Ontogeny of diazepam binding inhibitor acyl-CoA binding protein mRNA and peripheral benzodiazepine receptor mRNA expression in the rat

The Diazepam Binding Inhibitor/Acyl-CoA Binding Protein (DBI/ACBP) has been implicated in different functions, as acyl-CoA transporter and as an endog enous ligand at the GABA, receptor and the peripheral benzodiazepine recept or (PBR). The latter is thought to be involved in control of steroidogenesi s, We studied the ontogeny of DBI/ACBP and PER mRNA expression in embryos a nd offspring of time-pregnant Long Evans rats by in-situ hybridization with P-33-endlabelled oligonucleotides. Both mRNAs were present in embryo and p lacenta at gestational day (G)11, the earliest stage studied. DBI/ACBP mRNA was strongly expressed from embryonic through mid-foetal stages in central nervous system (maximum in neuroepithelium), cranial and sympathetic gangl ia, anterior pituitary, adrenal cortex, thyroid, thymus, liver and (late fo etal) brown adipose tissue, moderately in testis, heart, lung and kidney. I n brain, a late foetal decrease of DBI/ACBP mRNA was followed by an increas e at postnatal day 6, Peripheral benzodiazepine receptor mRNA expression st arted very low and increased to moderate levels in adrenal cortex and medul la, testis, thyroid, brown adipose tissue, liver, heart, lung, salivary gla nd at mid- to late-foetal stages. Data suggest a significant role of DBI/AC BP at early developmental stages. Both proteins may be involved in the cont rol of foetal steroidogenesis. However, differences in developmental patter ns indicate that additional functions may be equally important during ontog eny, such as the involvement in lipid metabolism in the case of DBI/ACBP.