Isolation of a murine glucose-dependent insulinotropic polypeptide (GIP) cDNA from a tumor cell line (STC_(6-14)) and quantification of glucose-induced increases in GIP mRNA

摘要

A 537 base, pair cDNA clone for murine GIP has been isolated. The elucidated sequence encodes an open reading frame of 432 base pairs which codes for a 1.44 amino acid precursor. Murine GIP is predicted to differ from the human hormone by three amino acid substitutions: argininc for histidinc at position 18, arginine for lysine nt position 30 and serine for lysine at position 34. GIP mRNA levels in STC6-I4 cells incubated in the presence of varying glucose concentrations was investigated using a competitive-PCR method. In the presence of a 5-mM glucose stimulus, 1 X 10~5 GIP cells were found to contain 3.9 ± 0.59 amol of GIP mRNA while the same number of cells contained 11.6 ± 1.4 amol when subjected to a high (25 mM) glucose stimulus.