Effect of insulin on permeability of lysosome membrane in primary monolayer hepatocyte culture of newborn rats under anoxia conditions

Abstract

The influence of insulin was studied in the monolayer hepatocyte cultures of newborn rats during anoxia. Insulin (1.10^-4 U ml^-1) caused a significant increase of acid phosphatase activity in the lysosome-rich subcellular fraction after 20 min exposure of the cells to anoxia and also in experiments in which hepatocytes were incubated with insulin for 1 h in normoxia followed by exposure to anoxia for 20 min. The data obtained suggest that insulin had a stabilizing effect on lysosomal membranes when exposure to insulin was prolonged. On the other hand, insulin caused a more-than 2-fold increase in cAMP content in hepatocytes in a 2 min exposition when compared to control cultures. When exposition of the cells to insulin lasted for more than 2 min, lowering of cAMP content was observed. The data seem to indicate that the stabilizing effect of insulin on lysosomal membrane was secondary to the increase in the cAMP level.

From the above evidence and that accumulated by others we conclude that there may exist an indirect connection between the cAMP level, insulin stabilizing action, and the state of lysosomal membranes.

Key Words:

• acid phosphatase
• anoxia
• cyclic nucleotides
• cell culture
• hepatocyte
• lysosome
• newborn rats