Immunohistochemicaf evidence of parathyroid hormone—related protein in human parathyroid tissue

Immunohistochemical staining for parathyroid hormone-related protein (PTHrp) was investigated on cryosections of 17 normal-sized human parathyroid glands, 47 adenomatous and hyperplastic glands of hypercalcemic patients with primary or uremic hyperparathyroidism, and 5 metastases of parathyroid carcinoma. Utilizing a polyclonal antiserum recognizing aminoterminal PTHrp, approximately two-thirds of the normal and enlarged glands but none of the parathyroid carcinomas demonstrated a conspicuous immunostaining. The extent and intensity of the reactivity varied between the glands even of individual patients. The staining was found in chief and oxyphilic parathyroid cells, and studies of cell suspensions substantiated that the immunoreaction was present also on the surface of the parathyroid cells. Reduced PTHrp expression in the functionally more dedifferentiated parathyroid tissue was suggested by comparison of the normal (i.e., suppressed) and adenomatous parathyroid tissue from the individual patients and by parallel stainings with the monoclonal El1 antibody, which recognizes a calcium sensor involved in the regulation of parathyroid hormone release. The findings substantiate a functional role for PTHrp in euparathyroid and hyperparathyroid individuals.