The penetration of water into the epithelium of toad urinary bladder and its modification by oxytocin

Abstract

Summary.A new method was devised to study the movement of water across the toad urinary bladder. The uptake of tritiated water (THO) into the tissue and serosal fluid of everted bladder sacs was compared with the appearance, over very short time periods (5 to 40 sec), of THO in the serosal fluid alone. The results showed that under basal conditions no significant difference could be detected between the specific radioactivity in the serosal fluid and the specific radioactivity in the tissue. In the presence of oxytocin the specific radioactivity in the bladder tissue in 5 sec was about 10 times the specific radioactivity present in the serosal fluid. The accumulation of tritiated water in the tissue under the action of oxytocin suggests the existence of a second barrier to water movement other than the luminal border. While the overall increase in permeability of the bladder wall by oxytocin is only about twice the control value, the increase in water uptake by the tissue is much higher. It is concluded that the increase in diffusion of water induced by oxytocin across the luminal border of the cells has been largely underestimated by previous determinations and would be large enough to explain the observed osmotic flux in similar conditions. It was also observed that the permeability of the bladder to water was a function of the tonicity of the mucosal solution.The permeability of different biological membranes to water has been extensively studied, by determining both unidirectional and net fluxes across the membrane. A discrepancy between the experimentally observed rate of net water movement and the one predicted from the rate of tritiated water (THO) diffusion has been observed. In the case of toad urinary bladder, the total osmotic water flow is six times larger than expected (Hays & Leaf, 1962). The reliability of the observation of the difference between osmotic and diffusional permeability has been questioned. Dainty & House (1966a, b) have reported that the presence of unstirred layers could * Career investigator from the "Consejo Nacional de Investigaciones Cientfficas y T6cnicas" (CONICET), Argentina.

Effect of antidiuretic hormone on water and solute permeation, and the activation energies for these processes, in mammalian cortical collecting tubules

“…Clearly, the latter data are in close accord with the ADH-dependent values of Pr and PDw in rabbit cortical collecting tubules. Moreover, Parisi and Piccinni [36] have provided direct evidence for significant hindrances to water diffusion within the epithelial cell layer of toad urinary bladder. Thus it could be argued that, in anuran epithelia as well as in mammalian cortical collecting tubules, ADH-mediated water transport in luminal (or apical) plasma membranes is diffusional [21].…”

Histochemical and elemental localization of calcium in the granular cell subapical granules of the amphibian urinary bladder epithelium

“…It is this epithelium that represents the major permeability barrier to water (Leaf, 1967;Parisi and Piccinni, 1973). The epithelium is comprised of four cell types: 1) granular cells, 2) mitochondria-rich (MR) cells, 3) goblet cells, and 4) basal cells (Peachey and Rasmussen, 1961).…”

Urea uptake and translocation in toad urinary bladder: The effect of antidiuretic hormone

“…The method employed allowed us to study the time course of urea uptake and distribu- . The water results were taken from Parisi & Piccinni (1973) tion and, in this case, to compare these results with those obtained when working on water uptake and distribution (Parisi & Piccinni, 1973). The present results indicate that the mucosal border of the epithelial bladder cells is the only effective barrier for urea movement in the different conditions here studied.…”

“…If this is true, the barrier must be the mucosal border in both cases. This is not the case when tritiated water is moving through the same tissue (Parisi & Piccinni, 1973). Means_+ SEM.,…”

“…These values are compared with the results obtained when studying water movement, specially under the action of the hormone. In a previous work the penetration and distribution of tritiated water into the toad urinary bladder has been studied (Parisi & Piccinni, 1973), following the uptake and translocation of the tracer over short time periods. We used the same approach here when studing urea permeation.…”