The present invention is directed to the use of synthetic thiol-containing peptides as highly effective therapeutic and protective agents 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, the present invention provides 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-P-Ala-His-Cys (SEQ ID NO: 3). The present invention further provides compositions and methods for preserving biological samples using the peptides.
