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Fig. 2 | BMC Biology

Fig. 2

From: GRK2 regulates GLP-1R-mediated early phase insulin secretion in vivo

Fig. 2

Increased early phase insulin secretion and RRP size in GRK2+/− mice. Insulin (a) and glucose (b) were measured after feeding animals for 10 min (early phase insulin secretion) or 4 h (late phase) (same animals were used to assess insulin and glucose levels, WT n = 13, 13, 10 and GRK2+/− n = 11, 11, 7; for 0, 10 min, and 4 h, respectively). oGTT (2 g/kg) was performed in WT and GRK2+/− mice, and insulin (c) and glucose levels (d) were assessed in serum samples 15 min (early phase) and 30 min (late phase) after a glucose gavage (same animals were used to assess insulin and glucose levels, WT n = 7, GRK2+/− n = 10). To explore the status of different pools of insulin granules, mice were injected ip with 1 g/kg arginine (1st ipArg; measured at 2 and 5 min) to elicit insulin secretion from the RRP. A second arginine injection 10 min later (2nd ipArg; measured 2 min later) reveals effects in replenishing the RRP from the RP. In both cases, insulin concentrations in serum are shown in the graph (WT n = 5, 7, 7, 7; GRK2 +/− n = 4, 5, 4, 5 for 0, 2, 5 min and 2 min after 2nd ip Arg, respectively) (e). Mice were injected ip with the sulfonylureas glicazide (10 mg/kg) or glibenclamide (5 mg/kg). Insulin levels were measured at 0 and 15 min and fold increase in serum insulin levels is shown (glicazide: WT n = 4, GRK2+/− n = 4; glibenclamide: WT n = 3, GRK2+/− n = 7) (f). Means ± SEM data are represented, WT: White bars, GRK2+/−: Black bars, statistical analysis was performed by 1-way ANOVA followed by Bonferroni’s post hoc test *p < 0.05; ***p < 0.01

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