The Ca2+-Transporting Activity of Rat Liver Microsomes in Response to Protein Undernutrition: Implications for Liver Tumor Promotion

Abstract

The effect of protein undernutrition on the activity of the smoothendoplasmic reticulum (microsomal) Ca2+-ATPase (SERCA) wasinvestigated. After 12 weeks of ad libitum ingestion of low proteindiet (5% protein), a significant depression (p<0.05) of liver ERCa2+-ATPase activity (68.6% depression) was observed. However,no significant effects on cytochrome P450 activity and relative liverweight were found. It is proposed that low protein diet by inhibitingthe rat liver SERCA activity, might increase the cytosolic free calciumion concentration ([Ca2+]) and promote the development of livertumor. The possible mechanisms of low protein diet induced inhibition ofSERCA activity are highlighted.