A quantitative immunofluorescent study of the endocrine cell populations in the developing human pancreas

The immunofluorescent cell content of the pancreas of 8--40-wk fetuses and of 1.5--5-mo Caucasian infants was quantitatively evaluated using anti-insulin, anti-glicentin, anti-glucagon, anti-somatostatin, and anti-pancreatic polypeptide antisera. The most significant findings are: (1) the pancreas of 8--10 wk fetuses contains a sizable population of endocrine cells reacting exclusively to anti-glicentin antiserum. This cell population decreases and disappears in later stages and is replaced by the adult type glucagon/glicentin immunoreactive cell; (2) the pancreatic polypeptide-rich region shows a lower relative endocrine cell content as compared with the glucagon-rich region and its islets appear smaller; (3) in the total pancreas, the relative (volume density) and absolute (microliter) insulin cell content increases regularly with age, while the relative volume of glucagon cells peaks in fetal life (wk 17--20) to decrease in infants, although remaining at higher levels than in adults; the relative and absolute volumes of somatostatin cells are elevated in fetal and infant stages studied where they represent the second most abundant cell type, while pancreatic polypeptide cells appear to least abundant cells during prenatal and infant life. These data show several differences with the pattern of the respective endocrine cell populations in the adult pancreas.