PROLIFERATION KINETICS IN EPITHELIUM OF GUINEA-PIG COLON

Autoradiographs of crypts of guinea-pig colon labelled with ³H-thymidine were quantitatively analysed. The analysis involved: (a) comparison of proliferation parameters in crypts situated in two well-defined regions of colonic folds, i.e. in the top and the basal parts of the fold, and (b) comparison of proliferation parameters in the lower and in the upper parts of an individual crypt. The results provide evidence that: (1) Crypts situated in the top region of folds are significantly longer than those situated in the basal region. (2) The duration of cell cycle and its phases is similar in the crypts of the two regions examined. (3) The rate of ³H-thymidine uptake is higher in the middle than in the initial and final parts of the S phase, and its pattern is the same for the crypts of the two regions of the fold as well as for the parts of the individual crypt. (4) The proliferating pool size is larger in crypts situated in the top than in the basal region of the fold. (5) The proliferating pool size is larger in the lower parts of crypts from each region than in the upper parts. Control of cellular proliferation in the crypt epithelium is considered to operate separately at the level of the individual crypt and at the level of a group of crypts situated in a given region of the colonic wall.