QUANTIFICATION OF THE COLONIC MUCOUS CELL-POPULATION DURING PROTRACTED STRESS IN RATS

The mucins contained in goblet cells of the descending colon of rats were histochemically labelled by Alcian blue pH 2.5 and quantified in an image analyzer (Cortex Controller) in 55 Sprague-Dawley rats. After transportation to the stress laboratory, 25 rats were compelled to swim for two consecutive hours/day either only once (five rats), for one week (five rats), two weeks (five rats), four weeks (five rats) or eight weeks (five rats). Twenty-five additional rats were only transported to the stress laboratory (i.e. 'sham-handled') controls, either once (five rats), one week (five rats), two weeks (five rats), four weeks (five rats) or eight weeks (five rats). The remaining five rats were 'untransported' resting rats (i.e. day 0). The results were expressed in per cent of Alcian blue stain cells/total mucosa analyse. When various time intervals were compared with those of day 0 (i.e. horizontal study) it was found that two hours and one, two weeks swimming resulted in a significantly decreased percentage of mucin-containing cells (p < 0.001). Contrariwise, a significantly increased mucous-cell population was found after eight weeks swimming. 'Shamhandled' rats had at two and eight weeks a significantly increased (p < 0.001) percentage of mucous-producing cells. Swimming and 'sham-handled' controls were compared at each time interval (i.e. vertical study). The results indicated that swimming rats had a significantly lower (p < 0.001) percentage of mucin-containing cells than transported rats had at day 1 and at one, two and eight weeks. It is concluded that during the first two weeks of daily physical stress, the mucin-cell population of the descending colon of the rat is reduced. This is followed by a hyperproduction of mucin-containing cells. A similar hyperproduction was found at 8 weeks in control rats, suggesting that the mucin-cell population may be altered even in the absence of physical stress. The possibility that protracted transportation acted as a physical stress in our control rats should be considered.