IMMUNOREACTIVITY AGAINST ANTI-GROWTH HORMONERELEASING HORMONE (GHRH) SERA IN HUMAN PANCREAS AND PANCREATIC ENDOCRINE TUMORS: EVIDENCE OF PITFALL IN IMMUNOHISTOCHEMICAL STUDY

Localization of growth hormone-releasing hormone (GHRH) in normal human pancreas was examined immunohistochemically with four different anti-GHRH sera. Antisera raised aginst synthetic human GHRH(1-40)OH and GHRH(1-29)Gly4-Cys-NH2 gave no positive immunoreaction. Two other antisera (RG107 and #4676) raised against synthetic human GHRH(1-44)NH2 reveal GHRH-like immunoreactivity in pancreatic polypeptide (PP) cells, but the iminunoreactivity was abolished when RG107 or #4676 was absorbed by synthetic human PP(1-36)NH2- Among sixteen pancreatic endocrine tumors, only one tumor from an acromegalic patient contained many cells that reacted with all four anti-GHRH sera; this immunoreactivity disappeared by the addition of synthetic GHRH(1-44)NH2 but not of PP(1-36)NH2- The remaining fifteen tumors, which included eleven PP-positive tumors, did not show any immunoreactivity against the four anti-GHRH sera. The findings suggest that the anti-GHRH-44 sera (RG107 and #4676) contain not only an antibody for GHRH but also antibody that recognizes PP or an antibody that recognizes both GHRH and PP, and also that cells with genuine GHRH immunoreactivity are absent in normal human pancreas. In addition, it is suggested that the molecular structure of PP in normal pancreas differs from that in pancreatic endocrine tumors.