title: Effects of changes in acid base and calcium concentration on fasting serum insulin, proinsulin, and glucose concentrations.
abstract: OBJECTIVE
  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.
authors: Institute of Biochemistry, Glasgow Royal Infirmary.
authors: W S
authors: WS
authors: Smellie
authors: J
authors: J
authors: O'Donnell
authors: H
authors: H
authors: Davidson
authors: J
authors: J
authors: Couper
authors: F C
authors: FC
authors: Logue
mesh_terms: D000136:Acid-Base Equilibrium; D000328:Adult; D000643:Ammonium Chloride / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D005215:Fasting / Q000378:metabolism*; D006801:Humans; D006961:Hyperparathyroidism / Q000378:metabolism; D007328:Insulin / Q000097:blood*; D008297:Male; D011384:Proinsulin / Q000097:blood*; D011547:Pseudohypoparathyroidism / Q000378:metabolism; D017693:Sodium Bicarbonate / Q000494:pharmacology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D000643:Ammonium Chloride; D017693:Sodium Bicarbonate; D011384:Proinsulin; D002118:Calcium