Geoffrey W. Tregear

Effects on Bone In Vitro of Bovine Parathyroid Hormone and Synthetic Fragments Representing Residues 1–34, 2–34 and 3–34

The biological activities of bovine parathyroid hormone (BPTH) and fragments comprising portions of its amino-terminal sequence have been compared in three different assay systems using embryonic rat bone in vitro. Whereas the 3-34 fragment was without significant activity the 1-34 fragment caused all the actions characteristic of BPTH 1-84, extending to bone previous evidence that the amino-terminal residues are sufficient for expression of the biological effects of intact parathyroid hormone. However, the relative potencies of the fragment and the intact hormone were different in the various systems. BPTH 1-34 showed relatively low osteolytic activity and induced anabolic effects in both osteoblasts and cartilage cells of cultivated embryonic mouse radii which were not evoked by the intact hormone. Further work is required to determine the mechanisms responsible for these interesting alterations in relative potency of fragment and native hormone.

The Chemistry of Parathyroid Hormone and the Calcitonins

Publisher Summary This chapter discusses the chemistry of parathyroid hormone and the calcitonins. In the last several years, there have been striking advances in knowledge of the chemistry of parathyroid hormone and calcitonin. The complete amino acid sequence of the major form of bovine and porcine parathyroid hormone has been determined, and, as well, the complete structure of porcine, human, ovine, bovine, and three different isohormonal forms of salmon calcitonin. These advances are potentially of considerable interest and importance to investigators and clinicians concerned with the physiology, mode of action, and clinical significance of parathyroid hormone and calcitonin. The significance of these chemical advances, particularly the availability of highly potent and completely homogeneous preparations of synthetic parathyroid hormone and calcitonin can best be appreciated in terms of a historical perspective. Intensive physiological and clinical investigations have established the importance of parathyroid hormone in normal calcium homeostasis and in certain diseases involving disorders of calcium and bone metabolism. The hormone acts to increase rates of bone resportion and to reduce the rate of urinary calcium loss, thereby maintaining serum calcium and preventing hypocalcemia.

Radioimmunoassay for Proparathyroid Hormone

A sensitive radioimmunoassay has been developed to bovine proparathyroid hormone which employs an antiserurm produced by immunization of rabbits with a synthetic 18-amino acid peptide fragment of the bovine prohormone. The synthetic prohormone fragment was prepared by solid-phase synthesis and consists of the amino-terminal 12 residues of bovine parathyroid hormone plus the hexapeptide sequence of the bovine prohormone. The antiserum is uniquely specific to detection of the prohormone or synthetic fragments that preserve the peptide linkage between the prohormone region and amino-terminal hormonal sequences. Bovine proparathyroid hormone of natural origin, as well as synthetic fragments incorporating the prohormone hexapeptide sequence and amino-terminal sequences of bovine parathyroid hormone, are bound by the antiserum, but the hexapeptide, intact bovine or human hormone and amino-terminal hormonal fragments alone are not detected. The assay readily measures prohormone in extracts of bovine but not huma...

Synthetic Analogues of Residues 1-34 of Human Parathyroid Hormone: Influence of Residue Number 1 on Biological Potency in Vitro

A biologically active tetratriacontapeptide of human parathyroid hormone, hPTH (1-34), has been synthesized together with a series of structural analogues involving changes at the amino-terminal residue. Acetylation of the terminal amino group results in a marked reduction in the biological potency as measured in the in vitro rat renal adenylyl cyclase assay. Deletion of the terminal amino group results in a loss of biological activity. Substitution of the amino-terminal serine residue with glycine gives a lowered potency whereas substitution with alanine results in a 2-5-fold increase in biological activity in the in vitro assay. The results are compared with the findings previously reported for a series of amino-terminal analogues of the bovine PTH 1-34 peptide.

Parathyroid Hormone: Chemical and Immunochemical Studies of the Active Molecular Species

This chapter discusses the chemical and immunochemical studies of the active molecular species. Bovine parathyroid hormone has been isolated in the form of three homogeneous isohormones and the porcine hormone has also been purified. The presence of hormonal fragments appears to explain the nonparallel responses produced in the radioimmunoassay by hormone in peripheral plasma. It is observed that such nonparallel slopes using one or more antisera in the radioimmunoassay with most peripheral plasma samples tested, while hormone in blood directly from the parathyroid glands has been, without exception, completely parallel with hormone extracted from the glands. One explanation for the nonparallel slopes seen in the radioimmunoassay of parathyroid hormone in peripheral plasma may be the presence in the assay antiserum of two or more antibodies with different antigenic determinants and different affinity constants for the hormone. Thus, when one fragment is present at greater concentrations than the other, a change in displacement slope can be predicted. Alternately, the cleavage of the intact hormone at an important antigenic site of the molecule may change the displacement slopes.

Comparative biochemistry of parathyroid hormone and calcitonin

Abstract This is a brief summary of the current state of our knowledge concerning the chemical nature of parathyroid hormone and calcitonin from several vertebrate species, primarily mammalian. Bovine and porcine parathyroid hormone have been isolated in pure form and their structures analyzed. The complete amino acid suquence of porcine, human, ovine, bovine, and three different isohormonal forms of salmon calcitonin have been determined. Synthesis has been achieved of porcine, human, and salmon calcitonin, and, most recently, the biologically active amino terminal portion of bovine and porcine parathyroid hormone.