Activation of avian medullary bone osteoclasts by oxidized synthetic parathyroid hormone (1-34)

Synthetic bovine parathyroid hormone (1-34) [bPTH(1-34)] has been treated with hydrogen peroxide and assayed for the effect of such treatment on the ability of bPTH(1-34) to activate medullary bone osteoclasts during their quiescent period in the early phase of the ovulatory cycle in Japanese quail. In addition, the same batches of oxidized and unoxidized bPTH(1-34) were assayed for their hypercalcemic activity in Japanese quail and their capacity to stimulate renal adenylate cyclase activity in the same species. Three groups, each consisting of five 5-month-old egg-laying Japanese quail (Coturnix coturnix japonica), were used. Between 4 to 5 hr after oviposition the three groups were injected intraperitoneally with acid saline (control) solution, bPTH(1-34) at 40 micrograms/bird, or oxidized bPTH(1-34) at 40 micrograms/bird, respectively. Twenty minutes after injection, the femoral bones were removed, split, fixed, and appropriately processed for examination by electron microscopy. Both oxidized and unoxidized bPTH(1-34) stimulated the development of osteoclast ruffled borders within 20 min after injection of the hormone preparations. As anticipated from previously published work from this laboratory, oxidized bPTH(1-34) retained its hypercalcemic activity and lost its capacity to stimulate renal adenylate cyclase activity in the Japanese quail. These results support, but do not prove, the contention that bPTH(1-34) exhibits its responses in the Japanese quail through the mediation of more than one type of receptor.