Membrane structural specialization of the toad urinary bladder revealed by the freeze-fracture technique

Abstract

Examination of the toad urinary bladder by freeze-fracture electron microscopy reveals intramembrane particle arrays at a number of membrane sites. An array in which particles are aggregated into closely apposed parallel rows is found in the granular cell luminal membrane of dehydrated toads fixed in situ. These aggregates are structurally indistinguishable from those previously associated with vasopressin exposure in vitro. Aggregates are not found in granular cell luminal membrane in the case of hydrated toads fixed in situ. However, structurally similar arrays are found at low frequency in the membrane of cytoplasmic vacuoles in granular cells and in the plasma membrane of basal cells in both hydrated and dehydrated toads. Aggregates are also present at these sites in control and vasopressin-treated bladders from in vitro experiments. Particle arrays characteristic of gap junctions, desmosomes and hemidesmosomes also occur in the plasma membrane of basal cells. In addition, distinctive square arrays of particles exist in the plasma membrane of the bladder's mesothelium. Although a variety of intramembrane particle arrays exist in the toad urinary bladder, only the occurrence of organized particle aggregates in the luminal membrane of granular cells appears to be associated with vasopressin exposure.

Freeze‐fracture observations on human fetal kidney in serum‐free organ culture

“…Their rod-shaped particles were shown in rotary shadowed replicas to be composed of two individual particles in close apposition (Friend, 1986). The presence of elongated particles on these cells has been reported in collecting tubules of many animal species (Brown, 1978;Ridderstrale et al, 1988), as well as in different transporting epithelia such as amphibian urinary bladder and skin (Rosen, 1972;Wade, 1976;Brown and Orci, 1988), rat epididymis (Brown and Montesano, 1980), hen intestine (Eldrup et al, (1980), and monkey colon (Neutra, 1979). These cells are believed to be involved with urinary acidification, bicarbonate secretion, and potassium reabsorption (Stetson et al, 1980;Brown and Orci, 1988).…”

Morphology of the Nephron in the Mesonephros of Bufo bufo (Amphibia, Anura, Bufonidae)

“…The results presented in the present study of the nephron of B. bufo make a precise dissection of desired nephron fragments possible. Corresponding to the amphibian's other osmoregulatory epithelia, cells identical to the intercalated (mitochondria-rich) cells of the late distal tubule and collecting tubule have been found in the skin and urinary bladder (Choi, 1963;Budtz & Larsen 1973Wade 1975;Whitear 1975). and their function in the skin has been associated with osmoregulation (Larsen 1991;Larsen er al.…”

Identification of specific apical membrane polypeptides associated with the antidiuretic hormone-elicited water permeability increase in the toad urinary bladder.

“…Under basal conditions, the apical cytoplasm of granular cells contains tubularshaped vesicles that have been named "aggrephores" because on freeze-fracture electron microscopy they contain distinctive particle aggregates within their limiting membranes (3)(4)(5). Aggrephores store and shuttle particle aggregates into and out of the apical plasma membrane in response to changes in the concentration of ADH (6).…”

“…Aggrephores store and shuttle particle aggregates into and out of the apical plasma membrane in response to changes in the concentration of ADH (6). In response to ADH, aggrephores fuse with the apical plasma membrane and the plasma membrane becomes enriched in particle aggregates (4)(5)(6)(7)(8). When ADH is withdrawn, particle aggregates and aggrephores are retrieved from the apical membrane (9,10), and the water permeability response reverses.…”