TRANSIENT EXPRESSION OF [D-ALA(2)] DELTORPHIN I-LIKE IMMUNOREACTIVITYIN PRENATAL RAT SMALL-INTESTINE

We studied the distribution of immunoreactive elements for [D-Ala(2)] deltorphin I (DADTI), a delta-opioid receptor ligand, in fetal and pos tnatal rat smalt intestine. DADTI-like immunoreactive cells were detec ted transiently on embryonic Days 20 and 21. Electron microscopic exam ination revealed that positive staining occured in mucous epithelial c ells, either mature goblet cells or undifferentiated cells containing only a few mucous granules. Positive immunoreaction products in mature goblet cells were confined in their apical cytoplasm to the luminal p arts of mucous granule aggregates. The result suggests that a DADTI-li ke molecule(s) is synthesized in rat intestinal goblet cells and is se creted in a diacrine fashion into the intestinal lumen at a late fetal period. The molecule(s) thus secreted may be important for the intest ine of rats just before birth, because DADTI-like immunopositive goble t cells are no longer seen at any postnatal period.