Effects of insulin-like growth factors I and II on growth and differentiation of transplanted rat embryos and fetal tissues.
The objective of our study was to obtain comparative information on the roles of insulin-like growth factors (IGFs) I and II in the growth and differentiation of rat embryos and fetuses in an in vivo experimental system. Ten-day-old rat embryos or 16-day-old fetal rat paws were transplanted under the capsule of both kidneys of syngeneic hosts, where they grew rapidly, and tissue differentiation occurred in an essentially normal manner. Infusion of a rabbit antiserum to human (h) IGF-I for 6 days into the renal artery of one kidney caused only a slight inhibition (approximately 20%) of growth of transplanted embryos on that kidney. However, 9 days of treatment with the antiserum caused highly significant growth retardation of transplanted embryos by 40-45%. Exposure of fetal paws to the same antiserum for 9 days inhibited their growth by 27%. Infusion of synthetic hIGF-II or partially purified rat IGF-II [(MSA)multiplication-stimulating activity], for 6 days stimulated the growth of embryo transplants directly, and MSA was more effective than hIGF-II. By contrast, infusion of purified natural hIGF-I did not promote their growth. Growth of fetal paw transplants in hypophysectomized (HX) hosts was reduced by 70% compared to that in intact hosts. In the HX hosts infusion of the MSA was more effective than the hIGF-I at promoting the growth of paw transplants. Both MSA and IGF-I promoted ossification in the fetal paws in the HX hosts. These results suggest that both IGFs could be involved in regulating the growth and differentiation in prenatal rats, and IGF-II may be the more effective of the two factors as a growth-promoting agent in utero.
Liu
L
L
Department of Physiology-Anatomy, Cancer Research Laboratory, University of California, Berkeley 94720.
Greenberg
S
S
Russell
S M
SM
Nicoll
C S
CS
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D004622:Embryo, Mammalian / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000502:physiology*; D007016:Hypophysectomy; D007106:Immune Sera; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D009924:Organ Culture Techniques; D051381:Rats; D013002:Somatomedins / Q000494:pharmacology*; D013370:Subrenal Capsule Assay
D007106:Immune Sera; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II