Exogenous activin increases the proportion of insulin cells in the developing chick pancreas in culture.

As activin is believed to be a key signalling factor during early pancreatic development, its influence on the proliferation and/or determination of insulin cells in the developing chick dorsal pancreatic bud was investigated. Dorsal pancreatic buds of 5-day-old chick embryos were explanted on to Matrigel and cultured in serum-free medium (Ham's F12.ITS), to which 1 or 10ng/ml activin was added. After 7 days in culture, the explants were processed for immunocytochemistry and the insulin-positive cells were scored and expressed as a proportion of the sum of insulin and glucagon cells. When compared to the control cultures (Hams F12.ITS alone), activin treatment resulted in respective increases in the proportion of insulin cells of 1.6 and 1.9 fold. It is suggested that activin treatment favours differentiation of the insulin cell pathway relative to glucagon cells.