PROGESTERONE INHIBITION OF WATER PERMEABILITY IN BUFO-ARENARUM OOCYTES AND URINARY-BLADDER

The ovarian oocytes from Bufo arenarum (BAO) but not those from Xenopu s laevis (XLO) would have water channels (WC). We now report that the injection of the mRNA from BAO into the oocytes from XLO increased the ir water osmotic permeability (P-f) (reduced by 0.3 mM HgCl2 and rever sed by 5 mM beta-mercaptoethanol). A 30-min challenge with progesteron e induced, 18 h later, a reduction of the mercury-sensitive fraction o f P-f in the BAO (but not in XLO). The mRNA from BAO pretreated with p rogesterone lost its capacity to induce WC in the XLO, but the hormone did not affect the expression of the WC in XLO previously injected wi th the mRNA from BAO. P-f was also measured in urinary bladders of BAO . Eighteen hours after a challenge with progesterone, a reduction in t he hydrosmotic response to oxytocin was observed. Finally, the mRNA fr om the urinary bladder of BAO was injected into XLO. An increase in P- f was observed. This was not the case if, before the mRNA extraction, the bladders were treated with progesterone. We conclude that the BAO WC share progesterone sensitivity with the oxytocin-regulated water ch annel present in the toad urinary bladder.