Fluorometric Assays of Glutamic‐Pyruvic Transaminase Activity in Microdissected Pancreatic Islets from Obese‐Hyperglycemic Mice

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Abstract
Hellman, B. Fluorometric assays of glutamicpyruvic transaminase activity in microdissected pancreatic islets from obese‐hyperglycemic mice. Actaphysiol. scand. 1965. 65. 357–363. — The glutamic‐pyruvic transaminase (GF'T) activity was determined in microdissected pancreatic islets from obese‐hyperglycemic mice. The optimal assay conditions for measuring this enzyme in the islet homogenates using a very sensitive procedure based on the fluorescence of pyridine nucleotides in highly alkaline solutions were analysed. An increased islet GPT‐activity was noted in the presence of 2.5 mg % carbutamide, while concentrations above the therapeutic range in the incubation medium inhibited the enzyme in the islets as well as in the exocrine pancreas and liver. When the animals had free access to food the islet GPT‐activity was 0.79 ± 0.07 MKH units as compared with 3.42 ± 0.36 for the exocrine parenchyma and 5.15 ± 0.73 for the liver. A starvation period of 7 days resulted in a 40 % reduction of the islet GPT‐activity: no corresponding decrease being noted in the enzyme activities of the other two tissues. The higher GPT‐activity in the endocrine pancreas in connection with intense insulin secretion supports the view that transamination processes represent an important metabolic feature in the maintenance of the specific endocrine function of the β cells.