Endozepine/diazepam binding inhibitor in adrenocortical and Leydig cell lines: absence of hormonal regulation.
One of the many effects which have been attributed to the peptide endozepine/diazepam binding inhibitor (Ep/DBI) is the stimulation of adrenocortical and testicular Leydig cell mitochondrial steroidogenesis. We have used two cell lines (Y-1 mouse adrenal cell tumour and MA-10 mouse Leydig cell tumour), both of which exhibit hormone stimulated steroid production, to investigate the role of Ep/DBI in acute hormone stimulated steroidogenesis. The time course of incorporation of 35S-translabel into Ep/DBI and its turnover rate when the isotope was removed were examined. Cell samples were extracted and separated on Sep-Pak C18 columns and analysed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot analysis followed by fluorography as well as by direct scintillation counting. This allowed us to estimate the in vivo half-life of Ep/DBI and also to investigate the hormonal dependence of the peptide. Data presented here suggest that (i) Ep/DBI levels are not regulated by trophic hormones in these steroidogenic cell lines, and (ii) that the peptide has a relatively long half-life (greater than 3 h), a finding incompatible with suggestions of it having a rapid turnover. Therefore, it seems unlikely that control of Ep/DBI steroidogenic effects is via hormonal modulation of the peptide levels.
Brown
A S
AS
Department of Endocrinology, Prince of Wales Hospital, Randwick, NSW, Australia.
Hall
P F
PF
Shoyab
M
M
Papadopoulos
V
V
D000302:Adrenal Cortex / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D003513:Cycloheximide / Q000494:pharmacology; D026261:Diazepam Binding Inhibitor; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D007700:Kinetics; D007985:Leydig Cells / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000378:metabolism; D051379:Mice; D009479:Neuropeptides / Q000302:isolation & purification / Q000378:metabolism*; D013256:Steroids / Q000096:biosynthesis*; D013462:Sulfur Radioisotopes; D014407:Tumor Cells, Cultured
D026261:Diazepam Binding Inhibitor; D009479:Neuropeptides; D013256:Steroids; D013462:Sulfur Radioisotopes; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone; D003513:Cycloheximide; D008715:Methionine