AJP - Cell Physiology, Vol 232, Issue 5 174-C179, Copyright © 1977 by American Physiological Society
Effects of 3'-deoxycytidine on rRNA synthesis in toad bladder: analysis of response to aldosterone
B. C. Rossier, P. A. Wilce, J. F. Inciardi, F. K. Yoshimura and I. S. Edelman
Previous studies showed that aldosterone augments transepithelial active
Na+ transport and the incorporation of [3H]uridine into polyadenylated RNA
(poly(A)(+)-RNA) (putatively mRNA) early in the latent period. Soon
thereafter, incorporation of [methyl-14C] groups, as well as [3H]uridine
into rRNA is also increased. To evaluate the role of rRNA in
mineralocorticoid action, the inhibitor 3'-deoxycytidine was used in
studies on the urinary bladder of the toad Bufo marinus. 3'-deoxycytidine
suppressed the incorporation of [methyl-14C] and [3H]uridine into nuclear
precursors of rRNA and subunits of cytoplasmic rRNA. In contrast,
3'-deoxycytidine inhibited incorporation of ]3H]uridine into cytoplasmic
poly(A)(+)-RNA minimally. In control experiments, 3'-deoxycytidine had no
significant effect on Na+ transport, measured as the short-circuit current
(scc), when given alone. 3'-Deoxycytidine also had no significant effect on
the aldosterone-dependent increase in scc. In the presence of
3'-deoxycytidine, aldosterone enhanced both the scc and the incorporation
of [3H]uridine into poly(A)(+)-RNA significantly. We conclude that during
the first 3 h, the mineralocorticoid action of aldosterone is not sensitive
to inhibition of rRNA synthesis. Previous studies, however, implicate mRNA
synthesis in this early response.
