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Ontogeny of Parathyroid Hormone-Related Protein in the Ovine Parathyroid Gland^*

RICHARD J. MACISAAC, IVAN W. CAPLE, JANINE A. DANKS, HANNELORE DIEFENBACH-JAGGER, VIVIAN GRILL, JANE M. MOSELEY, JUSTINE SOUTHBY and T. JOHN MARTIN

St. Vincent's Institute of Medical Research Fitzroy, Victoria, 3065
Department of Veterinary Science, University of Melbourne Werribee, Victoria, 3030, Australia

Address all correspondence and requests for reprints to: Dr. Richard J. Maclsaac, St. Vincent's Institute of Medical Research, Fitzroy, Victoria 3065, Australia.

Abstract

PTH-related protein (PTHrP) has been implicated in calcium regulation during fetal life. In this study the ontogeny of PTHrP was examined in ovine parathyroid glands. Immunohistochemical techniques, Western blot analysis, and a RIA with antisera raised against synthetic fragments of human (h) PTHrP (i.e. 1–34, 1–40, 50–69, and 107–141) were used to detect the presence of immunoreactive PTHrP in parathyroid glands from fetal and neonatal lambs and maternal ewes. Positive immunostaining for PTHrP was observed in fetal (from 116 days of gestation) and lamb (up to 180 days post birth) but not maternal parathyroid glands with the PTHrP(50–69) antiserum. Fetal and lamb parathyroid glands consisted entirely of one cell type in which PTHrP immunoreactivity to PTHrP(50–69) antiserum was found. In contrast, immunoreactivity to PTHrP could not be detected in sections of fetal, lamb, or maternal parathyroid glands with antisera raised against PTHrP(1–34) or PTHrP(107–141). However, PTHrP immunoreactivity in urea/acid extracts of newborn lamb parathyroid glands could be detected by Western blot analysis and RIA with antisera raised against the N-terminal portion of PTHrP. Western blot analysis with the PTHrP(1–34) antisera revealed that urea/acid extracts of newborn lamb parathyroid glands contained a substance with a mol wt of 14.4K, which corresponded in size to that of hPTHrP(1–84). Newborn lamb parathyroid glands contained 0.35 ng PTHrP/µg extract, whereas maternal parathyroid glands contained only 0.035 ng PTHrP/µg extract when tested in a RIA employing recombinant hPTHrP(1–84) as standard and an antibody raised against hPTHrP(1–40). The detection of immunoreactive PTHrP in the developing ovine parathyroid gland provides further evidence to support the suggestion that PTHrP produced in the parathyroid gland is involved in the normal hormonal regulation of calcium metabolism in the mammalian fetus and neonate.

Footnotes

^* This work was supported by grants from the National Health and Medical Research Council, the Anti-Cancer Council of Victoria, and the Wool Research Trust Fund of the Australian Wool Corporation.

Recipient of a National Health and Medical Research Council Australian Postdoctoral Fellowship.

Received February 7, 1991.

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