Lanthanum inhibition of the action of oxytocin on the water permeability of the frog urinary bladder: Effect on the serosal and the apical membrane

Abstract

Summary. The effect of La 3+ ion on the hydrosmotic response of the frog urinary bladder to oxytocin has been studied. When added to the serosal medium, in the concentration range 10-4M to 10 -3 M, La 3+ inhibits the response to oxytocin, theophylline and cyclic-AMP, but not to hypertonicity. When added to the apical medium at a concentration greater than 5 x 10 -a M, La 3+ exhibits an inhibitory effect only during respective stimulation, either by hormone or by hypertonicity, but has no significant effect on the developed response. The significance of this particular mode of action is discussed in terms of possible electrical potential variations of the apical membrane during stimulation.It is well known that the action of the neurohypophysial hormones on the serosal side of the urinary bladder epithelium results in an increase in the water permeability of the apical membrane of the epithelial cells [5,9,12,13,15]. The mechanism of this action is not understood, although since the work of Handler and Orloff [8,[19][20][21] several of the intraceilular biochemical steps have been elucidated.While the mechanism by which the water permeability of the apical membrane itself is modified is unknown, hypotheses may be made concerning the possible structural transformation underlying the membrane permeability change.It is currently accepted, on the basis of evidence obtained on model systems and on biological membranes [7,23], that calcium plays an important role in maintaining the tight and ordered organization of biological membranes and therefore their low and selective permeability. It may be reasonably assumed that the apical membrane of epithelial ceils has similar

Lanthanum inhibition of Vibrio cholerae and Escherichia coli enterotoxin-induced enterosorption and its effects on intestinal mucosa cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate levels

“…When La3+ exposure occurred more than 30 min after toxin exposure, its effectiveness in inhibiting CE-induced enterosorption was reduced. This is very similar to the effect of this cation on the hydrosmotic response of the frog urinary bladder to antidiuretic hormone (25). When added to the apical medium at concentrations in excess of 5 mM, La3+ inhibited the response to this hormone, provided the hormonal response had not yet fully developed.…”

“…The physiological effects of trivalent cations, such as La3+, are generally attributed to this ion displacing Ca2+ from some site (24,25). We…”

Reversible inhibition by lanthanum of the hydrosmotic response to serosal hypertonicity in toad urinary bladder

“…The results of the present experiments in the isolated toad bladder on water transport are at variance with observations in the isolated frog bladder. In the latter preparation, serosal La 3 § had no effect on either basal water flux or on the hydrosmotic response to SH (Wietzerbin, Lange & Gary-Bobo, 1974). On the other hand, others have reported a stimulating effect of La 3 § on basal water flux in toad skin and bladder which occurred without any increase in cellular cyclic AMP, while La 3 § has also been shown to blunt the hydrosmotic response to ADH and to decrease the ADH-induced increase in cyclic AMP (Wong, Bedwani & Cuthbert, 1972;Marguerat & de Sousa, 1975).…”

Extracellular Ca2+ and the effect of antidiuretic hormone on the water permeability of the toad urinary bladder: An example of flow-induced alteration of flow

“…Since disruption of tight junctions with Ca 2+ removal depends on the use of CaZ+-chelating agents [31,48], we attempted to preserve tissue polarity, using only repetitive washing to remove Ca 2+. The integrity of epithelia in CaZ+-free media was assessed by transepithelial passive permeability to large molecules and by structural studies.…”

“…The treatments were: low serosal pH [22], serosal La 2+ [24,48] and colchicine [25,46]. The treatments were: low serosal pH [22], serosal La 2+ [24,48] and colchicine [25,46].…”