PTHrP
PTHrP, PTH related Protein, exists in the forms of three proteins of approximately 150 amino acids resulting from the hydrolysis of a prehormone by convertases. The first 34 amino acids of PTHrP are almost identical to those of PTH.
Metabolism
PTHrP is synthesized in various normal and malignant tissues: bone, cartilage, smooth muscles, mammary gland, skin, pancreas, placenta, parathyroid glands. The mechanisms controlling its secretion are not well known.
Effects
The effects of PTHrP on bone and kidney are quite similar to those of PTH. But because of its local secretion in many organs, it has specific effects. It induces formation of cartilage by stimulating the proliferation of chondrocytes, the development of mammary gland, calcium transfer in milk and through the placenta. It elicits a relaxation of smooth muscle, in particular vascular.
PTHrP has pathological effects: secreted in large quantity by certain tumors, it is responsible of the hypercalcemia observed in many patients with cancer.
Antagonists of PTHrP are under development and could be useful to treat this type of hypercalcemia.
|
