Renewal of enterochromaffin cells in the mouse jejunum

Enterochromaffin cells were investigated in the jejunum of adult mice using electron microscope radioautography at various times during continuous infusion of 3H-thymidine. Enterochromaffin cells were classified into three types: biconcave granule cells or type I (60%), large spherical granule cells or type II (13%), and small spherical granule cells or type III (24%). Uncommon spherical granule cells accounted for about 3%. Typical enterochromaffin cells do not divide, but undergo renewal by differentiation of unrecognized precursors in the lower half of intestinal crypts. Labeled enterochromaffin cells appear in crypts by 1-1/2 days, and in villi by 3 days after the infusion started. At 8 days, 80 percent cells were labeled both in crypts and villi. And 8 days after stopping a 4-day infusion most labeled cells had disappeared from crypts and villi. Enterochromaffin cells migrate from crypt to villus, and are presumably extruded from villus tips. The turnover time would he less than eight days