Lack of correlation between transepithelial transport capacity and paracellular pathway ultrastructure in Alcian blue-treated rabbit gallbladders.

Abstract

The effects of mucosal application of 1 mg% Alcian blue (a trivalent cationic phthalocyanine dye) on functional and ultrastructural parameters of the isolated rabbit gallbladder have been studied. Apart from minor changes in the shape of the group of central microvilli observed in thin-section electron microscopy and scanning electron microscopy, the major ultrastructural change induced by Alcian blue was an almost complete collapse of intercellular spaces in the region above the tight junctions up to the bases of the marginal microvilli as revealed by thinsection electron microscopy . Freeze-fracture electron microscopy demonstrated a complete disappearance of intramembrane particles of neighboring cell membranes corresponding to the region of interspace collapse. Transepithelial electrical resistance (RT) increased from 44 .5 to 58.7 ohm-cm' upon treatment with Alcian blue . This increase could be well accounted for by the observed structural changes in the paracellular pathway if this pathway determines the low resistance of the rabbit gallbladder epithelium . Despite the increase in RT, net mucosa-to-serosa fluid transport and the spontaneous mucosa-positive potential difference of 3 mV were unaltered by Alcian blue treatment, supporting the hypothesis that the transepithelial transport mechanism per se is electroneutral . A calculation of the maximal paracellular mucosa-to-serosa waterflow in response to a lateral intercellular space hypertonicity of 20 mosM demonstrates that in the Alcian bluetreated gallbladder the resulting figure is about three orders of magnitude too low to keep up with the unaltered spontaneous transepithelial net fluid transport. It is therefore concluded that the tight junction pathway in rabbit gallbladders does not serve as a route for net fluid transport.KEY WORDS rabbit gallbladder epitheliumof proximal tubule, gallbladder, and small intestransport pathways . fluid absorption .tine is characterized by a very low transepithelial ultrastructure -Alcian blue electrical resistance compared with the resistances of apical and basolateral cell membranes (2, 12, Isosmotically transporting epithelium such as that 13). The low transepithelial resistance seems to be J. CELL BIOLOGY

Effect of amiloride on sodium and water reabsorption in the rabbit gall‐bladder.

“…6). Since the paracellular route in rabbit gall-bladders does not serve as a pathway for net fluid absorption (Frederiksen et al 1979) the present demonstration of a parallel decrease in net Na+ and water transport upon addition of amiloride must represent a decrease in active, coupled salt and water transport through a cellular pathway.…”

“…Recent studies of epithelial geometry (Rostgaard & Frederiksen, 1981), water permeability (Hill, 1980), and lateral space hypertonicity (Simon, Curci, Gebler & Fr6mter, 1981), however, have led to a critical re-evaluation of this hypothesis. Previous results from rabbit gall-bladder suggest, in fact, that the route for most if not all of the net salt and water transport is through the epithelial cells (Frederiksen et al 1979).…”

Histological Changes in the Human Gallbladder Epithelium associated with Gallstones

“…26 A complete collapse of intercellular spaces was revealed and the tight junction pathway in the gallbladder does not serve as a route for net fluid transport. 27 There is a paucity of information of tight junction proteins in gallbladder epithelium, and disturbances in the structure of these proteins may play a role in the pathogenesis of acute acalculous as well as acute calculous cholecystitis. 28 There is a paucity of information of tight junction proteins in gallbladder epithelium, and disturbances in the structure of these proteins may play a role in the pathogenesis of acute acalculous cholecystitis and acute calculous cholecystitis.…”

Effects of a small serosal hydrostatic pressure on sodium and water transport and morphology in rabbit gall‐bladder

“…In rabbit gall-bladders, however, the route for both salt and water transport seems to be cellular (Frederiksen, M0llgard & Rostgaard, 1979;Frederiksen & Eldrup, 1981). Furthermore, in this epithelium it was observed that energy consumption is closely linked to the transfer rate of fluid volumes rather than to the net transport of solute, an observation which was interpreted as evidence for a mechanical (peristaltic) cellular fluid transport mechanism rather than an ion or salt-pump mechanism (Frederiksen & Leyssac, 1969).…”