Studies from Dr. Hastings' laboratory have identified the amino terminal portion of PTHrP, PTHrP 1-34, as a regulatory factor for alveolar type II cells with striking effects on differentiation and growth. Alveolar epithelial cells secrete PTHrP and express the PTHrP receptor. PTHrP 1-34 causes a dose-dependent increase in the number of lamellar bodies per type II cell and stimulates phosphatidylcholine secretion and synthesis in type II cells and A549 cells. Furthermore, endogenous PTHrP 1-34 inhibits type II cell proliferation. PTHrP levels in lung and air spaces are elevated in human and animal models of lung injury, suggesting that PTHrP may be involved in the response to injury.
References about PTHrP and alveolar type II cells