This Article Full Text Full Text (PDF) Supplemental Data Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Google Scholar Articles by Stengel, A. Articles by Reeve, J. R. PubMed PubMed Citation Articles by Stengel, A. Articles by Reeve, J. R., Jr.

The RAPID Method for Blood Processing Yields New Insight in Plasma Concentrations and Molecular Forms of Circulating Gut Peptides

CURE Digestive Diseases Research Center, University of California, Los Angeles, and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California 90073

Address all correspondence and requests for reprints to: Joseph Reeve, Jr., Ph.D., University of California and CURE Digestive Disease Research Center, Building 115, Room 117, Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Boulevard, Los Angeles, California 90073. E-mail: JReeve{at}mednet.ucla.edu.

The correct identification of circulating molecular forms and measurement of peptide levels in blood entails that the endocrine peptide being studied is stable and recovered in good yields during blood processing. However, it is not clear whether this is achieved in studies using standard blood processing. Therefore, we compared peptide concentration and form of 12 ¹²⁵I-labeled peptides using the standard procedure (EDTA-blood on ice) and a new method employing Reduced temperatures, Acidification, Protease inhibition, Isotopic exogenous controls, and Dilution (RAPID). During standard processing there was at least 80% loss for calcitonin-gene-related peptide and cholecystokinin-58 (CCK-58) and more than 35% loss for amylin, insulin, peptide YY forms (PYY_(1–36) and PYY_(3–36)), and somatostatin-28. In contrast, the RAPID method significantly improved the recovery for 11 of 12 peptides (P < 0.05) and eliminated the breakdown of endocrine peptides occurring after standard processing as reflected in radically changed molecular forms for CCK-58, gastrin-releasing peptide, somatostatin-28, and ghrelin. For endogenous ghrelin, this led to an acyl/total ghrelin ratio of 1:5 instead of 1:19 by the standard method. These results show that the RAPID method enables accurate assessment of circulating gut peptide concentrations and forms such as CCK-58, acylated ghrelin, and somatostatin-28. Therefore, the RAPID method represents an efficacious means to detect circulating variations in peptide concentrations and form relevant to the understanding of physiological function of endocrine peptides.