ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00419.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00423.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

It is now generally accepted that ADH‐induced increase in water permeability in responsive epithelia is associated with the insertion of specific structures in the apical membrane of epithelial cells. Up to now, these structures have only been recognized in freeze‐fractured preparations and their chemical nature is still unknown. In this study, we used the label‐fracture method (Pinto da Silva and Kan, J. Cell Biol., 99, 1156‐1161, 1984) to investigate the distribution of wheat germ agglutinin (WGA) on the luminal plasma membrane of freeze‐fractured frog urinary bladder epithelial cells. With label‐fracture, the cytochemical markers are seen superimposed with the conventional high resolution image of the E face. Label‐fracture of tissue treated for 15 min with WGA and subsequently labeled with colloidal gold coated with ovomucoid showed uniform distribution of gold particles along the exoplasmic fracture face. Stereomicrographs show that the gold label is under the fracture face as it is attached to the outer surface of the membrane. Preincubation of the bladder with WGA for 3 hr induced a segregation of the intramembranous particles of the apical plasma membrane. In this condition, we observed a co‐distribution of WGA‐gold complexes with the segregated particles on the E face. This indicates that WGA‐binding sites are located on glycoproteins which probably comprise the large intramembranous particles dispersed on the exoplasmic faces of freeze‐fractured luminal membranes. In contrast, the numerous small intramembrane particles observed on P faces remained evenly distributed even after exposure to WGA and are, therefore, unrelated to WGA receptor sites. After WGA treatment, ADH still induced the formation of aggregates inside the smooth domains. A few WGA‐binding sites appeared to be associa

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00424.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The apical plasma membrane of epithelial cells of frog and toad urinary bladder is subject to large modifications during the induction of water permeability by the antidiuretic hormone. A better characterization of the apical membrane is necessary for a clear understanding of the mechanisms of hormone action. Towards this end, apical material was extracted by enzymatic treatment and by incubation with detergent. Proteolytic enzyme alone had little effect under our conditions. A pretreatment with several glycosidases (alpha‐mannosidase or endo‐beta‐N‐acetylglucosaminidase H) increased the hydrolytic action of papain, elastase, proteinase K or Staphylococcus aureus V8 protease and allowed the detection of a major 76 kD in SDS gel electrophoresis. The n‐octyl‐beta‐D‐glucopyranoside (0.2%) led to the extraction after 150 mn of 1 to 5 micrograms proteins per cm2 of amphibian urinary bladder apical surface. The extracted proteins migrated as several bands on SDS gels. One of them probably corresponds to the 76 kD fragment obtained after proteolysis. The absence of alteration of the water permeability after extraction and the good preservation of the ultrastructure are evidence for the localisation of the 76 kD at the apical membrane surface. This protein may be the best candidate as antigen to raise antibodies against the apical surface of amphibian urinary bladder e

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00425.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The A23187 calcium ionophore strongly inhibits the hydrosmotic response to vasopressin. On the contrary neither exogenous cAMP nor theophylline‐induced hydrosmotic response are affected by Ca++‐ionophore. The effects obtained with A23187 suggest that calcium ions modulate vasopressin‐induced osmotic water flow by interfering with a pre‐cAMP step. The increase in intracellular calcium concentration induced by A23187, in fact, may inhibit the rate of cAMP formation by interfering with the vasopressin‐stimulated adenylate cyclase system. This inhibition seems to be restricted to a locus proximal to the catalytic subunit of adenylate cyclase, whereas the hydrosmotic response to forskolin, a non‐hormonal activator, is not affected by calcium ionophore addition. In order to clarify whether calcium ions act directly on the adenylate cyclase system or activate a more complex pathway, we studied the interaction between calcium and prostaglandins in modulating the hydrosmotic response to vasopressin. Direct measurements by radioimmunoassay of PGE2 release in the serosal medium show that A23187 notably increases PGE2 release. Furthermore, the inhibition of prostaglandin biosynthesis by hydrocortisone (a phospholipase inhibitor) or by indomethacin and naproxen (agents that inhibit arachidonic acid oxygenase) results in augmented vasopressin‐stimulated water flow and prevents the inhibitory effect of the ionophore. Collectively these results strongly suggest that the effects obtained with A23187 on hydrosmotic response to ADH, are closely linked to calcium‐stimulated PG

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00426.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

I present a technique that permits evaluation of the permeability to water of the luminal membrane of the toad urinary bladder, independently of constraints to water flow imposed by the remainder of the tissue. This technique essentially depends on fixation of the luminal membrane with 1% glutaraldehyde for 5 min, and subsequent elimination of cytosolic constraints by decreasing the tonicity of the serosal bath to 1/2 normal strength. The increased hydraulic conductivity found with serosal hypotonicity is readily reversible, as the bladder returns to an isotonic serosal bath. By evaluating water flow in luminally fixed bladders during bathing in normal and hypotonic bath, one may identify the relative contribution of the luminal membrane and the “cytosol” on water flow. Using this technique, I found that the effect of the prostaglandin inhibitor Naproxen to increase vasopressin‐stimulated water flow is due to increased luminal membrane permeability. The effect of histidine to increase vasopressin‐stimulated water flow, however, depends on increased permeability of both the luminal membrane as well as the underlying structures. The action of serosal hypertonicity to induce water flow is due to an increased luminal permeability. However, serosal hypertonicity decreases “cytosolic” permeability, so that its overall function is a composite effect of its action at the luminal membrane and the “cyt

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00427.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Antidiuretic hormone (ADH) promotes the fusion of cytoplasmic tubular structures with the luminal membrane of receptor tissues such as toad urinary bladder. To determine whether fusion is a continuous cyclic process, bladders were stimulated with ADH with colloidal gold in the luminal bathing medium. After as little as 15 min of stimulation, gold‐filled tubules were seen in the cytoplasm, evidence that cycling was indeed taking place. Serial sections confirmed that these tubules had no connection with the luminal membrane, and had returned to the cytoplasm. Cessation of ADH stimulation, followed by a second stimulation, greatly reduced the number of gold‐filled cytoplasmic tubules, suggesting that many tubules were capable of refusion. Mean fusion event diameter underwent significant changes, enlarging at 15 min, and contracting at 60 min. Thus, ADH initiates a process of continuous cycling of cytoplasmic tubules between cytoplasm and luminal membr

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00428.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY