Isolation, characterization and synthesis of α-foetoprotein from neonatal-rat skin

Monospecific anti-[rat α-foetoprotein(α-FP)] immunoglobulin G was coupled to CNBr-activated Sepharose-4B (4.5 mg/ml packed volume to gel) to yield an adsorbent. The immunoaffinity column was used to isolate α-FP from neonatal-rat skin. Purified skin α-FP was found to be immunologically and electrophoretically similar to serum α-FP. It yielded a single band with mol.wt. 68,000 on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. However, an polyacrylamide-gel electrophoresis under non-denaturing conditions, the α-FP displayed slow- and fast-moving variants similar to those observed in serum α-FP. A Scatchard plot of oestradiol binding to the α-FP yielded an association constant of 2.5 x 10⁹ M^-1 by dextran-coated-charcoal and 0.75 x 10⁸ M^-1 by Sephadex-gel-filtration procedures respectively. Skin explants from newborn rats were found to incorporate [¹⁴C]leucine into immunoprecipitable intracellular α-FP. Cycloheximide inhibited the synthesis of α-FP in skin explant culture. Our results indicate that newborn-rat skin contains α-FP that is similar to serum α-FP and which may arise in neonatal-rat skin as a result of synthesis in situ.