Direct non-genomic effect of steroid hormones on superoxide anion generation in the bone resorbing osteoclasts

We have investigated the possible acute effect of steroid hormones, including lcr,25 dihydroxycholecalciferol (l alpha,25(OH)(2)D-3) and estradiol, on the generation of superoxide anion (O-2(.-)) in bone resorbing osteoclasts. Evidence is presented demonstrating acute non-genomic stimulatory action of 1 alpha,25(OH)(2)D-3 on the production of free radicals by rat osteoclasts cultured on calcified matrix. The increase in O-2(.-) production was observed in the range of 6-10 s (n = 5) following exposure of enriched osteoclasts to 1 alpha,25(OH)(2)D-3 and was found to be transient with the peak response being in the range of 5-45 s (n = 5). The decline in the transient was much slower than the elevation, time for the decay being in the range 1-5 min (n = 5) and remained above the levels present prior to the addition. The exposure of the osteoclast to dexamethasone was found to have no effect on O-2(.-) generation, whilst estradiol was found to be inhibitory. The mode of stimulation and the kinetics of the transients of O-2(.-) in the bone resorbing osteoclasts produced by 1 alpha,25(OH)(2)D-3 were similar to that of parathyroid hormone (PTH) and pertussis. The exposure of the bone resorbing osteoclasts to cholera toxin was found to have no effect, suggesting that the stimulatory action is unlikely to be mediated via cAMP elevation. The importance of these observations is discussed in the context of calcium homeostasis and bone physiology. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.