Our aim was to determine the effect of growth hormone on non-insulin-mediated
glucose disposal in lactating dairy cows. Following 5 d of subcutaneous
injections of either saline or growth hormone, insulin, somatostatin or
insulin plus
somatostatin were infused for 2 h each, in a series of experiments. Coincident
with
this, unlabelled glucose was infused at a variable rate to maintain a constant
plasma
glucose concentration. Glucose, doubly labelled with deuterium, was also
infused for
the calculations of glucose turnover. Plasma insulin levels were reduced
to nearly
zero by the infusion of somatostatin; under such conditions whole body
glucose
disposal should be non-insulin-mediated. Dairy cows treated with growth
hormone,
which had significantly increased milk yields on the day before the experimental
infusions, did not have different levels of whole body non-insulin-mediated
glucose
disposal when expressed in absolute terms. Growth hormone did not affect
non-mammary
non-insulin-mediated glucose uptake estimated by calculation. Growth
hormone significantly inhibited insulin-mediated glucose uptake when plasma
insulin levels were elevated. Glucose uptake during insulin plus somatostatin
infusion was not significantly different from that of the insulin only
infusion.