This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Knowles, A. F. Articles by Kaplan, N. O. Search for Related Content PubMed PubMed Citation Articles by Knowles, A. F. Articles by Kaplan, N. O.

Isolation and Characterization of Plasma Membranes from Transplantable Human Astrocytoma, Oat Cell Carcinoma, and Melanomas¹

Department of Chemistry and the Cancer Center, University of California, San Diego, La Jolla, California 92093

Purified plasma membranes were obtained from five transplantable human tumors, a Grade IV astrocytoma, an oat cell carcinoma, and three melanomas. Plasma membrane fractions were isolated from tumor homogenates by differential and discontinuous sucrose gradient centrifugation. Determination of enzyme activities indicated that the plasma membranes were enriched 10- to 20-fold with respect to 5'-nucleotidase, nicotinamide adenine dinucleotide glycohydrolase, Mg²⁺-activated nucleoside triphosphatase, and sialic acid. Specific activities of nearly all the enzymes varied with the individual tumors, even among tumors of the same type, i.e., the melanomas. Electron micrographs of the plasma membrane fractions showed smooth single-membrane vesicles with slight contamination by lysosomes. Therefore, these membranes are suitable for comparative biochemical studies and for the preparation of tumor-specific monoclonal antibodies.

Plasma membranes from all five tumors contained very high Mg²⁺-adenosine triphosphatase (ATPase) activities. The Na²⁺-K⁺-ATPase was a minor component of the total ATPase of these membranes (<30%). The major component was an ATPase exhibiting similar activity toward several nucleoside triphosphates. The activity of such a nucleoside triphosphatase has been correlated with tumorigenicity in cultured liver epithelial cells. The nucleoside triphosphatase of the plasma membranes of astrocytoma and oat cell carcinoma was stimulated from 50 to 100% by concanavalin A, whereas ATPase of the melanoma plasma membranes was not or only slightly stimulated. The different response to concanavalin A could be due to differences in the ATPase molecules of the individual tumors or to the different environment of the ATPase.

¹ This work was supported by grants from the USPHS (CA-11683 and GM-17702), grants from the American Cancer Society (BC-60 and IN-93G), and Athymic Mouse Facility Grant CA-23052.

² To whom requests for reprints should be addressed, at Department of Chemistry, Q-058, School of Medicine, University of California, San Diego, La Jolla, Calif. 92093.

Received 11/17/80. Accepted 7/ 9/81.