Diabetes, Vol 38, Issue 6 686-690, Copyright © 1989 by American Diabetes Association
Characterization of insulinlike growth factor I produced by fetal rat pancreatic islets
R Scharfmann, M Corvol and P Czernichow
Institut National de la Sante et de la Recherche Medicale (Unit 30), Hopital des Enfants Malades, Paris, France.
Pancreatic islets were prepared from 22-day-old rat fetuses. After 5 days
of culture in dishes allowing cell attachment, neoformed islets were kept
free floating in RPMI-1640 medium (16.5 mM glucose, 1% fetal calf serum).
The islets were then pulsed with [3H]leucine and [35S]methionine for 24 h.
The conditioned medium was acidified with acetic acid (final pH 2.7),
desalted, concentrated, and gel filtered on Bio-Gel P100 in acid
conditions. The radioactive material that comigrated with immunoreactive
insulinlike growth factor I (IGF-I) produced by the islets was pooled,
concentrated, and further characterized by reverse-phase high-performance
liquid chromatography on a C18 Bondapak column with a linear gradient of
acetonitrile (20-80%). The radioactive material that eluted as pure IGF-I
(40% acetonitrile) was further studied by chromatofocusing on a Pharmacia
PBE 94 column. A sharp radioactive peak containing [3H]leucine and
[35S]methionine was eluted at pH 8.55. This material was immunoprecipitated
with an antiserum to IGF-I. This study demonstrated that fetal islet cells
synthesize molecules that are, by several criteria, equivalent to native
IGF-I.