Figure 5.

Regulation of hormone secretion is defective in Foxa2^loxP/loxP; Ins.Cre mice. All perifusion studies were performed at least three times and representative trace is shown for each experiment. (a) Pancreata from two postnatal day 8 (P8) controls (open squares) and Foxa2^loxP/loxP; Ins.Cre (Mutant, filled diamonds) mice were perifused as described in Materials and Methods with increasing concentrations of glucose from 0 to 15 mM glucose at a rate of 1 mM per minute. Fractions were taken every minute, and the insulin concentration was determined by RIA. (b) Continuation of experiment in a with a glucose ramp decreasing from 26 to 0 mM glucose, changing the glucose concentration at a rate of 1 mM per minute (represented by triangle). At the end of the experiment, 15 mM potassium chloride (KCl) was added to the perifusate, represented by the bar. Fractions were taken every minute, and insulin concentrations were determined by RIA. (c,d) Pancreata from two P8 control (open squares) and Foxa2^loxP/loxP; Ins.Cre (filled diamonds) mice were perifused as described in Experimental Procedures with addition of secretagogue, 15 mM amino acid mixture (AAM) plus 2 mM glutamine or 15 mM KCl (KCl) as indicated. Fractions were taken every minute, and insulin (c) and glucagon (d) concentrations were determined by RIA. c and d represent hormone concentrations of fractions from the same perifusion experiment.