Membranes of Normal Hamster Lymphocytes and Lymphoid Cells Neoplastically Transformed by Simian Virus 40. I. High-Yield Purification of Plasma Membrane Fragments 1, 2

ABSTRACT-In this first paper of a series comparing the mem-branes of normal lymphocyte populations from male outbred Syr-ian hamsters with those of neoplastic transformants (GD 248) induced by simian virus 40, a method is described for the isola-tion of representative plasma membrane (PM) fragments from both cell types. Multiple criteria were used to monitor the purity and yield of PM material after cell disruption by nitrogen cavita-tion and after membrane fractionation by a combination of differ-ential centrifugation and isopyknic ultracentrifugation in dextran density gradients. Lactoperoxidase-catalyzed radioiodination be-fore cell disruption was used as an extrinsic surface marker; Na+,K+-activated ATPase, as well as alkaline phosphatase, was used as intrinsic functional PM markers. The distribution of nu-clei, mitochondria, Iysosomes, and endoplasmic reticulum (ER) during fractionation was monitored by the measurement of DNA