The portal-arterial (P-A) insulin gradient and arterial plasma c-peptide levels in the control period (−40 to 0 min) and after administration of the glycogen phosphorylase inhibitor (0 to 180 min) in CON and PDN 18-h fasted conscious dogs. The portal-arterial (P-A) insulin gradient and arterial plasma c-peptide levels in the control period (−40 to 0 min) and after administration of the glycogen phosphorylase inhibitor (0 to 180 min) in CON and PDN 18-h fasted conscious dogs. Data are expressed as mean ± SE. Statistical comparisons were made by two-way ANOVA with repeated-measures design, and post hoc analysis was performed with use of the univariate F test when appropriate. *P < 0.05 versus basal period; n = 7 for CON and PDN. Stephanie M. Sherck et al. Diabetes 2001;50:2487-2496 ©2001 by American Diabetes Association