KSEF RDE: Mass Spectral Analysis of Parathyroid Hormone Peptides from Plasma

Circulating parathyroid hormone (PTH) concentrations are routinely used by nephrologists as a surrogate marker of bone homeostasis, and consequently for making therapeutic decisions for individuals with impaired renal function. Recently, however, the evolution of newer PTH assays has generated significant concerns about the desirable target values of PTH that nephrologists should seek to attain for their patients. Currently, most commercial applications measuring PTH employ a 'sandwich' assay of 2 antibodies directed against different epitopes to isolate and detect the peptide hormone as part of an enzyme-linked immunosorbent assay (ELISA). The newest assays claim to be better at detecting the full-length, intact hormone, heightening confusion about interassay comparisons and whether presumed protelytic fragments not measured with these new assays may yet be clinically significant. Given the uncertainty surrounding the indirect readouts inherent in any ELISA-based system, the current proposal is seeking funds to explore the use of mass spectrometry to profile the population of PTH-derived molecules isolated from plasma samples. We will seek to optimize conditions for the recovery of PTH peptides from plasma using different immunoaffinity approaches that will sufficiently concentrate and purify the peptides for mass spectral analysis. We will then initiate preliminary studies to compare the profile of recovered peptides from normal individuals and with those afflicted with renal insufficiency. This proposal would enable us to collect critical preliminary data to demonstrate the feasibility and usefulness of this analysis, and justify the submission of an expanded study to extramural funding sources.