Figure 1. Plasma insulin and glucose concentrations in adult and old rats.

Plasma insulin and glucose concentrations were measured in adult and old rats in the four groups: C, fed a 25% AA/protein meal in the presence of insulin secretion; INS−, fed a 25% AA/protein meal in the absence of insulin secretion; AA–, fed a 0% AA/protein meal in the presence of insulin secretion; INS–/AA–, fed a 0% AA/protein meal in the absence of insulin secretion. Results are means ±s.e.m. for 7–8 determinations per group. Plasma insulin is indicated by the columns and the plasma insulin level in diazoxide-treated rats is on average 5.2 ± 0.5 μU ml⁻¹. Plasma glucose concentrations (in g l⁻¹) are indicated in the insets. Three-way analyses of variance were performed to discriminate among effect of age, type of meal, insulin, and their interaction on insulin and glucose concentrations. Values not sharing the same letter differ significantly (P < 0.05). ‡P < 0.05versus adult rats in the corresponding groups.