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Acid lipase activity in neonatal rat liver cell types. Effect of starvation
F Burgaya1, M Llobera, I Ramírez
1Department de Bioquimica i Fisiologia, Facultat de Biologia, Universitat de Barcelona, Spain.
Insights
Neonatal rat liver exhibits significantly lower acid lipase activity compared to adults, primarily localized in hepatocytes. This difference normalizes when adjusted for protein content, unaffected by starvation.
Area of Science:
- Biochemistry
- Cell Biology
- Developmental Biology
Background:
- Acid lipase plays a crucial role in cellular lipid metabolism.
- Understanding its activity during early development is essential for metabolic research.
- Hepatic acid lipase activity differences between neonatal and adult mammals are not well-characterized.
Purpose of the Study:
- To investigate the acid lipase activity in the liver of neonatal rats.
- To compare neonatal hepatic acid lipase activity with that of adult rats.
- To determine the cellular distribution and protein-normalized activity of acid lipase in neonatal livers.
Main Methods:
- Enzyme activity assays were performed on whole liver homogenates and isolated hepatocytes and hemopoietic cells from neonatal and adult rats.
- Acid lipase activity was measured using a standard spectrophotometric method.
- Protein content was determined using the Bradford assay.
Main Results:
- Whole liver acid lipase activity in neonatal rats was 50% lower than in adult rats.
- In neonatal livers, acid lipase activity was 7.7-fold higher in hepatocytes compared to hemopoietic cells.
- Neonatal hepatocytes showed approximately 25% of the acid lipase activity found in adult hepatocytes.
- All observed differences in acid lipase activity between neonatal and adult rats disappeared when normalized per milligram of protein.
- Starvation did not significantly alter acid lipase activity in either neonatal or adult rat liver.
Conclusions:
- Hepatic acid lipase activity is significantly lower in neonatal rats compared to adults, with a predominant localization in hepatocytes.
- The developmental decrease in hepatic acid lipase activity is primarily a consequence of lower enzyme levels per cell, not a change in specific activity.
- These findings highlight the distinct metabolic profile of the neonatal liver and are independent of nutritional status.
Abstract:
The acid lipase activity in the liver of neonatal (1-day-old) rats was studied. It was found that (i) in whole liver, the activity was 50% lower than in adult rats; (ii) in neonatal livers, the activity was 7.7-fold higher in hepatocytes than in hemopoietic cells; (iii) neonatal hepatocytes contained about 25% of the activity detected in adult hepatocytes; (iv) all the differences disappeared when expressed per mg of protein; and (v) starvation did not affect the activity either in adult or in neonatal rat liver.