect of the different K+ transport blockers tested (TEA, bumetanide, glybenclamide or quinidine) on the endogenous 86Rb (K+) effluxes from non-injected oocytes in either iso- or hypo-osmotic media. The 86Rb (K+) effluxes from water-and mRNA-injected oocytes in hypo-osmotic media were both inhibited by TEA. In mRNA-injected oocytes the increase in 86Rb (K+) transport following a medium dilution was also inhibited in the presence of glybenclamide or bumetanide. The present study reports that the activation of hypo-osmotically-activated potassium transporters in the oocytes of Xenopus laevis. after injection of mRNA from A6 cells differs quantitatively and in part qualitatively (glybenclamide-sensitivity) from the endogenous K+ pathways of non-injected and of water-injected Xenopus oocytes.
Ratcliff
F G
FG
Department of Cellular and Molecular Biology, Laboratoire Jean Maetz B.P. 68, Villefranche/Mer, France.
Ehrenfeld
J
J
D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D005905:Glyburide / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011802:Quinidine / Q000494:pharmacology; D012333:RNA, Messenger / Q000302:isolation & purification / Q000494:pharmacology*; D012414:Rubidium Radioisotopes; D014162:Transfection; D014982:Xenopus laevis
D002352:Carrier Proteins; D012333:RNA, Messenger; D012414:Rubidium Radioisotopes; D002034:Bumetanide; D011802:Quinidine; D011188:Potassium; D005905:Glyburide