Effect of acetylcholine on the pituitrin induced osmotic flow of water through the wall of the frog urinary bladder]

The role of intercellular pathways in the ADH-dependent water transport was studied on the frog urinary bladder by means of acetylcholine (AC) and other cholinergic compounds. AC (10(-3) M) was found to cause a strong suppression of the pituitrin-stimulated water flow. Analogous effect was produced by AC on the osmotic flow stimulated by cyclic adenosine monophosphate (cAMP) and theolin. The antipituitrin effect was not reproduced either by nicotine, nor by potent M-cholinomimetic agents (methylfurmetide and F-2268), and was not prevented by M- and N-cholynolytic drugs (atropine, metacin, flaxedil, hexamethonium). However, the antipituitrin effect of AC was completely removed by the anticholinesterase drugs with different mode of action (eserine, proserine, armin, acridine iodmethylate, GD-42) in concentrations of 10(-6)--10(-3) M. It was concluded that the smooth muscles contraction with the subsequent closure of the intercellular spaces was not responsible for the antipituitrinic action of AC. This effect appears to be connected with cholinesterase activation. A possible role of the phosphoinositides in the water permeability regulation of the urinary bladder wall is discussed.     

Effect of colchicine on the osmotic water flow across the toad urinary bladder

Osmotic water movement across the toad urinary bladder in response to both vasopressin and cyclic AMP was inhibited by 10^?5 to 10^?4 M colchicine on the serosal but not on the mucosal side. This inhibitory effect was found to be time- and dose-dependent. Colchicine alone did not change basal osmotic flow and a baseline of the short-circuit current (I_sc) and also did not affect a vasopressin-induced rise of the I_sc. The inhibitory effect was not prevented by the addition of pyruvate. The osmotic water movement produced by 360 mM Urea (mucosal), 360 mM mannitol (serosal) or 2 μg/ml amphotericin B (mucosal), was not affected by 10^?4 M colchicine. These results suggest that colchicine inhibits some biological process subsequent to the formation of cyclic AMP except a directional cytoplasmic streaming process where microtubules may be involved.     

Effect of distension on ADH-induced osmotic water flow in toad urinary bladder

Summary We recently described a method by which the resistance to water flow of the luminal membrane of ADH-stimulated toad bladder can be quantitatively distinguished from that of barriers lying in series with it. This method requires estimates of both total bladder water permeability (assessed by transbladder osmotic water flow at constant gradient) and luminal membrane water permeability (assessed by quantitation of the frequency of ADH-induced luminal membrane particle aggregates). In the present study we examined the effect of bladder distension on transepithelial osmotic water flow before and during maximal ADH stimulation. Base-line water flow was unaffected by bladder distension, but hormonally stimulated flow increased systematically as bladders became more distended. Distension had no effect on the frequency of ADH-induced intramembranous particle aggregates. By comparing the relationships between aggregate frequency and hormonally induced water permeability in distended and undistended bladders, we found that distension appeared to enhance ADH-stimulated water flow by decreasing the resistance of the series permeability barrier while the apparent water permeability associated with each single luminal membrane aggregate was unaffected. In that bladder distension causes tissue thinning, the series resistance limiting ADH-stimulated water flow appears to be accounted for by deformable barriers within the bladder tissue itself, probably unstirred layers of water.     

Effect of colchicine on the osmotic water flow across the toad urinary bladder.

Osmotic water movement across the toad urinary bladder in response to both vasopressin and cyclic AMP was inhibited by 10(-5) to 10(-4) M colchicine on the serosal but not on the mucosal side. This inhibitory effect was found to be time- and dose-dependent. Colchicine alone did not change basal osmotic flow and a baseline of the short-circuit current (Isc) and also did not affect a vasopressin-induced rise of the Isc. The inhibitory effect was not prevented by the addition of pyruvate. The osmotic water movement produced by 360 mM Urea (mucosal), 360 mM mannitol (serosal) or 2 mug/ml amphotericin B (mucosal), was not affected by 10(-4) M colchicine. These results suggest that colchicine inhibits some biological process subsequent to the formation of cyclic AMP except a directional cytoplasmic streaming process where microtubules may be involved.     

Metabolic dependence of the offset of antidiuretic hormone-induced osmotic flow of water across the toad urinary bladder

Summary The elevated osmotic permeability to water induced by antidiuretic hormone (ADH) in the isolated urinary bladder of the toad is rapidly reversed by removal or washout of the ADH. This return to normal water permeability is delayed by the suppression of production of metabolic energy by any of three maneuvers: (i) low temperature (2°C); (ii) inhibition of oxidative phosphorylation (10mm azide or 0.5mm 2,4 dinitrophenol); or (iii) inhibition of glycolysis (10mm iodoacetate or 10mm 2-deoxyglucose). Moreover, exposure to cytochalasin B, 2.1×10^–5 m, either before or after initiation of the hormonal effect also delays the return of water permeability to normal following removal of ADH. When considered within constraints imposed by models which predict ADH's action on water permeability to be either via modulation of the fluidity of lipids in the membrane or via the figuration of proteins (pores) in the lipid membrane, these observations on the inhibition of the reversal of ADH stimulation of water flow are more consistent with the protein (pore) theory and place limitations on the mechanisms by which proteins in such pores can return to the resting or impermeable state.     

Effect of monensin on osmotic water flow across the toad bladder and its stimulation by vasopressin and cyclic AMP

Summary The effects of the sodium ionophore monensin on osmotic water flow across the urinary bladder of the toadBufo marinus were studied. Monensin alone did not alter osmotic water flow; however, the ionophore inhibited the hydrosmotic response to vasopressin and cyclic AMP in a dose-dependent manner. The inhibitory effects of monensin were apparent when the ionophore was added to the serosal bathing solution but not when it was added to the mucosal bathing solution. The inhibitory effect of serosal monensin required the presence of sodium in the serosal bathing solution but not the presence of calcium in the bathing solutions. Thus, it appears that intracellular sodium concentration is a regulator of the magnitude of the hydrosmotic response to vasopressin and cyclic AMP.     

Effect of monensin on osmotic water flow across the toad bladder and its stimulation by vasopressin and cyclic AMP

The effects of the sodium ionophore monensin on osmotic water flow across the urinary bladder of the toad Bufo marinus were studied. Monensin alone did not alter osmotic water flow; however, the ionophore inhibited the hydrosmotic response to vasopressin and cyclic AMP in a dose-dependent manner. The inhibitory effects of monensin were apparent when the ionophore was added to th serosal bathing solution but not when it was added to the mucosal bathing solution. The inhibitory effect of serosal monensin required the presence of sodium in the serosal bathing solution but not the presence of calcium in the bathing solutions. Thus, it appears that intracellular sodium concentration is a regulator of the magnitude of the hydrosmotic response to vasopressin and cyclic AMP.     

Barriers to water flow in vasopressin-treated toad urinary bladder

Summary Unstirred layers of water complicate the measurement of water permeability across epithelia. In the toad urinary bladder, the hormone vasopressin increases the osmotic water permeability of the granular epithelial cell's luminal membrane, and also leads to the appearance of aggregates of particles within this membrane. The aggregates appear to be markers for luminal membrane osmotic water permeability. This report analyzes the relationship between transbladder osmotic water flow and aggregate frequency, and demonstrates that flow across the bladder is significantly attenuated by unstirred layers of water or by structural barriers other than the luminal membrane when the luminal membrane is made permeable by vasopressin. This analysis in addition yields unique values for the permeabilities of both the luminal membrane and the barriers to water flow which lie in series with it.     

Localization of barriers to water flow in toad urinary bladder

Although it is well accepted that vasopressin (ADH) increases the permeability to water of the toad bladder granular cell's luminal membrane, recent studies have suggested that regulation also takes place at an additional "postluminal" site within the epithelial granular cell. These studies are based upon the observation that a number of experimental maneuvers can alter tissue permeability to water, but do not change the number of particle aggregates observed on the protoplasmic face of the granular cell's luminal membrane with freeze-fracture electron microscopy. These aggregates are believed by many investigators to mediate the transport of water across the luminal membrane. The dissociation between permeability and aggregate frequency described above has been variously interpreted as the consequence of changes in the permeability of the aggregates themselves, or of changes in the permeability of a "postluminal" barrier that is functionally in series with the luminal membrane. We attempted to distinguish between these 2 possibilities by studying paired toad bladders during 3 protocols that alter vasopressin-stimulated water flow across the intact tissue without altering aggregate frequency. Estimates of the permeability of postluminal barriers were obtained by exposing the luminal surface to amphotericin B, an antibiotic that forms water-permeant channels in the luminal membrane. Of the 3 protocols, only diminishing bladder filling volume decreased the water flow elicited by luminal amphotericin B, suggesting that only that protocol indeed decreased the permeability of some postluminal barrier. The other 2 protocols, increasing PCO2 and repeatedly stimulating the bladder with vasopressin, did not alter amphotericin B-elicited flow, suggesting that postluminal barriers were not altered by these 2 protocols.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulative effect of guanylylimidodiphosphate on the vasopressin-induced increment of osmotic water flow of the toad bladder.

The effect of guanylylimidodiphosphate [Gpp(NH)p] on vasopressin-induced osmotic water flow across the bladder of the toad, $\text{Bufo}\text{bufo}\text{japonicus}$ was examined. Gpp(NH)p significantly enhanced vasopressin-induced osmotic water flow of the bladder at a concentration of 1 × 10^?5M, while it showed no effect on the water flow without vasopressin. Gpp(NH)p alone could not enhance cyclic AMP-induced osmotic water flow of the toad bladder. Adenylylimidodiphosphate [App(NH)p] could not enhance vasopressin-induced osmotic water flow of the bladder at a concentration of 1 × 10^?5M. The results suggest that Gpp(NH)p can enhance the physiological effect of vasopressin by stimulating vasopressin activation of adenylate cyclase during substrate and hormone depletion of the toad bladder.     

Linear free energy relationship for osmotic water flow through a membrane

A linear free-energy relationship has been found for the osmotic water flux through membranes in a broad variety of systems including electrolytes, organic compounds, intact biological cells and industrial scale filtration. In all cases, broad concentration ranges were found in which the equation In v = In m + β (v. flux (in kg cm⁻² min⁻¹: m. molarity)) was valid. The parameters and β were interpreted in terms of molecular weight, mean ionic radius, enthalpy of solvation. electronic structure and H-bonding propensity. The equation is independent of the membrane material and of the presence of other solutes and precipitates, as long as the latter are incompressible. Its parameters are only slightly dependent upon the temperature. The contributions from different solutes to the osmotic flux are at appreciable concentrations even additive. The relationship permits the prediction of the osmotic water flux and of the rate of filtration of systems of known composition. For simple systems it permits determination of the molecular weight, mean ionic radius, degree of hydration and enthalpy of solvalion. It is suggested that osmosis is primarily due to the shift of hydration equilibria and that guanidine hydrochloride. in a realistic concentration range, forms practically infinite clathrates with water. The properties of the urea and Gdn.HCl systems indicate that these solutes either reversibly change the membrane structure and/or display intrinsic hysteresis.     

Regulation of luminal membrane water permeability by water flow in toad urinary bladder

Intramembranous particle aggregates (presumed sites for water flow) which appear in the luminal membrane consequent to ADH treatment are derived from cytoplasmic membrane structures (now termed "aggrephores") which fuse with the luminal membrane. We have previously shown that bladders stimulated in the absence of an osmotic gradient have about twice as many aggregates and about three times as many sites of aggrephore fusion as bladders stimulated with ADH in the presence of a 175 milliosmolal gradient. The present studies show that the frequency of fused aggrephores and luminal membrane aggregates can be modified as a consequence of alterations in transmembrane water flow initiated by changing the transbladder osmotic gradient during hormone stimulation. Bladders treated with ADH for 1 hr without a gradient and then for 1 hr with a gradient had approximately 1/3 as many aggregates and fusion sites as paired bladders treated for 2 hr without a gradient. Conversely, bladders treated with ADH for 1 hr with a gradient and then for 1 hr without a gradient had approximately 2x as many aggregates and fusion sites as bladders treated for 2 hr with a gradient. In other experiments we demonstrate that the time course of hormone washout is greatly accelerated if carried out in the presence of an osmotic gradient. In paired bladders that were first stimulated with ADH for 30 min in the absence of a gradient, aggregates and fusion sites as well as osmotic water permeability determined in fixed bladders, persisted at near maximum levels for 15 min of washout in the absence of a gradient.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of acid-base changes on vasopressin-stimulated water flow in toad urinary bladder

Water flow was measured gravimetrically in the presence and absence of vasopressin across the toad urinary bladder. Four groups of toads in different states of acid-base balance were used; a normal group, a group in NH₄Cl induced metabolic acidosis, respiratory acidosis, and a group in NaHCO₃ induced metabolic alkalosis. Vasopressin induced water flow was significantly reduced during metabolic acidosis and respiratory acidosis. Metabolic alkalosis had no effect on the hydro-osmotic response to vasopressin. Dibutyryl cyclic-AMP-stimulated water flow on the other hand was not affected by either a metabolic or respiratory acidosis. Treatment with indomethacin was able to reverse the observed reduction in the vasopressin-stimulated water flow response in the toad bladder during metabolic and respiratory acidosis. We conclude that the vasopressin stimulated water flow is altered during acidosis and evidence suggests that prostaglandins may be involved in the observed reduction in vasopressin-stimulated water flow.