Plasma membrane fluidity in isolated rat hepatocytes: A comparative study using DPH and TMA-DPH as fluorescent probes

The study of membrane fluidity is a rapidly expanding field of research and its interest in hepatology has been stressed recently. The present study is the first report concerned with the determination of membrane fluidity of isolated rat hepatocytes. The data have been compared with those obtained in plasma membrane fractions and subfractions (basolateral or canalicular) derived from homogenates. The fluorescent probes used to measure the fluidity were diphenylhexatriene (DPH) a 'classical' probe, and its derivative trimethylammoniodiphenylhexatriene (TMA-DPH) at 25 degrees C and at 37 degrees C. The values obtained with DPH were lower than those with TMA-DPH, probably due to the localization of the probes in different regions of the phospholipid bilayer. In addition, DPH revealed significant differences in the fluorescence polarization values obtained in isolated hepatocytes compared with membrane fractions, which was in contrast to TMA-DPH, where the respective values were of the same order of magnitude. This behaviour is probably due to the mobility of DPH in the membrane core and its rapid internalization into the cell, whereas TMA-DPH remains anchored for a long time on the cell surface. These findings suggest that TMA-DPH is a better probe than DPH for measuring the fluorescence polarization of whole isolated hepatocytes and that the use of different probes might be of help in exploring different zones of the membrane bilayer.     

Bone and Marrow Transplants in the Rat

A simple method for transplantation of autologous bone and marrow to therat kidney is described and the usefulness of this preparation for research onbone and marrow growth is pointed out.

While an induction mechanism cannot be conclusively ruled out by thesestudies, the histologic evidence strongly supports the concept that growth ofimplanted bone and marrow is due to survival of small islands of active boneand marrow cells and from these foci, repopulation takes place.

Submitted on March 23, 1961 Accepted on July 6, 1961