Insulin and glucagon secretion after pancreatectomies. Correlation of secretion and hormonal contents of remaining pancreas

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Abstract
We studied whether insulin and glucagon secretory capacities change in relation to the corresponding hormonal contents in the pancreas remnant after pancreas resection. The following groups of dogs were used: sham operated (S-O), left pancreatectomized (L-Px), right pancreatectomized (R-Px), subtotal pancreatectomized (St-Px), and total pancreatectomized (T-Px). Endocrine functions were assessed by intravenous glucose tolerance test (IVGTT) and insulin tolerance test (ITT) in each dog under anesthesia before surgery and 1 wk after. In these five groups, the insulin secretory capacities, assessed as the integrated incremental secretion of immunoreactive insulin (ΣΔIRI) from the IVGTT, decreased to 95 ± 11, 78 ± 9, 48 ± 8, 12 ± 8, and −4 ± 4% of the respective preoperative values, and these values were proportional to the percentage residual weight (100, 64 ± 2, 35 ± 2, 13 ± 2, 0%) and IRI content (100, 59 ± 4, 45 ± 3, 10± 2, 0%) of the pancreas remnant. After surgery, glucagon secretory capacity, the integrated incremental secretion of immunoreactive glucagon (ΣΔIRG) during the ITT, decreased significantly in the L-Px, St-Px, and T-Px groups but not in the R-Px group. The ΣΔIRG values as percentages of the preoperative values were 109 ± 25, 46 ± 11, 89 ± 13, 19 ± 11, and 3 ± 3%, respectively, for the five groups. These values were proportional to the percentage residual IRG contents of the pancreas remnants (100, 48 ± 6, 65 ± 8, 12 ± 2, 0%) rather than to the percentage residual pancreatic weights. Significant correlations were found between the percentage ΣΔIRI and IRI contents ( r = .876, P <.001) and the percentage ΣΔIRG and IRG contents ( r = .775, P <.001) after surgery in individual dogs. The results indicate that the hormonal secretory capacity of these dogs was influenced by the hormone-containing functional mass rather than the weight of the pancreas itself after surgery and that the uneven distribution of glucagon in the pancreas (predominantly concentrated in the tail of the pancreas) should be taken into consideration when discussing hormonal deficiency after pancreatectomy.