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Developmental changes and regional distribution of phospholipase D and base exchange enzyme activities in rat brain
M Kobayashi1, D G McCartney, J N Kanfer
1Department of Biochemistry, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Insights
Phospholipase D (PL-D) and 3 base exchange enzyme (BEE) activities show distinct developmental patterns in rat brain regions. Hippocampal PL-D peaks early, while hypothalamic PL-D develops later, differing from BEE activity distributions.
Area of Science:
- Neuroscience
- Biochemistry
- Developmental Biology
Background:
- Phospholipase D (PL-D) and 3 base exchange enzyme (BEE) are enzymes with crucial but not fully understood roles in brain development.
- Understanding the developmental trajectory and regional distribution of these enzyme activities is key to elucidating their functions in neural maturation and function.
Purpose of the Study:
- To investigate the developmental changes and regional distribution of Phospholipase D (PL-D) and 3 base exchange enzyme (BEE) activities in the rat brain.
- To compare the distinct developmental patterns and spatial localization of PL-D and BEE activities across different brain regions.
Main Methods:
- Measurement of PL-D and BEE enzyme activities in whole rat brain homogenates across different postnatal ages (E17 to P30).
- Fractionation of brain homogenates to analyze subcellular distribution of enzyme activities.
- Regional analysis of PL-D and BEE activities in 7 distinct brain regions from postnatal day 1 to 25 months in rats.
Main Results:
- PL-D activity significantly increased from embryonic day 17 to postpartum day 14, with specific increases in P2 and P3 fractions, followed by a slight decrease by P30.
- BEE activity increased up to P14 or P21 and then decreased, with greater reduction in P2 fraction, while P3 fraction activity increased post-P14.
- In adult rats, the hippocampus and hypothalamus showed highest PL-D activity, whereas cerebellum and medulla+pons had the lowest. Hippocampal PL-D peaked early (P7) and declined, suggesting region-specific developmental timing. BEE activity distribution differed, with the cerebellum showing the highest activity in adults and a steep increase from P1.
Conclusions:
- PL-D and BEE enzymes exhibit distinct developmental profiles and regional specificities within the rat brain.
- The hippocampus and hypothalamus display unique developmental patterns for PL-D activity, indicating region-specific regulatory mechanisms.
- These findings provide a foundational understanding of the spatiotemporal regulation of PL-D and BEE during brain development, potentially informing research on neurological disorders.
Abstract:
Phospholipase D (PL-D) activity per mg protein of whole homogenate increased 5.1 fold between Embryonic (E) day 17 and Postpartum (P) day 14 and slightly decreased by P 30 days. This was due to the decrease of PL-D activity of the P2 fraction. The PL-D activity of P2 and P3 fractions increased 11.2 and 6.1 fold respectively between E 17 and P 14. The 3 base exchange enzyme (BEE) activities per mg protein of whole homogenate increased up to P 14 or P 21 and then decreased. This decrease was greater in the P2 fraction and the P3 fraction increased after P 14. Brains from 1 day to 25 month old rats were dissected into 7 separate regions and both PL-D and BEE activities were measured. In adult rats, the hippocampus and hypothalamus had the highest PL-D activities while medulla + pons and cerebellum had the lowest PL-D activities. The developmental patterns of 5 regions except for hippocampus and hypothalamus were similar. PL-D activity in the hippocampus was maximum at P 7 followed by a steep decrease till P 30 suggesting that the PL-D activity of the hypothalamus develops later and that of the hippocampus develops earlier than any other region. The distributions of BEE activities were quite different from those of PL-D activities. In adult rats, the cerebellum had the highest activity while the striatum and medulla + pons had the lowest. The BEE activities of cerebellum were lowest at P 1 and showed steep increase during the next 2 weeks.