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Calmodulin antagonist trifluoperazine inhibits polyamine biosynthesis and liver regeneration
R W Alexander1, R Saydjari, D G MacLellan
1Department of Surgery, University of Texas Medical Branch, Galveston 77550.
Abstract:
Polyamines are essential for cell growth and differentiation. Trifluoperazine (TFP) is a potent, competitive inhibitor of the calcium-calmodulin complex. TFP, when given to rats after partial hepatectomy, causes a significant decrease in DNA synthesis. The purpose of this study was to examine the effects of TFP on polyamine biosynthesis and on liver regeneration after partial hepatectomy. TFP (60 mg/kg, bodyweight) or saline control was administered to 80 male Sprague-Dawley rats 2 h before, 2 h after, or at the time of hepatectomy. Polyamines (putrescine, spermidine and spermine) were measured at the time of hepatectomy, and at 6, 24, 48, and 72 h after hepatectomy. TFP, when it was administered either 2 h before or at time of hepatectomy, blocked increases in putrescine that are seen normally at 6 h after hepatectomy. When TFP was given at the time of partial hepatectomy, putrescine was increased at 24 h, and then returned to normal levels at 72 h. Spermidine was inhibited at 24 h, but not at 48 and 72 h. Spermine was not significantly altered at any time. The administration of TFP 2 h after hepatectomy did not significantly alter concentrations of polyamines. The weight of regenerating liver was decreased by TFP at 48 h (23 per cent) and 72 h (22 per cent) after hepatectomy. These findings provide evidence that the calcium-calmodulin complex is required for the synthesis of liver polyamines before liver regeneration can proceed.
Insights
Trifluoperazine (TFP) inhibits polyamine synthesis and liver regeneration after partial hepatectomy by blocking the calcium-calmodulin complex. This suggests the complex is crucial for polyamine production during liver regrowth.
Area of Science:
- Biochemistry
- Cell Biology
- Hepatology
Background:
- Polyamines are vital for cell proliferation and differentiation.
- The calcium-calmodulin complex plays a role in cellular processes.
- Partial hepatectomy is a model for studying liver regeneration.
Purpose of the Study:
- To investigate the impact of Trifluoperazine (TFP) on polyamine biosynthesis.
- To determine TFP's effect on liver regeneration following partial hepatectomy.
- To explore the role of the calcium-calmodulin complex in these processes.
Main Methods:
- Administration of TFP (60 mg/kg) or saline to rats undergoing partial hepatectomy.
- TFP was given at different time points: 2 hours before, at the time of, or 2 hours after hepatectomy.
- Measurement of polyamine levels (putrescine, spermidine, spermine) and liver weight at various intervals post-hepatectomy.
Main Results:
- TFP administration before or at hepatectomy blocked early putrescine increases and inhibited spermidine levels.
- TFP treatment at the time of hepatectomy led to delayed putrescine increase and reduced liver regeneration at 48 and 72 hours.
- TFP administration 2 hours after hepatectomy did not significantly affect polyamine concentrations or liver regeneration.
Conclusions:
- The calcium-calmodulin complex is essential for initiating polyamine synthesis required for liver regeneration.
- Inhibiting the calcium-calmodulin complex with TFP disrupts polyamine biosynthesis and impairs liver regrowth.
- These findings highlight the critical role of calcium-calmodulin signaling in the early stages of liver regeneration.