Effects of Rat Alpha-2 Macroglobulin on Growth in vitro

Abstract

The patterns of cellular development of primary explants from four tissues from 18-day rat embryos and of Walker 256 carcinosarcoma have been examined in the presence of rat alpha-1 macroglobulin (A1MG), alpha-2 macroglobulin (A2MG), bovine serum albumin (BSA) and of antisera to the foregoing. The following principal results were obtained: 1. A2MG suppresses the formation of cellular carpets around Walker 256 explants whereas, in all other media tested, the neoplastic tissue showed more frequent cellular carpet formation than the embryonic tissues. 2. A1MG increases the frequency of carpet formation by embryonic tissues relative to the other proteins or to control in plain Medium 199. 3. In each of the tested media, embryonic tissues develop peripheral fibroblasts more often than do neoplastic tissues. 4. In cultures of embryo limb explants, and to a lesser degree with other embryonic tissues, A1MG increased and anti-A1MG decreased the extent to which fibroblasts organize into strands and cords. It is suggested that the suppression of cellular carpet formation by A2MG around Walker 256 explants, but not around embryonic tissue explants, may be related to the peculiar pattern of appearance of this protein in rat sera.