The use of fluorocarbon emulsion in the Ussing chamber.

Abstract

The study of the biochemical processes related to H secretion has been seriously impeded by the low rates of secretion obtained in vitro. Davenport has shown that higher rates can be obtained if hyperbaric conditions are instituted (1). This suggests that inadequate oxygenation imposes usually a serious limitation on the secretory activity of parietal cells whose metabolism is largely mitochondrial and oxidative. This study shows that the problem of inadequate oxygenation can be partly overcome by the use of fluorocarbon, a liquid with high gas capacity (60 vol % O2) (2). Frog gastric mucosa stripped of external muscle layers, was mounted in an Ussing chamber, and acid rate, potential difference, resistance, and short circuit were measured by standard procedures (3). The circulation on the mucosal side was maintained by an airlift system utilizing 95% O2 and 5% CO2. The serosal side was circulated by a peristaltic pump, the outflow of which passed through a Teflon gassing coil immediately prior to entry into the chamber. Gassing on this side was also with 95% O2 and 5% CO2. The solutions used were: mucosal solution 100 mM Na, 5 mM K, 105 mM Cl with the pH stat set at 3.8; serosal solution standard frog Ringer emulsified with 20% (v/v) FC80 fluorocarbon (perfluoro tributylamine) using pluronic F68 (Wyandotte Chemical Corporation) 8% as emulsifier. Emulsification was carried out by sonicating in ice for 1 hr with a Brownill sonic probe at maximum intensity. Inhibitors or stimulants of secretion were added directly to the serosal solution. Secretory rates obtained from Rana pipiens gastric mucosa range from 1 to 5 μE cm-2 hr-1, though occasionally higher rates are observed in the initial period of an experiment. In this, as in other laboratories, the mean secretory rate in the presence of histamine has been about 3.5 μE cm-2 hr-1.