title: Isotonic secretion via frog skin glands in vitro. Water secretion is coupled to the secretion of sodium ions.
abstract: In isolated frog skin at least three different types of cells are engaged in the transepithelial ion and water transport; these are the granular cells, the mitochondria-rich cells and the glandular cells. The experiments presented were carried out on isolated frog skin bathed in Cl- or NO3- Ringer's solution, where the active transepithelial Na+ uptake via the granular cells was blocked by amiloride. Transepithelial current and water flow were measured. When a negative current was passed across the skins (the skins were clamped at -100 mV), the current was mainly carried by a net influx of Cl- via the mitochondria-rich cells. The current had no effect on the transepithelial water movement. This finding indicates that there is nearly no coupling between the Cl- flux and the movement of water via the mitochondria-rich cells. Prostaglandin E2 activates the glandular cells of the exocrine glands in the skin. When prostaglandin E2 was added under these experimental conditions (the skins were clamped at -100 mV, with amiloride in the apical bathing solution, and the glandular secretion of ions was blocked by the use of NO3- Ringer's solution), then the transepithelial current became more negative. This change in current was mainly due to an increase in the Na+ efflux via the glands. Thus PGE2 increase the Na+ conductance of the skin glands. Together with this increase in the Na+ efflux a highly significant increase in the water secretion was observed. The water movement (secretion) across the skin was under these conditions coupled to the PGE2-induced efflux of Na+, and when one Na+ was pulled from the basolateral to the apical solution via this pathway 215 molecules of water followed. This must be due to electro-osmosis (friction between ions and water) or current-induced local osmosis.
authors.affiliation: Institute of Biological Chemistry A, University of Copenhagen, Denmark.
authors.forename: R
authors.initials: R
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D005260:Female; D007477:Ions; D007552:Isotonic Solutions / Q000494:pharmacology; D008297:Male; D009566:Nitrates / Q000494:pharmacology; D011893:Rana esculenta; D000077331:Ringer's Solution; D012867:Skin / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
chemical_list: D002712:Chlorides; D007477:Ions; D007552:Isotonic Solutions; D009566:Nitrates; D000077331:Ringer's Solution; D012964:Sodium; D015232:Dinoprostone