title: Glucose levels at the site of subcutaneous insulin administration and their relationship to plasma levels.
abstract: OBJECTIVE
  To examine insulin's effect on the tissue glucose concentration at the site of subcutaneous insulin administration.
  
  
  METHODS
  A CMA-60 microdialysis (MD) catheter and a 24-gauge microperfusion (MP) catheter were inserted into the subcutaneous adipose tissue of fasting, healthy subjects (n = 5). Both catheters were perfused with regular human insulin (100 units/ml) over a 6-h period and used for glucose sampling and simultaneous administration of insulin at sequential rates of 0.33, 0.66, and 1.00 units/h (each rate was used for 2 h). Before and after the insulin delivery period, both catheters were perfused with an insulin-free solution (5% mannitol) for 2 h and used for glucose sampling only. Blood plasma glucose was clamped at euglycemic levels during insulin delivery.
  
  
  RESULTS
  Start of insulin delivery with MD and MP catheters resulted in a decline of the tissue glucose concentration and the tissue-to-plasma glucose ratio (TPR) for approximately 60 min (P < 0.05). However, during the rest of the 6-h period of variable insulin delivery, tissue glucose concentration paralleled the plasma glucose concentration, and the TPR for MD and MP catheters remained unchanged at 83.2 +/- 3.1 and 77.1 +/- 4.8%, respectively. After subsequent switch to insulin-free perfusate, tissue glucose concentration and TPR increased slowly and reattained preinsulin delivery levels by the end of the experiments.
  
  
  CONCLUSIONS
  The results show the attainment of a stable TPR value at the site of insulin administration, thus indicating that insulin delivery and glucose sensing may be performed simultaneously at the same adipose tissue site.
authors.affiliation: Department of Internal Medicine, Division of Endocrinology and Nuclear Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Lindpointner
authors.forename: Stefan
authors.initials: S
authors.lastname: Korsatko
authors.forename: Gerd
authors.initials: G
authors.lastname: Köhler
authors.forename: Hans
authors.initials: H
authors.lastname: Köhler
authors.forename: Roland
authors.initials: R
authors.lastname: Schaller
authors.forename: Lukas
authors.initials: L
authors.lastname: Schaupp
authors.forename: Martin
authors.initials: M
authors.lastname: Ellmerer
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Pieber
authors.forename: Werner
authors.initials: W
authors.lastname: Regittnig
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000187:drug effects*; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D055104:Infusions, Subcutaneous; D007328:Insulin / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D008962:Models, Theoretical; D040521:Subcutaneous Tissue / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D005947:Glucose