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Phosphoinositide turnover during hepatocarcinogenesis induced by N-nitrosodiethylamine
S Choudhury1, M Krishna, R K Bhattacharya
1Radiation, Biology and Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
Abstract:
The metabolism of phosphatidylinositol (PI) has been examined in rat liver during administration of N-nitrosodiethylamine (NDEA). The activities of PI kinase and PIP kinase were observed to be decreased as early as 7 days from the onset of NDEA administration, and remained suppressed until 60 days. PI synthetase showed a transient increase in activity at 7 days and thereafter the activity declined. The level of diacylglycerol (DAG), a key second messenger, showed a steady rise during the period of NDEA administration. A parallel increase in DAG kinase activity was also apparent. The results suggest that alterations of enzymes central to second messenger system with resulting changes in phosphoinositide turnover are important events during hepatocarcinogenesis induced by NDEA.
Insights
This study reveals that N-nitrosodiethylamine (NDEA) alters phosphatidylinositol (PI) metabolism in rat liver, affecting key enzymes and second messengers during cancer development. These changes in phosphoinositide turnover are crucial events in NDEA-induced hepatocarcinogenesis.
Area of Science:
- Biochemistry
- Hepatology
- Carcinogenesis
Background:
- Phosphatidylinositol (PI) metabolism plays a critical role in cellular signaling.
- Altered PI metabolism is implicated in various disease states, including cancer.
- N-nitrosodiethylamine (NDEA) is a known hepatocarcinogen.
Purpose of the Study:
- To investigate the impact of NDEA administration on PI metabolism in rat liver.
- To identify specific enzymatic changes and second messenger alterations during NDEA-induced hepatocarcinogenesis.
Main Methods:
- Rats were administered NDEA over a 60-day period.
- Enzyme activities including PI kinase, PIP kinase, PI synthetase, and diacylglycerol (DAG) kinase were measured.
- Levels of DAG, a key second messenger, were quantified.
Main Results:
- PI kinase and PIP kinase activities decreased significantly within 7 days of NDEA administration and remained suppressed.
- PI synthetase activity showed a transient increase at 7 days, followed by a decline.
- Diacylglycerol (DAG) levels and DAG kinase activity increased steadily throughout the NDEA administration period.
Conclusions:
- NDEA administration significantly disrupts phosphatidylinositol metabolism in rat liver.
- Alterations in enzymes central to the second messenger system and phosphoinositide turnover are key events in NDEA-induced hepatocarcinogenesis.
- These metabolic changes may contribute to the development of liver cancer.