Abstract
The structural requirement for full biological activity of parathyroid hormone (PTH), on 84-amino acid single-chain polypetide is satisfied by the 34-amino acid fragment at its NH2-terminal. The procedure to obtain a radioligand with both high specific radioactivity and bioactivity includes a gentle iodination using electrolysis or lactoperoxidase. The sulfur-free analogue [Nle8, Nle18, Tyr34] bPTH (1-34) amide, is stable during the oxidation and is also used as a radioligand. The PTH receptor in plasma membrane of chicken renal cortex is a single component with high affinity to bPTH (1-34), (Kd=7 to 10nM). Guanyl nucleotides stimulate not only PTH dependent adenylate cyclase activity but also the dissociation of 125I-bPTH (1-34) from a plasma membrane of canine renal cortex.
Pseudohypoparathyroidism Type 1 (PHP-1) is an inherited disease characterized by its resistance to stimulation of adenylate cyclase by PTH. The erythrocytes of patients with PHP-1 show partially deficient activity of a guanyl nucleotide regulatory protein that is required for a functional coupling of hormone receptors and catalytic adenylate cyclase. It is also reported, however, that some of the clinically evident PHP-1 patients are possessed of quantitatively and qualitatively normal N-protein activities in erythrocytes. These findings suggest the biochemical and genetic heterogeneity of the disorder classified as PHP-1.
