Effects of nutrients on pancreatic hormone secretion from the chicken pancreas in vitro

A collagenase-free technique is described for isolation and perifusion of chicken pancreatic "microfragments". The micro- fragments represent at least a two-fold purification of islet tissue yet possesses no detectable proteolytic activity. Basal secretion of three pancreatic hormones from the pancreatic microfragments rapidly stabilizes and the tissue remains viable for at least 90 minutes. Perifusion of these microfragments was carried out to gather further knowledge as to the (direct) sensitivity of the avian pancreas to the secretogogic potential of various nutrients. When the microfragments were pre-incubated in a control medium containing 200 mg glucose/dl, insulin output from the perifused microfragments could be increased only if medium glucose was increased to 700 mg/dl. This relative insensitivity of insulin secretion to changes in medium glucose is in agreement with results obtained from other isolated avian pancreas preparations. Contrary to the suppressive effects of hyperglycemia in vivo, increasing the glucose concentration of the perifusion medium produced only a slight increase in APP output from the microfragments. Glucagon release was reduced when medium glucose was increased. A significant reduction in glucagon secretion occurred when the medium glucose was increased from 200 mg/dl to 500 mg/dl or to 700 mg/dl. This may indicate that in the chicken the glucose recognition system of the A-cells is more sensitive than is the glucose recognition system of the B-cells.