Phosphatidylcholine mobility in bile salt depleted rat liver microsomes

Abstract

Rat liver microsomes prepared by differential centrifugation are known to contain measurable levels of bile salts. More than 90% of these can be removed by passing the microsomal preparation through a Bio-Gel A-150m column. Bile salt depleted microsomes show a high level (> 95%) of mannose-6-phosphatase latency. Phospholipid mobilities in normal and bile salt depleted microsomes were compared employing 31P-NMR and phosphatidylcholine-exchange protein. 31P-NMR spectra obtained at different temperatures (between 5 and 37°C) were identical for both microsomal preparations. At 37°C the phosphatidylcholine pool of both preparations appeared to be completely and rapidly available for protein-mediated exchange. These results indicate that bile salts are not responsible for phosphatidylcholine mobility in microsomes.