Dexamethasone, but not stress, induce measurable changes of mitochondrial benzodiazepine receptor mRNA levels in rats.
The expression of the mitochondrial benzodiazepine receptor gene was assayed by a semi-quantitative non-radioactive reverse transcriptase polymerase chain reaction (RT-PCR) assay. The level of amplified mitochondrial benzodiazepine receptor mRNA was expressed as a ratio of either glyceraldehyde-3-phosphate dehydrogenase (GAPDH) or beta-actin mRNA co-amplified in the same RT-PCR assay. The relative amounts of mitochondrial benzodiazepine receptor RNA in several rat tissues were found to be similar to the previously reported relative amount of mitochondrial benzodiazepine receptor binding sites. The level of these binding sites has also been reported to be altered by stress stimuli. In this study we specifically measured the effect of stress on the mRNA levels of the mitochondrial benzodiazepine receptor as an alternative method to the binding assay in an attempt to understand the mechanism by which stress alters binding. Sprague-Dawley male rats were either forced to swim for 15 min in 18 degrees C water or restrained in a plastic cylinder for 45 min either once, or twice daily for 7 days. Neither the swim stress, nor acute or chronic restraint stress, caused a measurable statistically significant relative change in mitochondrial benzodiazepine receptor mRNA in the adrenal gland, kidney, testis and olfactory bulb. However, daily treatment of rats for 7 days with 4 mg/kg of dexamethasone caused a significant decrease in mitochondrial benzodiazepine receptor gene expression in adrenal glands. This finding and the measurement of the relative levels of mitochondrial benzodiazepine receptor mRNA in the various tissues indicate that mitochondrial benzodiazepine receptor density is regulated to some extent at the gene expression level. However, the lack of detectable stress-induced changes in mRNA levels for this receptor seem to indicate that either mRNA changes were below detectable levels or that other mechanisms may be involved in the previously reported stress-induced changes of mitochondrial benzodiazepine receptor density. Because the focus of this work was on the regulation of mitochondrial benzodiazepine receptor gene expression, ligand binding studies to determine changes in receptor densities were not performed.
Siripurkpong
P
P
Neuro-Behavioural Biology Center, Institute of Science and Technology for Research and Development, Mahidol University, Nakorn Pathom, Thailand.
Harnyuttanakorn
P
P
Chindaduangratana
C
C
Kotchabhakdi
N
N
Wichyanuwat
P
P
Casalotti
S O
SO
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D003080:Cold Temperature / Q000009:adverse effects; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013315:Stress, Psychological / Q000378:metabolism*; D013550:Swimming
D000893:Anti-Inflammatory Agents; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D003907:Dexamethasone; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases