Role of prostaglandin E (PGE) in the modulation of the action of vasopressin on water flow in the urinary bladder of the toad and mammalian kidney

Vasopressin stimulated water flow across renal epithelia is thought to occur through a V2 receptor coupled to adenylcyclase. The increase in water flow occurs as a result of a fusion of water channels with the apical membrane and is indicative of an increase in membrane capacitance following hormone addition.What controls the cycling of water channels and their insertion into the membrane is uncertain. Our laboratory has demonstrated that renal epithelia as well as amphibian urinary bladder membranes, contain a vasopressin V1 receptor which upon activation results in the breakdown of phosphoinositide and the formation of inositol triphosphate and diacylglycerol, the latter an activator of protein kinase C (PKC). The initiation of transepithelial water flow also appears to involve V1 receptors and possibly activation of PKC. To test this hypothesis, we have been using activators of PKC, such as phorbol esters and mezerein, as pharmacological tools to determine if PKC activation results in similar physiological responses as the hormone. Several PKC isozymes, upon activation, are known to be translocated to the apical membrane as visualized by FITC immunofluorescence. Previously, we reported co-localization of PKC subtypes I (γ) and II (β) in toad urinary bladders using monoclonal antibodies and protein A-gold probes. This report includes the localization of PKC subtype III (α) and its distribution pattern using immunogold labeling.

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Vasopressin-stimulated water flow is decreased by thromboxane synthesis inhibition or antagonism

AJP Renal Physiology ◽

10.1152/ajprenal.1980.239.2.f160 ◽

1980 ◽

Vol 239 (2) ◽

pp. F160-F166

Author(s):

R. M. Burch ◽

D. R. Knapp ◽

P. V. Halushka

Keyword(s):

Urinary Bladder ◽

Water Flow ◽

Time Course ◽

Arachidonic Acid Metabolism ◽

Prostaglandin E ◽

Toad Urinary Bladder ◽

Thromboxane Synthetase ◽

Positive Modulator ◽

Dose Dependent Fashion ◽

Dose Dependent

The time course of vasopressin stimulation of water flow and immunoreactive thromboxane B2 (iTXB2) and prostaglandin E (iPGE) biosynthesis was studied in the isolated toad urinary bladder. Vasopressin (25 mU/ml) significantly stimulated iTXB2 synthesis within 8 min, synthesis reaching a maximum rate by 17 min. iPGE synthesis was significantly stimulated within 8 min, remaining unchanged for 24 min. Maximum vasopressin-stimulated water flow was reached between 16 and 24 min. 7-(1-Imidazolyl)-heptanoic acid (7IHA), a thromboxane synthetase inhibitor, inhibited both vasopressin-stimulated water flow and iTXB2 synthesis in a dose-dependent fashion, but did not affect iPGE synthesis. Vasopressin-stimulated water flow and iTXB2 synthesis were significantly correlated (r = 0.75, n = 24, P less than 0.001). 13-Azaprostanoic acid (13APA), a thromboxane antagonist, inhibited vasopressin-stimulated water flow in a dose-dependent fashion. Inhibition of arachidonic acid metabolism abolished the effects of 7IHA and 13APA on vasopressin-stimulated water flow. 7IHA and 13APA had no effect on cAMP-stimulated water flow. These results confirm that vasopressin stimulates TXA2 and PGE synthesis and support the hypothesis that TXA2 is a positive modulator of vasopressin-stimulated water flow in the toad urinary bladder.

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Blockade of colchicine-induced inhibition of vasopressin-stimulated osmotic water flow: failure to influence microtubule formation

AJP Renal Physiology ◽

10.1152/ajprenal.1985.249.4.f464 ◽

1985 ◽

Vol 249 (4) ◽

pp. F464-F469

Author(s):

D. A. Baron ◽

R. M. Burch ◽

P. V. Halushka ◽

S. S. Spicer

Keyword(s):

Urinary Bladder ◽

Water Flow ◽

Volume Fraction ◽

Cyclooxygenase Inhibitors ◽

Maximal Response ◽

Prostaglandin E ◽

Toad Urinary Bladder ◽

Meclofenamic Acid ◽

Osmotic Water ◽

Osmotic Water Flow

Colchicine inhibits vasopressin-induced osmotic water flow across isolated toad urinary bladder. Concomitantly, colchicine has been shown to reduce the relative cytoplasmic volume fraction of microtubules in the apical granular cells of this epithelium that have been shown previously to mediate the hydroosmotic effect of vasopressin. Therefore, an intact cytoskeleton has been postulated to be a requirement for a full response to vasopressin. Since it has been demonstrated recently that cyclooxygenase inhibitors (meclofenamic acid) abrogate the inhibition by colchicine of vasopressin-stimulated water flow, we tested by stereological criteria the hypothesis that colchicine in the presence of meclofenamic acid does not prevent the polymerization of tubulin. Our results show that the relative cytoplasmic volume fraction of microtubules was reduced 75% by colchicine in the presence or absence of meclofenamic acid. An alternative explanation of the inhibitory action of colchicine is its ability in the toad urinary bladder to enhance the endogenous synthesis of and sensitivity to prostaglandin E, a potent negative modulator of vasopressin-stimulated water flow. An intact microtubular component of the cytoskeleton does not appear to be required for a maximal response to a physiological dose of vasopressin.

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Inhibition of vasopressin-stimulated prostaglandin E biosynthesis by chlorpropamide in the toad urinary bladder. Mechanism of enhancement of vasopressin-stimulated water flow.

Journal of Clinical Investigation ◽

10.1172/jci108894 ◽

1977 ◽

Vol 60 (6) ◽

pp. 1348-1353 ◽

Cited By ~ 35

Author(s):

R M Zusman ◽

H R Keiser ◽

J S Handler

Keyword(s):

Urinary Bladder ◽

Water Flow ◽

Prostaglandin E ◽

Toad Urinary Bladder

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Effect of verapamil on cytoplasmic distribution of granules and microfilaments in amphibian urinary bladder

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103681 ◽

1988 ◽

Vol 46 ◽

pp. 324-325

Author(s):

A.J. Mia ◽

L.X. Oakford ◽

T. Yorio

Keyword(s):

Urinary Bladder ◽

Water Flow ◽

Morphological Changes ◽

Granular Cell ◽

Cytosolic Calcium ◽

Calcium Storage ◽

Amphibian Urinary Bladder ◽

Vesicular Membrane ◽

High Concentrations ◽

Cytoskeletal System

The amphibian urinary bladder has been used as a ‘model’ system for studies of the mechanism of action of antidiuretic hormone (ADH) in stimulating transepithelial water flow. The increase in water permeability is accompanied by morphological changes that include the stimulation of apical microvilli, mobilization of microtubules and microfilaments and vesicular membrane fusion events . It has been shown that alterations in the cytosolic calcium concentrations can inhibit ADH transmembrane water flow and induce alterations in the epithelial cell cytomorphology, including the cytoskeletal system . Recently, the subapical granules of the granular cell in the amphibian urinary bladder have been shown to contain high concentrations of calcium, and it was suggested that these cytoplasmic constituents may act as calcium storage sites for intracellular calcium homeostasis. The present study utilizes the calcium antagonist, verapamil, to examine the effect of calcium deprivation on the cytomorphological features of epithelial cells from amphibian urinary bladder, with particular emphasis on subapical granule and microfilament distribution.

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