DIHYDROTESTOSTERONE (DHT) STIMULATES BRANCHING MORPHOGENESIS IN EMBRYONIC LUNG EXPLANTS. ▴ 361

Abstract

DHT affects late gestation lung development by increasing the proliferation of fibroblasts and Type II cells and delaying surfactant production. Based on these findings, it has been suggested that DHT prolongs late gestation (fetal) lung growth resulting in males having larger lungs than females. We postulated that DHT also affects the early gestation (embryonic) lung growth and morphogenesis. We tested this hypothesis by examining the effect of DHT on branching morphogenesis and thymidine incorporation into DNA in embryonic day 11 1/2 mouse lung explants. Lungs were cultured for 72 hours in serum free BGJb medium with either 10-8M DHT or an equal volume (10 μl/ml) of diluent as control. Branching morphogenesis was evaluated at 0, 24, 48, and 72 hours by counting the total number of terminal buds of the left lung under light microscopy. These evaluations were done without knowledge of treatment group. At 48 hours 3H-thymidine (1μCi/ml) was added to all cultures. At 72 hours lung explants were harvested and thymidine incorporation into DNA was determined. The number of terminal buds was similar in the two groups at time zero. Thereafter, the number of terminal buds in the DHT treated group was significantly increased compared to control at 24 hours (DHT: 6.3±0.7 buds; Control: 4.0±0.4 buds; mean±SEM, P=0.006), at 48 hours (DHT: 10.8±0.7; Control 6.4±0.6, P=0.0001), and at 72 hours (DHT: 16.5±1.7; Control 11.1±1.1, P=0.01). The velocity of terminal bud formation, defined as the increase in buds within a given lung over time, was significantly greater in the DHT treated group for the time intervals of zero to 24 hours (DHT: 2.6±0.5; Control: 1.1±0.3; mean±SEM, P=0.02), zero to 48 hours (DHT: 7.1±0.6; Control: 3.5±0.7, P=0.0008), and zero to 72 hours (DHT: 12.8±1.3; Control: 8.2±1.2, P=0.01). Thymidine incorporation into DNA between 48 and 72 hours was decreased in DHT treated lungs (DHT 76%±15% of control; mean±SEM). These data suggest that DHT increases the early velocity of terminal bud formation in the embryonic lung. We speculate that DHT has divergent effects on the growth of airway epithelium versus mesenchymal tissue in embryonic lung, resulting in increased terminal bud formation but decreased overall thymidine incorporation. Supported by HL37930