title: Human duodenal spheroids for noninvasive intracellular pH measurement and quantification of regulation mechanisms under physiological conditions.
abstract: Three-dimensional cell cultures (spheroids) of biopsies of human duodenum were used to develop a new noninvasive method for studying intercellular and intracellular mechanisms. Through examinations of intracellular pH regulation, high functional similarity to native tissue could be shown, as already evidenced morphologically. A special microperfusion chamber was developed to fix individual spheroids physically to a nylon net, via laminar perfusion flow through the chamber. A significant improvement over current fixation methods was shown by the increase of cell viability almost up to 100%. Viability of the spheroids was confirmed by trypan blue exclusion, by a LIVE/DEAD viability/cytotoxicity kit, and by BCECF distribution. Intracellular pH was measured by use of the pH-sensitive fluorescence dye BCECF. To investigate the intracellular pH regulation, spheroid-like vesicles were acidified by NH4Cl prepulse technique. The subsequent active intracellular pH recovery was blocked with Na+-free Krebs Henseleit (KH) solution, with amiloride KH (inhibitor of the Na+-H+-exchanger), or with H2DIDS KH (inhibitor of the HCO3(-)-Cl(-)-exchanger and Na+-HCO3(-)-cotransporter). The intracellular pH of the spheroids was 7.31 +/- 0.05. pH-backregulation after acidification was prevented by sodium-free buffer, amiloride, and H2DIDS. These experiments indicated the presence of a Na+-H+-exchanger and a Na+-HCO3(-)-cotransporter. In conclusion, the human duodenal spheroid is an excellent physiological system for in vitro studies of the human duodenum.
authors.affiliation: Department of General Surgery, University of Tuebingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Weinlich
authors.forename: Christina
authors.initials: C
authors.lastname: Baumstark
authors.forename: Engin
authors.initials: E
authors.lastname: Usta
authors.forename: Horst D
authors.initials: HD
authors.lastname: Becker
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sessler
mesh_terms: D004386:Duodenum / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D005452:Fluoresceins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008854:Microscopy, Electron
chemical_list: D005452:Fluoresceins; C057433:2',7'-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester