Consistency and Variance in Human Saliva 2-D Proteome

For future comparative clinical proteomics studies on human saliva it is important to know the baseline variance within the proteome maps derived from one individual at different time points compared to that from different individuals. Objectives: To investigate the inter-individual and intra-individual extent of variance among 2-D protein maps of whole human saliva (WS) as well as of parotid and submandibular/sublingual (SMSL). Methods: For comparison of intra-individual variations, whole, parotid and SMSL saliva were collected from one individual on three different days. For comparison of inter-individual differences, WS and glandular secretions were collected from four different individuals (two male, two female). Salivary proteins were subjected to isoelectric focusing followed by SDS-PAGE over a pH range from 3-10. Spot patterns were visualized by Coomassie-blue stain. Results: A comparison of 2-D gels derived from samples of one individual collected at different days showed a good reproducibility of the overall spot pattern of WS that was even better when comparing that of pure glandular secretions. When comparing 2-D gels of saliva from different individuals, a consistency of most major spots was apparent. Nevertheless, quantitative differences, most prominently for albumin, were noted when comparing the spot patterns of WS. These differences were considerably less pronounced when comparing the spot patterns of glandular secretions from different individuals. The greatest qualitative differences were observed for the spot pattern of acidic proline-rich proteins. Conclusions: Under normal conditions, the intra-individual consistency of 2-D spot patterns observed in this study provides a sufficient basis for future clinical comparative proteome studies exploiting human saliva as a diagnostic fluid. Supported by DFG grant SFB 585/B5