Quantitative analysis of exocytosis and endocytosis in the hydroosmotic response of toad bladder

Abstract

This study concerns the timing and magnitude of exocytosis and endocytosis in the granular cells of toad bladder during the hydroosmotic response to antidiuretic hormone. Granule exocytosis at the luminal cell surface is extensive within 5 min of the administration of a physiological dose of hormone. Hydroosmosis becomes detectable during this time period. The amount of membrane added to the luminal surface by exocytosis during 60 min of exposure to hormone can be of the same order of magnitude as the extent of the luminal plasma membrane. Endocytosis, demonstrated by peroxidase uptake from the luminal surface, becomes extensive during the period 15-45 min after hormone administration. Thus, maximal endocytic activity occurs later than the period of most extensive exocytosis and seems to correlate with the onset of the decline in water movement. The amount of membrane retrieved from the luminal surface by endocytosis during 60 min of stimulation is at least three quarters of that added by exocytosis. The bulk membrane movement in ADH stimulated preparations does not require the presence of an osmotic gradient. Colchicine inhibits the hydroosmotic response, the exocytosis of granules, and endocytosis at the luminal surface. These results strengthen our view that the bulk circulation of membrane at the cell surface, via exocytosis and endocytosis, is closely related to the permeability changes occurring at the surface.

Transcellular water flow modulates water channel exocytosis and endocytosis in kidney collecting tubule.

“…The impetus for this study was the observations in toad urinary bladder that a serosal-to-mucosal osmotic gradient stimulated membrane retrieval (20,22). Based on the toad bladder data and the collecting tubule data reported here, we proposed that water flow itself might provide a physical force to influence the targeted movement ofmembranes within a cell.…”

“…The interesting observation has been made in a number of laboratories that the presence of a serosal-to-mucosal osmotic gradient (serosal > mucosal osmolality) appears to alter the endocytic phase of membrane cycling in toad urinary bladder (20)(21)(22). A serosal-to-mucosal osmotic gradient both increases the endocytic retrieval of fluid-phase fluorescent markers, and enhances the downregulation ofwater permeability in response to prolonged vasopressin stimulation.…”

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

“…In the absence of ADH stimulation, granular cells internalize fluid-phase markers from their apical surface at an extremely low rate. During ADH stimulation in the absence of an osmotic gradient across the bladder, there is minimal endocytosis of apical extracellular markers (26,30,34). In contrast, high rates of osmotic water flow and the removal of ADH cause the concerted endocytosis of aggregate-containing membrane (10) and a related decrease in water permeability (9,26).…”

Effect of nocodazole on the water permeability response to vasopressin in rabbit collecting tubules perfused in vitro.

“…colchicine, nocodazole) inhibit the development of the hydrosmotic response to vasopressin or exogenous cyclic AMP (Taylor Mamelak, Golbetz & Maffly, 1978;Brady, Parsons & Coluccio, 1981). Such agents also interfere with the hormone-induced increase in apical membrane area (Gronowicz et al 1980;Palmer & Lorenzen, 1983), and with the appearance of the particle aggregates in the apical plasma membrane (Kachadorian, Ellis & Muller, 1979). The available data are consistent with the view that microtubules in the apical cytoplasm are involved in the translocation of the aggregate-containing vesicles towards the apical surface of the granular cells, prior to their exocytotic insertion into the apical plasma membrane (Kachadorian et al 1979;Muller et al 1980;reviewed in Pearl & Taylor, 1985).…”