Interaction of androgen and 1,25‐dihydroxyvitamin D 3 : Effects on normal rat bone cells

We studied the actions of testosterone (T) and 5α‐dihydrotestosterone (DHT) in combination with 1,25‐di‐hydroxyvitamin D 3 [1,25‐(OH) 2 D 3 ] on primary rat bone cells. The actions of androgens were generally anabolic, although response patterns varied considerably between cultures. For example, DHT caused striking dose‐ and time‐dependent increases in [ 3 H]thymidine incorporation into calvarial cells over the range 1–100 nM, with maximal stimulation of 2.5‐fold after 9 days in culture. Testosterone (50 nM) also stimulated [ 3 H]‐thymidine incorporation into long bone‐derived cells. 1,25‐(OH) 2 D 3 , generally blunted or abolished the proliferative action of androgens but was not itself always inhibitory; in some experiments, stimulation of [ 3 H]‐thymidine incorporation occurred. Collagen production, as assessed by [ 3 H]proline incorporation into pepsin‐resistant protein secreted by calvarial cells, was also stimulated by DHT. In some cultures, androgen responses were absent, although striking inhibitory responses to 1,25‐(OH) 2 D 3 were observed. These results illustrate complex patterns of responses to androgens and 1,25‐(OH) 2 D 3 in cells derived from rat bone.