Optimized lymphocyte protein extraction performed simultaneously with DNA and RNA isolation: Application to the study of factors affecting DNA, RNA, and protein recovery from lymphocytes of the oldest individuals

We describe an optimized procedure for protein extraction performed simulta neously with that of DNA and RNA from a single tissue sample that is, unlik e the original protocol, suitable for quantitative studies. This optimized protocol is particularly well adapted to studies where gene regulation at D NA, RNA, and protein levels must be examined simultaneously, and when the a mount of starting biological material is limited. We applied this procedure to the study of factors affecting both qualitatively and quantitatively th e extraction of DNA, RNA, and proteins from lymphocytes of very old individ uals, since we observed variability in the recovery of these molecular spec ies with advanced age. Therefore, we investigated the combined effects of a ge and time delay between blood collection and lymphocyte isolation on the recovery of DNA, RNA, and proteins simultaneously extracted from Danish non agenarians and centenarians versus younger adult samples. Our results sugge st that neither RNA nor DNA nor protein contents of lymphocytes are altered with aging. However, the quantity of RNA and protein recovery is affected by a 24-h delay in blood processing. This effect is more pronounced in the oldest, particularly for RNA, and may affect data interpretation of age-dep endent gene expression studies. (C) 1999 Academic Press.