Fig. 4.

Avpr1α regulates osteoclast formation and function. Genetic deletion of Avpr1α in Avpr1α^−/− mice causes a dramatic reduction in osteoclastogenesis in bone marrow and spleen cell cultures (A), which is accompanied by a reduction in the expression (quantitative PCR) of differentiation genes, namely Cfms, Rank, Nfatc1, and Int β₃ (B), and by a reduction in bone resorption by mature osteoclasts plated on dentine slices (von Kossa-stained) (C). Gain-of-function experiments evaluating the stimulatory effect of AVP injections (4 µg per mouse, twice, 6-wk-old mice killed 12 h after second injection) on TRAP-positive osteoclast formation in bone marrow cell cultures treated with Rankl (30 ng/mL) (D), and on osteoclast genes, namely Cfms, Rank, Trap, Int β₃, Calcr, Ctsk, Clc7, and Atpase6 (E). Statistics by Unpaired Student t test; **P < 0.01 vs. vehicle (−, no AVP) treated at 3 and 7 d of culture. (Magnification: A, Upper, and D, 10×; A, Lower, and C, 2×.)