Jak. Martyn et al., REGULATION BY NUTRITION AND AGE OF INSULIN-LIKE GROWTH-FACTOR BINDING-SITES IN-OVINE KIDNEY, The Journal of experimental zoology, 277(5), 1997, pp. 382-389
The insulin-like growth factors (IGFs) are considered to have a role i
n the regulation of renal growth and development. The purpose of the p
resent study was to evaluate the effect of nutritional stress on IGF b
inding in ovine kidney at different postnatal ages. Binding of IGF-I a
nd IGF-II to kidneys of fed and fasted sheep was characterised using h
istological autoradiography, competitive binding assays, and SDS-PAGE.
Nutritional regulation of IGF-I binding was restricted to cells of th
e proximal tubules of two and 14-day-old lambs where we identified an
IGF binding protein which was upregulated in response to fasting and w
here IGF-II binding was also slightly enhanced. Ontogenetic changes oc
curred in the glomeruli where IGF-I binding peaked at 6 months (P less
than or equal to 0.001), and IGF-II binding increased to 4 months and
then plateaued (P less than or equal to 0.01). In the medulla, IGF-II
binding was highest at 4 and 6 months (P less than or equal to 0.05).
From these studies, we conclude that the IGF axis may play a role in
the regulation of the metabolic response to fasting in the kidney of y
oung lambs. Furthermore, the changes with age which are described may
reflect a transition period at 4-6 months, from an initial promotion o
f kidney growth and development in young lambs to establishment of the
metabolic and clearance functions in the adult animal. (C) 1997 Wiley
-Liss, Inc.