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Published on: July 27, 2009
Detection and quantitation of pro-opiomelanocortin mRNA in pituitary and brain tissues from different species
Abstract:
Pro-opiomelanocortin-like mRNA has been detected in anterior and neurointermediate lobes of the pituitary, hypothalamus, amygdala, and cerebral cortex of rats by Northern blot analysis using a 144-base-pair DNA hybridization probe complementary to the beta-lipotropin domain of pro-opiomelanocortin mRNA. The hybridizing species of RNA in the pituitary lobes and hypothalmus is approximately 1100 bases long whereas that in the amygdala and cerebral cortex is 1000 bases long. Solution hybridization analysis with this same probe indicates that pro-opiomelanocortin mRNA is 20 times as concentrated in the neurointermediate lobe as in the anterior lobe of the pituitary. In turn, the pro-opiomelanocortin mRNA levels in the anterior pituitary are 1 to 2 orders of magnitude higher than those in the brain tissues. These results support the hypothesis that adrenocorticotropic hormone/endorphin peptides previously detected in the hypothalamus and amygdala with immunological techniques are synthesized in these tissues from a precursor similar to pro-opiomelanocortin in the pituitary.
Insights
Pro-opiomelanocortin-like mRNA is present in rat pituitary, hypothalamus, amygdala, and cerebral cortex. This suggests these brain regions may synthesize similar precursor proteins for hormone production.
Area of Science:
- Neuroscience
- Molecular Biology
- Endocrinology
Background:
- Pro-opiomelanocortin (POMC) is a precursor protein for various peptide hormones.
- Previous studies detected POMC-related peptides in the hypothalamus and amygdala using immunological methods.
Purpose of the Study:
- To investigate the presence and distribution of pro-opiomelanocortin-like mRNA in rat brain and pituitary.
- To determine if brain tissues synthesize POMC-like precursors.
Main Methods:
- Northern blot analysis using a specific DNA probe for POMC mRNA.
- Solution hybridization to quantify mRNA levels.
Main Results:
- POMC-like mRNA detected in rat pituitary (anterior and neurointermediate lobes), hypothalamus, amygdala, and cerebral cortex.
- Two distinct mRNA sizes (1100 and 1000 bases) were observed in different tissues.
- Neurointermediate lobe had 20x higher POMC mRNA than the anterior pituitary.
- Anterior pituitary POMC mRNA levels were significantly higher than in brain tissues.
Conclusions:
- The presence of POMC-like mRNA in the hypothalamus and amygdala supports the hypothesis of local synthesis of POMC-like precursor peptides.
- These findings indicate that POMC-related peptides detected immunologically in the brain may be synthesized in situ.
