[3H]HARMALINE AS A SPECIFIC LIGAND OF MAO A–II. MEASUREMENT OF THE TURNOVER RATES OF MAO A DURING ONTOGENESIS IN THE RAT BRAIN |
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Authors: | D L Nelson A Herbet J Glowinski M Hamon |
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Institution: | Groupe NB-INSERM U.114, College de France, 11, place Marcelin Berthelot, 75231 Paris Cedex 05, France |
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Abstract: | The combined measurement of MAO A activity (using 3H]5-HT as a specific substrate) and 3H]harmaline binding capacity indicated that the concentration of MAO A in brain was higher in 14-28 day old rats than in adult animals. The turnover rates of this enzyme in the forebrain and the brain stem of young (14-28 day old) and adult rats were calculated by following the recovery of MAO A activity and of 3H]harmaline binding capacity after an acute treatment with pargyline (75mg/kg i.p.). Both the fractional rate constant for MAO A degradation and its synthesis rate per g of fresh tissue were significantly higher in young animals. However, the calculation of the absolute synthesis rates of MAO A per brain area gave very similar values in young and adult animals: 1.3-1.5 × 1013 molecules of MAO A synthesized per day in the forebrain and 2.3-2.9 × 1012 molecules per day in the brain stern. The results illustrate the validity of using 3H]harmaline binding to evaluate possible changes in the turnover rate of MAO A in tissues. |
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