AJP - Endocrinology and Metabolism, Vol 257, Issue 5 E751-E756, Copyright © 1989 by American Physiological Society
Growth hormone directly stimulates gluconeogenesis in canine renal proximal tubule
S. A. Rogers, I. E. Karl and M. R. Hammerman
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
To characterize the action of growth hormone (GH) on gluconeogenesis in
renal proximal tubule, glucose production was measured in suspensions of
canine renal proximal tubular segments incubated with 1 mM L-alanine, 10 mM
lactate, 1 mM succinate, and various concentrations (10(-11) to 10(-6) M)
of recombinant bovine GH (bGH). Production of glucose increased as a
function of time for 120 min. Bovine growth hormone (10(-6) M) increased
glucose production at 120 min by 55 +/- 16%. Significant enhancement of
glucose production occurred in suspensions of segments incubated with as
little as 10(-10) M bGH. Half-maximal stimulation occurred at between
10(-9) and 10(-8) M. To ascertain whether these actions of bGH are mediated
directly, we determined the effects of insulin-like growth factors (IGFs) I
and II on glucose production. Addition of IGF-I to segments enhanced
glucose production in a concentration-dependent manner. However, incubation
with bGH did not induce measurable IGF-I production in the segments. In
contrast to the action of IGF-I, IGF-II did not affect glucose production.
We conclude that bGH acts directly on cells within proximal tubular
segments to enhance gluconeogenesis. Stimulation of gluconeogenesis in
vitro could reflect a counterregulatory action of GH exerted on renal
proximal tubule in vivo.
