Insulin-like growth factor-II/mannose-6-phosphate receptors are increased in hepatocytes from regenerating rat liver.
Insulin-like growth factor-II (IGF-II) receptor levels were determined in hepatocytes from sham-operated and two thirds hepatectomized rats. [125I]IGF-II binding to confluent cultures increased 2-fold in cells isolated 24 and 48 h after hepatectomy compared to that in cells from sham-operated rats. Receptor levels increased from 1.74 +/- 0.14 x 10(4)/cell (sham-operated) to 3.60 +/- 0.31 x 10(4)/cell (hepatectomized; P = 0.002), with no change in affinity of IGF-II binding (Ka = 6.4 x 10(9) M-1). As previously reported, receptor levels increased in cells plated at low density, but this effect was decreased in cells from hepatectomized rats (80% increase) compared to that in cells from control rats (300% increase). Serum IGF-I levels decreased 50% 24 h after partial hepatectomy (P less than 0.001), but returned to normal levels by 48 h. However, IGF-I synthesis was not decreased in hepatocytes isolated 24 h after partial hepatectomy, suggesting that decreased serum levels are due to decreased liver mass. Circulating IGF-II levels were not altered by partial hepatectomy, and IGF-II production was not detected in hepatocytes from sham-operated or hepatectomized rats. Transforming growth factor-beta is thought to terminate hepatocyte proliferation upon complete liver regeneration. In hepatocytes from sham-operated or hepatectomized rats transforming growth factor-beta totally blocked DNA synthesis, but had no effect on elevated IGF-II receptor levels after partial hepatectomy. Concomitant with increased IGF-II receptor levels, hepatocytes from hepatectomized rats were more sensitive to IGF-II stimulation of DNA synthesis. [3H]Thymidine incorporation in the presence of epidermal growth factor (50 ng/ml) was stimulated 66% by IGF-II (300 ng/ml) in control cells compared with 220% in cells from hepatectomized animals. These results suggest that IGF-II and the IGF-II receptor may play a role in liver regeneration.
Scott
C D
CD
Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia.
Baxter
R C
RC
D000818:Animals; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D006498:Hepatectomy; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism* / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008115:Liver Regeneration / Q000502:physiology*; D051381:Rats; D011920:Rats, Inbred WF; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*; D015291:Transforming Growth Factors / Q000494:pharmacology
D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D015291:Transforming Growth Factors; D004247:DNA