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Vasodilation of femoral PNAs to the PTH analogs occurred via activation of the endothelial cell PTH1R for NO-mediated events. PTH 1-84 and PTHrP 1-34 primarily stimulated PKA signaling, and PTH 1-34 equally stimulated PKA and PKC signaling.

Lameness in broilers can be associated with progressive degeneration of the femoral head leading to femoral head necrosis and osteomyelitis. Femora from clinically healthy broilers were dissected at 7 (n = 35, 2), 14 (n = 32), 21 (n = 33), 28 (n = 34), and 42 (n = 28) d of age, and were processed for bone histomorphometry to examine bone microarchitecture and bone static and dynamic properties in the secondary spongiosa (IISP) of the proximal femoral metaphysis. Body mass increased rapidly with age, whereas the bone volume to tissue volume ratio remained relatively consistent. The bone volume to tissue volume ratio values generally reflected corresponding values for both mean trabecular thickness and mean trabecular number. Bone metabolism was highest on d 7 when significant osteoblast activity was reflected by increased osteoid surface to bone surface and mineralizing surface per bone surface ratios. However, significant declines in osteoblast activity and bone formative processes occurred during the second week of development, such that newly formed but unmineralized bone tissue (osteoid) and the percentages of mineralizing surfaces both were diminished. Osteoclast activity was elevated to the extent that measurement was impossible. Intense osteoclast activity presumably reflects marked bone resorption throughout the experiment. The overall mature trabecular bone volume remained relatively low, which may arise from extensive persistence of chondrocyte columns in the metaphysis, large areas in the metaphysis composed of immature bone, destruction of bone tissue in the primary spongiosa, and potentially reduced bone blood vessel penetration that normally would be necessary for robust development. Delayed bone development in the IISP was attributable to an uncoupling of osteoblast and osteoclast activity, whereby bone resorption (osteoclast activity) outpaced bone formation (osteoblast activity). Insufficient maturation and mineralization of the IISP may contribute to subsequent pathology of the femoral head in fast-growing broilers.

Adequate bone blood flow is requisite for bone growth and repair. Regulation of bone blood vessels via the nervous system may provide a mechanism for the control of bone perfusion. We assessed whether the femoral principal nutrient artery (PNA), the primary conduit for blood flow to long bones, is controlled by various neurotransmitters and neuropeptides. Femoral PNAs from male Wistar rats (4 mon) were dissected and cannulated to assess vasomotor properties to increasing concentrations of neuropeptide Y (NPY; 0.125–1.000 mg/ml), Adenosine triphosphate (ATP; 0.78–50.00 μM/ml), mATP (4.95×10−4 – 4.95×10−8 M), norepinephrine (NE; 10−9–10−4 M), phenylephrine (PE; 10−9–10−4 M), clonidine (CLO; 10−9–10−6 M), vasoactive intestinal peptide (VIP; 10−10–10−4 M), calcitonin gene related peptide (CGrP; 10−10– 10−4 M) and Substance P (Sub P; 10−10–10−4 M). Interestingly, the femoral PNAs vasoconstricted to NPY, ATP and mATP (range = 31–57%). Additionally, vasoconstriction to NE and PE was ~77%, while CLO elicited only 33% vasoconstriction. Peak vasodilatations between 33–54% were observed to VIP, CGrP and Sub P. Data from the current study illustrate a potential role for these neurotransmitters and neuropeptides in the regulation of the bone resistance vasculature. Thus, the nervous system may provide a means of controlling bone blood flow during bone growth and repair. Supported by UTA REP grant 10466.

BACKGROUDLameness in broiler chickens often presents as femoral head separation, degeneration and necrosis. The etiologies of these disorders are unknown and may results from compromised blood flow to femora and/or imbalances in bone resorption and formation.METHODSWe examined developmental changes in femoral bone volume and metabolism, via histomorphometry, at 7, 15, 21, 28, and 42 days. Bone volume (BV/TV, %), osteoid surface (OS/BS, %), osteoblast activity (Ob.S/BS, %) and osteoclast activity (Oc.S/BS) were evaluated.RESULTSBody mass increased 23‐fold from 7 to 42 days. BV/TV remained stagnate (range: 5%–8%) and reached its highest value at day 28. Bone volume‐to‐body mass ratio (range: 0.057%–0.002%), Ob.S/BS (range: 1.3%–0.5%) and OS/BS (range: 22.9%–5.6%) declined significantly (p < 0.05) with age and Oc.S/BS was so excessive throughout development that analysis was not possible. In addition, vast areas of chondrocyte columns often expanded into the secondary spongiosa.CONCLUSIONSDevelopment of broiler femora failed to sufficiently match overall body growth. The lack of bone development corresponded to diminished osteoblast and augmented osteoclast activity. The large chondrocyte columns possibly coincide with a lack of blood vessel penetration that is necessary for calcification of the cartilage template and subsequent bone development. Supported by Cobb‐Vantress Inc.