Use of synthetic thiol-containing peptides as highly effective therapeutic and protective agents is described, in clinical and research applications where lifespan and/or viability and functioning of cells is compromised at least partially due to depletion of reduced glutathione, or where viability and functioning of cells can be improved by elevating reduced glutathione levels. More specifically, compositions and methods for treating blood disorders associated with glutathione dysregulation utilizing short thiol-containing peptides selected from the group consisting of Cys-Lys-Met-Cys (SEQ ID NO: 1), Cys-Met-Lys-Cys (SEQ ID NO: 2) and Cys-β-Ala-His-Cys (SEQ ID NO: 3) are described. Further described are compositions and methods for preserving biological samples using the peptides.
