The effect of retinoic acid on the proportion of insulin cells in the developing chick pancreas

We assessed the potential role of all-trans-retinoic acid on the developing chick pancreas, specifically with regard to the proportions of insulin cel ls. The endodermal component of the dorsal pancreatic bud of 5-d-old chick embryos was cultured on Matrigel. Retinoic acid (10(-6) or 10(-5) M) was ad ded to a standard serum-free medium. Ham's F12 containing insulin. transfer rin and selenium (F12.ITS). Control grafts Here cultured in F12.1TS alone o r in F12.ITS with DMSO (the diluent for retinoic acid). After 7 d the expla nts Here retrieved, freeze-dried, vapor-fixed, and embedded in resin. Endoc rine cell types were identified by immunocytochemistry. The numbers of insu lin cells were expressed as a proportion of the sum of insulin plus glucago n cells. Retinoic acid had a dose-related effect; the proportion of insulin cells in explants treated with the lower dose of retinoic acid (10(-6) M) was more than twice the proportion of insulin cells in explants treated wit h the higher dose (10(-5) M) of retinoic acid and more than three times tha t of the control grafts.