Non-insulin- and insulin-mediated glucose uptake in dairy cows.
Four mid-lactation Holstein dairy cows (mean milk yield on day of experiments 26.1 kg/d) were used in a series of experiments to establish the contribution of non-insulin-mediated glucose uptake to total glucose uptake at basal insulin concentrations. A secondary objective was to determine whether somatostatin affects the action of infused insulin. In part I of the experiment a primed continuous infusion [6,6-2H]glucose (45.2 micrograms/kg per min) was begun at time 0 and continued for 5 h. After 3 h of [6,6-2H]glucose infusion (basal period) a primed continuous infusion of insulin (0.001 i.u./kg per min) was administered for 2 h. Coincidental with the insulin infusion, normal glucose was also infused in order to maintain the plasma glucose concentration at euglycaemia. Part II of the experiment was the same as part I except that somatostatin was infused for 2 h (0.333 micrograms/kg per min) instead of insulin. In part III of the experiment both insulin and somatostatin were infused for the final 2 h. Plasma insulin levels were increased by insulin infusion (to 0.1476 to 0.1290 i.u./l for parts I and III respectively) and were reduced by somatostatin infusion in part II (to 0.006 i.u./l) relative to the basal periods (mean 0.021 i.u./l). Glucose uptake during somatostatin infusion (2.50 mg/kg per min; part II) was 92.0% of that observed in the respective basal period (2.72 mg/kg per min). Circulating insulin levels were much lower than the dose of insulin that causes a half maximal effect on glucose uptake (0.06-0.10 i.u./l for ruminants); consequently insulin-mediated glucose uptake was probably absent in part II. Secondly, glucose uptake following insulin only infusion (4.05 mg/kg per min) was significantly lower than that observed when insulin plus somatostatin was infused (4.69 mg/kg per min), indicating that somatostatin either directly or indirectly enhanced the action of insulin on glucose uptake.
Rose
M T
MT
Department of Animal Physiology, National Institute of Animal Industry, Ibaraki, Japan.
Obara
Y
Y
Itoh
F
F
Hashimoto
H
H
Takahashi
Y
Y
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002417:Cattle / Q000378:metabolism*; D003903:Deuterium; D005260:Female; D005934:Glucagon / Q000097:blood; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism*; D013006:Growth Hormone / Q000097:blood; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D007700:Kinetics; D008657:Metabolic Clearance Rate; D013004:Somatostatin / Q000494:pharmacology
D001786:Blood Glucose; D007328:Insulin; D013004:Somatostatin; D013006:Growth Hormone; D005934:Glucagon; D003903:Deuterium; D005947:Glucose; D006854:Hydrocortisone