NUCLEAR-DNA CONTENT OF ISOLATED CRYPTS OF BACKGROUND COLONIC MUCOSA FROM PATIENTS WITH FAMILIAL ADENOMATOUS POLYPOSIS AND SPORADIC COLORECTAL-CANCER

The DNA content of the upper one third of the crypt epithelium was com pared with that of the lower two thirds in the background colorectal m ucosa of eight cases of familial adenomatous polyposis (FAP) and eight control cases of sporadic colorectal cancer (SCRC). Intact crypts wer e isolated by incubating fresh lesion free colorectal mucosa in calciu m and magnesium free Hanks' balanced salt solution (CMFH) containing 3 0 mM EDTA for 30 minutes at 37-degrees-C and then agitating in CMFH. T he crypts were then separated from the lamina propria, fixed in 70% et hanol and under a dissecting microscope divided manually into upper an d lower portions. Each portion was digested with pepsin to obtain a su spension of single nuclei, and smears of the nuclei were stained with 4',6,-diamidino-2-phenylindole dihydrochloride (DAPI). Nuclear DNA was determined using a cytophotometric microscope. Results showed that th e DNA content of the epithelium of the upper one third of crypts was d iploid in both FAP and SCRC cases, and that proliferative fractions wi th diploid peaks were present in the lower two thirds of the crypts in both groups. These results support our previous finding that the prol iferative compartment of background crypts is confined to the lower tw o thirds and does not extend to the upper parts of the crypts.