Objective To investigate the effect of angiotensin-converting enzyme inhibitor (ACEI) captopril on bone loss and kallikrein-kinin system (KKS) in ovariectomized (OVX) osteoporotic rats. Methods Postmenopausal osteoporosis rat model was established using ovariectomy. The rats were divided into OVX group, ACEI group (6 mg/kg×d captopril), positive control estrogen group (0.05 mg/kg×d diethylstilbestrol), and sham group without ovariectomy. After 8 weeks of administration, the levels of serum calcium (CA), procollagen I N-terminal peptide (PINP), alkaline phosphatase (ALP), osteocalcin (OCN), tartrate resistant acid phosphatase (TRAP), and C-terminal telopeptides of type I collagen (β-CTX) were detected with automatic biochemical analyzer. Bone mineral density and microstructure were measured with micro CT. The number of osteoclasts was measured with TRAP method. The protein expressions of bone morphogenetic protein 2 (BMP2), Runt related transcription factor 2 (Runx2), kalli-krein (KLK), bradykinin receptor 1 (B1R) and bradykinin (BK) were detected with Western blotting. Results Compared with those in sham group, BMD, number and thickness of trabeculae, bone volume fraction, SMI, PINP, ALP, OCN levels, BMP2 and Runx2 protein expressions were significantly lower in OVX group (all P<0.05), and trabecular separation, TRAP, and β-CTX levels, osteoclast number, KLK, B1R, and BK protein levels were higher (all P<0.05). Compared with those in OVX group, BMD, number and thickness of trabeculae, bone volume fraction, SMI, PINP, ALP, and OCN levels, BMP2 and Runx2 protein expressions were significantly higher in ACEI group and positive group (all P < 0.05), and trabecular separation, TRAP and β-CTX levels, osteoclast number, KLK, B1R, and BK protein levels were lower (P<0.05). Conclusion ACEI inhibits KKS system, reduces osteoclast activity, reduces bone resorption, enhances osteoblast activity, increases bone formation, increases bone mineral density, improves bone microstructure, and relieves osteoporosis symptoms in OVX rats. |