Renewal of goblet cell mucus granules during the cell migration along the crypt-villus axis in rabbit jejunum: an immunolabeling study.

A monoclonal antibody against intestinal mucins (5H7) was obtained and used immunolabel thin frozen sections and Epon-embedded sections of rabbit jejunum. It recognized a mucin oligosaccharide, the synthesis of which increased during goblet cell migration along the crypt-villus axis. During the earliest steps in their differentiation, the goblet cells located at the bottom of crypts synthesized mucins devoid of the 5H7 epitope, thus generating unlabeled granules. These unlabeled granules were gradually replaced by more and more labeled granules during the cell maturation. During goblet cell migration along the middle half of the villi, the mucus granules were found to be totally renewed twice. However, some newly formed labeled granules were observed to reach the apical pole of the cells before older unlabeled ones and might have had a faster turnover. At least one glycoconjugate of the goblet cell microvillar membrane also bore the 5H7 epitope. It was rapidly carried from the Golgi apparatus to the apical plasma membrane domain by a transport process that was independent of baseline mucin secretion.