Vid vilken glukosnivå frisätter kor insulin?
Six cows were subjected to an intravenous glucose tolerance test (GTT) to evaluate the amount of glucose that is needed to stimulate the release of insulin from pancreas. Four of the cows were in early lactation and two were non-lactating and not pregnant. Series of blood-samples were collected to analyze the concentration of insulin and glucose in the blood. The cows were given lower levels of glucose than have been used in earlier glucose tolerance tests. The levels of glucose given were 7,5 mg/kg BW, 15 mg/kg BW, 30 mg/kg BW and 50 mg/kg BW. It was shown that only a small increase in blood glucose was needed to stimulate the release of insulin from pancreas. A rise of 0,25 mmol/l of blood glucose triggered release of insulin. The non-lactating cows had higher levels of glucose and insulin than the lactating cows, both before and after treatment. Two different tests were used to analyze insulin; Coat-A-Count Insulin radioimmunoassay (DPC Los Angeles, USA) and Mercodia, Bovine Insulin ELISA (Mercodia AB, Uppsala). The results from Mercodia were higher and detected lower levels of insulin compared to Coat-A-Count.