The effect of gastric juice on electrolyte transport by the colon - abstract

Replacement of the oesophagus by the colon is a widely accepted method of treatment for neoplasms or benign strictures of the oesophagus. The colon normally plays an important role in the re-absorption of water and electrolytes in the body. In addition, peptic ulceration sometimes occurs in the colonic transplant. It is therefore important to study the effect of gastric juice on the colon. Trained dogs with chronic Pavlov pouches and isolated segments of colon were the experimental model. Gastric juice was collected from the Pavlov pouches. 25ml of gastric juice was instilled into the colon and samples aspirated at intervals over the next 6 hours. The samples were then analysed for sodium, patassium, chloride, bicarbonate, pH and osmolality. This response was compared with that obtained following the instillation of isotonic solutions of HCI, NaCi, mannitol and (NH4)2SO4. The results obtained show that gastric juice was rapidly and effectively buffered by the colon and there was no increase in the production of mucous. Hydrogen ions were absorbed in exchange for sodium and there was no effect on potassium or chloride transport. There was a decrease in the bicarbonate content of colonic samples. There was no evidence of active water transport (AU)

Active transport of the chloride ion by the colon - abstract

The present data represent some results of our continuing studies on the mechanisms of electrolyte transport in the colon. Trained dogs with chronic isolated segments of colon were used, and the transport of chloride ion was studied by instilling the following electrolyte solutions into the colon: sodium chloride (154 mEq/L, 100 mEq/L), Mannitol (5 percent) choline choride (100 mEq/L), lithium chloride (100 mEq/L), lithium chloride (60 mEq/L) plus potassium chloride (40 mEq/L), lithium chloride (75 mEq/L) plus sodium bicarbonate (75 m Eq/L). All solutions were made isotonic whenever necessary by the addition of mannitol and all contained the non-absorbable maker polyethylene glycol (PEG). Samples of colonic fluid were taken at intervals over a six-hour period following the instillation of solution into the isolated colonic segment. The samples were analysed for Na, K, Cl, HCO3 - pH, osmolality and PEG. The electrical potential difference across the colon was measured in several experiments. Chloride ion transport was also studied following the administration of Diamax or Aldosterone, mucosa. There was no evidence of active water transport. The mucosa is normally electrically negative with respect to serosa; however, in the presence of choline chloride the mucosa becomes electrically positive with respect to serosa. Our data also show that the chloride ion is actively transported against both an electrical and a chemical gradient. In addition chloride can be transported in the absence of sodium, but in the presence of sodium can be transported more rapidly than that ion. Chloride transport is to some extent linked to sodium transport and also to bicarbonate transport (AU)

Electrolyte metabolism in the colon - abstract

Studies were designed to determine the role of the colon in electrolyte homeostasis, and to analyse some of the factors which affect electrolyte transport in the colon. These studies were carrried out in humans by the analysis of faecal fluid electrolytes, and in rats and dogs by in-vivo isolated loops of colon. The results obtained show that, particularly under conditions of electrolyte depletion, the colon plays an important role in electrolyte homeostasis. There is a suggestion that although there is a relationship between the transport of sodium and potassium, transport of potassium may occur independently of sodium transport. There may be a relationship between the transport of potassium and bicarbonate and there is a relationship between the transport of chloride and bicarbonate (AU)

Ion transport in rat-liver slices

Rat-liver slices lose potassium when leached in cold saline solution, and reaccumulate potassium when incubated in warm oxygenated Ringer solution. The maximum rate of accumulation is about 5 m-equiv. of potassium/kg. dry wt./min. After the initial 10 minutes of incubation sodium loss and potassium uptake are in a 1:1 ratio. In the first 10 minutes of incubation nu potassium accumulates, but much sodium and water are lost. Conditions necessary for a sustained uptake of potassium to take place are described; O-tocopherol must be given to rats 24 hours before they are killed(AU)