Effects of changes in acid base and calcium concentration on fasting serum insulin, proinsulin, and glucose concentrations. Issue 11 (November 1994)

• Record Type: Journal Article
• Authors: Smellie, W S; O'Donnell, J; Davidson, H; Couper, J; Logue, F C
• Is Part Of: Journal of clinical pathology. Volume 47:Issue 11(1994)
• Page Start: 982
• Page End: 985
• Publication Date: 1994-11
• Subjects: Pathology -- Periodicals; Pathology, Molecular -- Periodicals; 616.0705
• DOI: 10.1136/jcp.47.11.982
• Languages: English
• ISSNs: 0021-9746

Abstract

Abstract : AIMS--To test the hypothesis that alterations in acid base or calcium concentration may affect proinsulin processing or the insulin secretion mechanism. METHODS--Changes in proinsulin secretion or cleavage were assessed by measuring serum intact proinsulin and immunoreactive insulin concentrations in three models of acid base and calcium disturbance: (1) subacute changes in acid base status in six volunteers who received oral placebo, ammonium chloride, or sodium bicarbonate for three five day periods; (2) acute changes in calcium concentration in eight subjects who received 25 mmol oral calcium; (3) chronic changes in calcium concentration in seven patients with primary hyperparathyroidism and five with pseudohypoparathyroidism. RESULTS--Acid base changes were confirmed by rises in serum bicarbonate concentrations (p < 0.01). No changes in serum insulin, intact proinsulin, or the proinsulin:insulin molar ratio were found. Serum calcium concentrations increased (2.49 v 2.38 mmol/l; p < 0.05) and parathyroid hormone concentrations decreased (1.1 v 1.9 pmol/l; p < 0.01) two hours after acute calcium loading. There were no significant differences in serum glucose, insulin, or intact proinsulin concentrations. Fasting proinsulin concentrations were significantly lower in the hyperparathyroid group (1.1 v 2.1 pmol/l; p < 0.05) and increased significantly after parathyroidectomy (2.1 v 1.1 pmol/l; p < 0.05). CONCLUSIONS--The results indicate that subacute acid base changes do not affect proinsulin cleavage. Although acute calcium loading has no demonstrable effect, chronic hypercalcaemia may influence the mechanism of insulin secretion.