Effects of 3'-deoxycytidine on rRNA synthesis in toad bladder: analysis of response to aldosterone

1977 ◽  
Vol 232 (5) ◽  
pp. C174-C179 ◽  
Author(s):  
B. C. Rossier ◽  
P. A. Wilce ◽  
J. F. Inciardi ◽  
F. K. Yoshimura ◽  
I. S. Edelman
Keyword(s):  
Urinary Bladder ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Early Response ◽  
Rrna Synthesis ◽  
Mrna Synthesis ◽  
Na Transport ◽  
Polyadenylated Rna ◽  
Toad Bufo

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.

Inhibitory effect of phorbol ester on sodium transport in frog urinary bladder

1990 ◽  
Vol 259 (3) ◽  
pp. F425-F431
Author(s):  
T. Satoh ◽  
H. Endou
Keyword(s):  
Urinary Bladder ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Inhibitory Influence ◽  
Dependent Manner ◽  
Camp Accumulation ◽  
Frog Urinary Bladder ◽  
Na Transport

To confirm the role of protein kinase C (PKC) on epithelial Na transport, we studied the effects of phorbol 12-myristate 13-acetate (PMA) and dioctanoylglycerol (DiC8), activators of PKC, on short-circuit current (Isc) in frog urinary bladder and further examined the influence of sphingosine, an inhibitor of PKC, on PMA- or DiC8-modulated Isc. PMA reduced basal Isc in a dose-dependent manner, and sphingosine (10 and 100 microM) partially restored PMA-reduced Isc. On the other hand, DiC8 (5 x 10(-5) M) also reduced basal Isc, and this action was completely prevented by 100 microM sphingosine. Both PMA (4 x 10(-5) M) and DiC8 inhibited vasopressin (50 mU/ml)- and forskolin (5 x 10(-5) M)-stimulated increases in Isc. PMA (4 x 10(-5) M) also inhibited 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP)-stimulated increase in Isc. Furthermore, PMA (4 x 10(-5) M) and DiC8 (5 x 10(-5) M) inhibited vasopressin (50 mU/ml)-stimulated cAMP accumulation. DiC8 also inhibited forskolin-stimulated cAMP accumulation. These results indicate that PMA exerts inhibitory influence on Na transport mainly by its own potency of PKC activation. In addition, it is suggested that there is a cross talk in epithelial Na transport between PKC and cAMP-dependent pathway in frog urinary bladder.

HCO3-Cl exchange transport in the adaptive response to alkalosis by turtle bladder

1980 ◽  
Vol 239 (2) ◽  
pp. F167-F174
Author(s):  
L. Cohen
Keyword(s):  
Urinary Bladder ◽  
Adaptive Response ◽  
Intact Animal ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Transport ◽  
Acid Base ◽  
Turtle Bladder ◽  
Acid Base Status ◽  
Ph Stat

The isolated turtle urinary bladder acidifies its mucosal (M) solution, and the rate of acidification (JH) is equivalent to the short-circuit current after Na+ transport is abolished by ouabain. When HCO3(-) is present in the serosal solution it is secreted into M in an electroneutral exchange for absorbed Cl-. The rate of HCO3(-) secretion (JHCO3(-)) can be measured by pH stat titration after JH is nullified by an opposing pH gradient. With use of these methods JH and JHCO3 were measured sequentially in bladdes from control animals and animals fed NaHCO3 (alkalosis) or NH4Cl (acidosis). JH in alkalosis (57 +/- 6 micro A) was ot different from control values (53 +/- 7 micro A). JHCO3, however, was nearly 40% higher in alkalosis (1.63 +/- 0.11 vs. 1.17 +/- 0.14 mu mol x h-1 x 8 cm-2). In contrast, JHCO3 in acidosis was similar to control values (0.89 +/- 0.15 mu mol x h-1 x 8 cm-2) but JH was increased. As judged from Cl- fluxes, neither alkalosis nor acidosis altered the electroneutral coupling between HCO3(-) secretion and Cl- absorption. JH and JHCO3 appear to be independent processes in the turtle bladder that are capable of responding independently to physiologic changes in the acid-base status of the intact animal.

Tetracycline-induced inhibition of Na+ transport in the toad urinary bladder

1978 ◽  
Vol 235 (4) ◽  
pp. F359-F366 ◽  
Author(s):  
J. Guzzo ◽  
M. Cox ◽  
A. B. Kelley ◽  
I. Singer
Keyword(s):  
Urinary Bladder ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Lipid Solubility ◽  
Toad Urinary Bladder ◽  
Na Transport ◽  
Ussing Chambers ◽  
Incubation Periods ◽  
Active Conductance ◽  
Drug Protein Binding

The effects of three tetracyclines, demethylchlortetracycline (DMC), minocycline (MNC), and oxytetracycline (OTC), on Na+ transport (measured as short-circuit current) were examined in toad urinary bladders mounted in modified Ussing chambers. During a 1-h incubation period serosal DMC (but not MNC or OTC) inhibited basal Na+ transport, whereas MNC (but not DMC or OTC) inhibited ADH-stimulated Na+ transport. MNC also inhibited cyclic AMP-stimulated Na+ transport. During longer incubation periods all three drugs inhibited basal Na+ transport. The DMC-induced inhibition of basal Na+ transport and the MNC-induced inhibition of ADH-stimulated Na+ transport were paralleled by an inhibition of the active conductance of the bladders. Thus, although all three drugs inhibit basal Na+ transport, only MNC inhibits ADH-stimulated Na+ transport. This effect does not correlate with the known effects of the tetracyclines on ADH-stimulated water flow or with drug-protein binding, and may be related to the greater lipid solubility of MNC.

Effect of brefeldin A on ADH-induced transport responses of toad bladder

1994 ◽  
Vol 266 (4) ◽  
pp. C1069-C1076 ◽  
Author(s):  
K. Weng ◽  
J. B. Wade
Keyword(s):  
Water Permeability ◽  
Short Circuit ◽  
Brefeldin A ◽  
Membrane Traffic ◽  
Short Circuit Current ◽  
Toad Urinary Bladder ◽  
Membrane Biogenesis ◽  
Na Transport ◽  
Stimulation Of

We have used brefeldin A (BFA) to examine the role of membrane traffic in the short-circuit current (ISC) and water permeability responses of the toad urinary bladder. BFA treatment of 1 or 5 micrograms/ml had a complex effect on the response of the ISC to antidiuretic hormone (ADH) or forskolin stimulation. Although the responses to initial challenges by ADH were not impaired by BFA, subsequent ISC responses were progressively reduced. Similarly, while the response to an initial challenge by forskolin was modestly reduced by BFA, subsequent responses were markedly reduced. Inhibition of protein synthesis with cycloheximide (CHM) affected ISC responses similarly. Neither BFA nor CHM had an effect on water permeability responses. These observations show that although the membrane traffic responsible for the water permeability response is insensitive to inhibition by BFA or CHM, the stimulation of Na+ transport becomes increasingly sensitive to these inhibitors with successive challenges by ADH or forskolin. Although initial increases in Na+ transport utilize preexisting components, subsequent responses appear to require an intact system for membrane biogenesis.

Aldosterone and insulin effects on driving force of Na+ pump in toad bladder

1976 ◽  
Vol 230 (6) ◽  
pp. 1603-1608 ◽  
Author(s):  
B Siegel ◽  
MM Civan
Keyword(s):  
Urinary Bladder ◽  
Driving Force ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Toad Bladder ◽  
Na Transport ◽  
Na Pump ◽  
Before And After

Both aldosterone and insulin increase active Na+ transport across the urinary bladder of the toad. Recent data have provided further support to the concept that aldosterone acts primarily to increase Na+ entry from the mucosal medium into the transporting cells, whereas insulin acts to increase active Na+ extrusion into the serosal medium. To examine this concept further, the driving force (E(Na)) of the Na+ pump was measured, by the technique described by Yonath and Civan (48), before and after hormonal administration. Both hormones increased short-circuit current, but only insulin increased E(Na). The validity of the technique was further explored by imposing periods of hypoxia upon a series of experimental hemibladders; as expected, hypoxia reversibly decreased E(Na). The data indicate that insulin stimulates Na+ transport, in part by directly stimulating the Na+ pump. The results are also consistent with the concept that aldosterone stimulates net Na+ movement solely by enhancing Na+ entry into the transporting cells, but are subject to alternative interpretations.

Insulin-mediated Na+ transport in the toad urinary bladder

1977 ◽  
Vol 232 (3) ◽  
pp. F270-F277
Author(s):  
M. Cox ◽  
I. Singer
Keyword(s):  
Urinary Bladder ◽  
Initial Rate ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Mechanisms Of Action ◽  
Maximal Response ◽  
Toad Urinary Bladder ◽  
Na Transport ◽  
Ussing Chambers ◽  
K Concentration

The characteristics of insulin-induced Na+ transport in the toad urinary bladder were determined and compared to those of aldosterone. Bladders were mounted in modified Ussing chambers, and standard short-circuit current techniques were employed to measure transepithelial Na+ transport. Insulin added to the serosal medium is much more effective than insulin added to the mucosal medium. Serosal insulin concentrations from 10(1) to 10(3) muU/ml increase both the initial rate and the final level of Na+ transport achieved, whereas concentrations from 10(3) to 10(5) muU/ml increase only the initial rate of Na+ transport. Insulin-induced Na+ transport probably does not require glucose. Both insulin- and aldosterone-induced Na+ transport are directly proportional to serosal (but not mucosal) K+ concentration over the physiologic range (2.0-7.0 meq/liter). However, cycloheximide abolishes aldosterone- but not insulin-induced Na+ transport. In addition, insulin stimulates Na+ transport after a maximal response to aldosterone, and aldosterone stimulates Na+ transport after a maximal response to insulin. Thus, although they have several similar characteristics, insulin and aldosterone have at least partially independent mechanisms of action on Na+ transport in the toad urinary bladder.

Ion and water transport by the flounder urinary bladder: salinity dependence

1984 ◽  
Vol 246 (4) ◽  
pp. F395-F401 ◽  
Author(s):  
J. R. Demarest
Keyword(s):  
Hydraulic Conductivity ◽  
Urinary Bladder ◽  
Ion Transport ◽  
Water Transport ◽  
Fluid Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Transepithelial Resistance ◽  
Na Transport ◽  
Ion Movement

Urinary bladders from seawater-acclimated (SW) flounder had a transepithelial resistance (Rt) of congruent to 2,000 omega X cm2 and absorbed Na and Cl at equal rates of about 3 mueq X cm-2 X h-1 in an electrically silent manner; the short-circuit current (Isc) was 0.03 +/- 0.01 mueq X cm-2 X h-1. The transport of Na and Cl was only partially coupled. Removal of Na (or Cl) from the bathing solutions reduced net Cl (or Na) absorption by only 60%, yet there was neither a change in transepithelial potential nor the appearance of a short-circuit current that could be associated with the net Cl (or Na) transport that remained. Bladders from freshwater-acclimated (FW) flounder had a fivefold lower Rt and exhibited the same partially coupled and equal Na and Cl transport, but the ion transport rates were twice as large as those of SW bladders and the bladders exhibited a significant Isc of 0.51 +/- 0.08 mueq X cm-2 X h-1. The rate of fluid transport was much lower in FW than in SW bladders, reflecting a sixfold decrease in hydraulic conductivity (Lp). In both SW and FW bladders a large portion of the serosal-to-mucosal ion movement appears to be through nonconductive pathways.

Inhibition of N-glycosylation affects transepithelial Na+ but not Na+-K+-ATPase transport

1989 ◽  
Vol 256 (5) ◽  
pp. C958-C966 ◽  
Author(s):  
D. Zamofing ◽  
B. C. Rossier ◽  
K. Geering
Keyword(s):  
Cell Surface ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Beta Subunit ◽  
Beta Subunits ◽  
Toad Urinary Bladder ◽  
Na Transport ◽  
Atpase Inhibition ◽  
Dose Dependent

Tunicamycin (TM) was used in toad urinary bladder (TBM) cells to study the role of N-glycosylation of the beta-subunit of Na+-K+-ATPase. Inhibition of the beta-subunit core glycosylation was dose dependent and coincided with a specific 70% decrease in newly synthesized beta- and alpha-subunits. Na+-K+-ATPase activity paralleled the decrease in the cellular content of the alpha-subunit, although the cellular and cell surface-expressed Na+-K+-ATPase pool was progressively filled up with nonglycosylated beta-subunits. In addition, the decrease in maximal Na+ transport capacity of the Na+-K+-ATPase as assessed by short-circuit current (SCC) measurements in the presence of amphotericin B correlated with the decrease in the total cell surface-expressed beta-subunit population despite the fact that it was composed of 47% nonglycosylated beta-subunits after 42 h of TM treatment. These results are consistent with the interpretation that beta-subunit glycosylation is not important either for the enzyme's intracellular sorting to the plasma membrane or its hydrolytic and transport properties. Finally, TM produced effects on basal SCC and electrical resistance that differed in their times of onset and time periods needed for recovery. Thus, in addition to the Na+-K+-ATPase, other glycoproteins in the apical membrane and the tight junctions must be implicated in the maintenance of transepithelial Na+ transport.

Complex response of epithelial cells to inhibition of Na+ transport by amiloride

1988 ◽  
Vol 254 (2) ◽  
pp. C297-C303 ◽  
Author(s):  
R. S. Fisher ◽  
J. W. Lockard
Keyword(s):  
Urinary Bladder ◽  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Second Phase ◽  
Toad Urinary Bladder ◽  
Apical Surface ◽  
Na Transport ◽  
Transport Inhibition

When toad urinary bladder or frog skin epithelia are treated with amiloride, short-circuit current (Isc), which represents the net active transepithelial Na+ transport rate from the apical to basolateral surface, decreases rapidly (2-5 s) to approximately 15-20% of control values and then slowly, over several minutes, continues falling toward zero. The contribution of this second phase of the decline is dependent on the transporting condition of the tissue before administration of amiloride. Attenuation of the second phase was observed if tissues were subjected to a period of transport inhibition. Tissues preincubated in 0 Na+ Ringer solution on the apical surface were returned to control Na+ Ringer, which caused an approximately 25% increase of Isc above control values. Immediate reapplication of amiloride caused Isc to decrease more rapidly than the previous exposure to values near zero, substantially reducing or eliminating the secondary slow decline. After long-term reincubation of tissues in control, 100 mM Na+ solution, another treatment with amiloride indicated that the magnitude of the secondary decline increased in frog skin but not in urinary bladder epithelia. We conclude that the effect of amiloride is complex and may cause additional effects besides simply blocking entry of Na+ into the apical membrane channel, and we suggest that regulatory mechanisms may be invoked in response to transport inhibition.

Control of ion transport by Gillichthys mirabilis urinary bladder

1983 ◽  
Vol 245 (1) ◽  
pp. R45-R52
Author(s):  
C. A. Loretz ◽  
H. A. Bern
Keyword(s):  
Urinary Bladder ◽  
Transport Mechanism ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Transport ◽  
Nacl Transport ◽  
Cell Region ◽  
Gillichthys Mirabilis ◽  
Ovine Prolactin ◽  
Bladder Urine

The columnar epithelial cell region of the goby Gillichthys mirabilis urinary bladder is the region responsible for active Na and Cl reabsorption from bladder urine. In 5% seawater-adapted fish, reabsorption occurs via an electrically silent coupled NaCl transport mechanism. Bladder reabsorption is increased in seawater-adapted fish above that observed in 5% seawater-adapted fish; incremental reabsorption results from an electrogenic Na transport in addition to the neutral component. Hypophysectomy of seawater-adapted fish reduces the electrogenic Na transport (measured as short-circuit current, ISC) and increases the transepithelial resistance (R) to values near those of 5% seawater-adapted fish. Cortisol restores the ISC and R to normal seawater-adapted values and will initiate electrogenic Na transport in 5% seawater-adapted fish. Ovine prolactin will also restore the ISC and R of columnar cell regions of hypophysectomized seawater-adapted fish to normal seawater-adapted levels; this effect appears to be due to contamination or to inherent stimulatory activity of the ovine prolactin preparation, since endogenous prolactin is ineffective in the restoration of ISC or R.

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