AJP - Endocrinology and Metabolism, Vol 251, Issue 5 624-E629, Copyright © 1986 by American Physiological Society
Insulin but not GH directly stimulates growth of transplanted fetal rat paws
P. S. Cooke, L. Higa and C. S. Nicoll
We have investigated whether insulin or growth hormone (GH) can affect
growth of transplanted fetal rat paws by direct and/or indirect actions.
Paws from 15-day rat fetuses were transplanted under the kidney capsule of
adult female hosts, and grown for 7 days. In hypophysectomized (HX) or
diabetic hosts their growth was reduced by 65% and 35%, respectively. The
direct effects of insulin and GH were studied by inserting a catheter
connected to an osmotic minipump into the left renal artery. Thus
transplants on the left (infused) kidney were exposed directly to much
higher concentrations of hormone than were those on the right (uninfused)
side. In HX hosts, infusion of GH (0.1 microgram X g body wt-1 X day-1) had
no effect on growth of paws on either kidney. At 0.3 or 1.0 microgram X g
body wt-1 X day-1 GH caused a dose-related restoration of transplant growth
that was equivalent on both sides. In diabetic hosts infusion of insulin (2
U X kg body wt-1 X day-1) partially restored growth of paws on the infused
kidney without affecting those on the right. Insulin at 6 U X kg body wt-1
X day-1 caused full restoration of growth of the paws on the left and a
partial increase in those on the right. At 9 U X kg body wt-1 X day-1
insulin caused full restoration of transplant growth on both kidneys. These
results indicate that insulin promotes normal growth of transplanted fetal
paws by direct and possibly indirect mechanisms, but the effects of GH are
apparently only indirect.
