RESUMO
The net absorptive water flux (Jw), the transepithelial potential difference (PD) and the short-circuit current (Isc) were simultaneously measured in the human small intestine in vitro with the following results: 1) An absorptive Jw was observed when the jejunum or the ileum were mounted between two identical standard solutions in the presence of an hydrostatic pressure gradient (delta P) of 13 cm of water (mucosal side positive). 2) The absorptive Jw was a linear function of the applied delta P or the imposed osmotic transepithelial gradient (deltaOsm) in both intestinal segments. The hydrostatic (Phydr) and osmotic (Posm) permeabilities to water for jejunum and ileum were: 0.349 ñ 0.049 cm/s vs. 0.156 ñ 0.022 cm/s and 0.0012 ñ 0.0001 cm/s vs. 0.0019 ñ O.0003, respectively. 3) A fraction of this absorptive Jw was independent of the presence of any hydrostatic, osmotic or chemical gradient and represented the transport associated to movement of water (Jwt). 4) PD and Isc values were similar in the jejunum and in the ileum but the transepithelial resistance (Rt) was significantly greater in ileum than in jejunum. 5) 2 mug/ml of E. coli heat-stable enterotoxin (STa) caused a significant inhibition of the absorptive Jw without modification of Phydr, Posm or Isc. 6) After STa treatment, the absorptive Jwt reverted to a secretory one in the jejunum. In the ileum, STa action caused a 48 per cent decrease in the absorptive Jwt values.
Assuntos
Animais , Humanos , Enterotoxinas/farmacologia , Escherichia coli/enzimologia , Técnicas In Vitro , Intestino Delgado/efeitos dos fármacos , Intestino Delgado/fisiologia , Permeabilidade/efeitos dos fármacos , Transporte Biológico/efeitos dos fármacosRESUMO
El trabajo describe la metodología necesaria para obtener, a partir de la vejiga urinaria de la rana, capas de células aisladas apropiadas para estudios por "patch-clamp". Este resultado se logró combinando presión negativa, digestión enzimática y microdisección. Se obtuvieron registros de canales únicos en las membranas basolaterales, en una situación en la que el epitelio mantenía su polaridad y estructura general