Diabetes, Vol 36, Issue 4 465-471, Copyright © 1987 by American Diabetes Association
Somatomedin-C in human fetal pancreas. Cellular localization and release during organ culture
DJ Hill, A Frazer, I Swenne, PK Wirdnam and RD Milner
The presence of somatomedin-C/insulin-like growth factor I (SM-C/IGF-I) was
investigated in human fetal pancreatic glands obtained after
prostaglandin-induced abortion at 14-17 wk of gestation. Pancreatic
explants were cultured in medium containing 11.1 or 22.2 mM glucose and 20%
fetal calf serum for 8-10 days. During this period they were exposed, on
two separate occasions, to serum-free culture medium for 24 h. SM-C/IGF-I
and insulin were measured radioimmunologically in the serum-free media and
in acid-ethanol-extracted homogenates of the cultured explants. SM-C/IGF-I
was measurable in the conditioned media only after extraction by
reverse-phase chromatography to remove somatomedin-binding proteins. On gel
filtration at neutral pH of extracted medium samples, the immunoreactive
SM-C/IGF-I was recovered in the region of the homogeneous peptide with an
apparent molecular weight of 7000-8000. Explants cultured in 22.2 mM
glucose contained more SM-C/IGF-I and had a tendency to release more of the
peptide into the culture medium than explants cultured in 11.1 mM. There
was no difference in insulin content or release between the two groups. By
immunocytochemistry, SM-C/IGF-I was localized to the beta-cells of the
endocrine pancreas in both freshly fixed tissue and cultured explants. We
conclude that the human fetal pancreas contains SM-C/IGF-I and secretes the
peptide during tissue culture. The presence of SM-C/IGF-I in the islets of
Langerhans may contribute to the growth and development of the
insulin-producing beta-cell.