Distribution of prothymosin alpha in rat tissues.

Abstract

A radioimmunoassay, using a rabbit antiserum directed against thymosin .alpha.1, was employed to detect the presence of cross-reacting peptides in rat tissues. Highest concentrations were present in thymus, but thymosin .alpha.1 cross-reacting material was also detected in brain, liver, kidney, lung and spleen, in amounts ranging from 15 of 65% to the quantities found in thymus. In each case, the mjaor immunoreactive peptide, after extraction and purification by a procedure that avoids proteolytic modification, was identified as prothymosin .alpha., a peptide containing .apprxeq. 112 amino acid residues. Prothymosin .alpha. is believed to be the endogenous peptide from which thymosin .alpha.1 and other fragments are formed by proteolytic modification during the preparation of thymosin fraction 5. No peptides corresponding in size and chromatographic behavior to thymosin .alpha.1 were detected with the extraction procedure employed.