EXPRESSION OF IMMUNOREACTIVE ACTIVIN-A IN FETAL-RAT PANCREAS

Expression of activin A in fetal rat pancreas was studied immunohistoc hemically by using anti-activin A antibody. On embryonic day 12 (E12), cells in cap-like pancreatic anlage were stained with anti-activin A antibody. In these sections, no immunoreactive insulin or glucagon was observed. On E13.5, cells containing immunoreactive activin A were ob served in pancreatic anlage. These cells were also stained by both ant i-glucagon and anti-insulin antibodies. On E15, a cluster of cells cou ld be recognized as a primitive islet. In the primitive islet, cells c ontaining immunoreactive activin A were observed. Activin-positive cel ls were located mainly in the mantle of the primitive islet but some w ere located in the core of the primitive islet. These activin-positive cells also expressed glucagon. Among them, cells also containing insu lin were observed. In addition to activin-positive cells, cells contai nig only insulin were detected in the core of the primitive islet. The se results indicate that immunoreactive activin A is expressed in feta l pancreas. The expression of activin A is an early event during the d evelopment of pancreatic endocrine cells.