The effects of ischemia on long bone vascular resistance

Abstract

An in vitro canine tibia model was used to assess the effects of 48 h of hypothermic (4 degrees C) ischemia on bone vascular resistance and on responsiveness of intraosseous blood vessels to circulating norepinephrine. Three groups of bones were studied: Group I (n = 11), 48 h hypothermic ischemia; Group II (n = 11), 48 h hypothermic ischemia with pretreatment with allopurinol and oxypurinol; and Group III (n = 10), no ischemia. Resting vascular resistance in both ischemic groups (79 and 74 mmHg/ml/min) was significantly higher (p less than 0.0001) than in the nonischemic group (22 mmHg/ml/min). Effects of norepinephrine on vascular resistance were significantly greater in both ischemic groups (p less than 0.004). In all three groups, acetylcholine infusion attenuated the increases in perfusion pressure caused by norepinephrine. This demonstrates secretion of endothelial-mediated relaxing factors (EDRF) and prostaglandin for up to 48 h of hypothermic ischemia. As no significant differences were detected between the two ischemic groups, this study failed to demonstrate any protective effect of xanthine oxidase inhibitors.

Vasoconstrictive action of neuropeptide Y in Bone: The porcine tibia perfused in vivo

“…The present study in pigs verifies that the infusion of norepinephrine into the tibia1 nutrient artery enhances the hone perfusion pressure, as previously shown in vitro and in vivo (Brinker et al 1990, Davis andWood 1991). However, our threshold concentration of NE seems higher than that observed in previous studies on bone and other organs (Corder et al 1987, Davis andWood 1991). The discrepancies may be ascribed to variations in mode of administration and tissue sensitivity.…”

“…The postsynaptic receptors mediating the excitatory responses of arterial vasoconstriction in bone belong to the alpha-receptor group. NE is known to have specificity for alpha, and alpha2 receptors in various organs, including bone (Davis and Wood 1991). Interestingly, the vasoconstriction in cats, elicited by the injection of NPY, has been shown to be resistant to alpha-adrenergic receptor blockade (Lundberg and Tatemoto 1982).…”

The Effects of Cigarette Smoking on Rabbit Tibial Vascular Endothelium

“…12,13 The optimal flow rate of rabbit tibia model was determined to be 0.3-0.4 ml/min, and was proportional to the weight of tibia. 1,2,12 The OFR of rabbit tibia determined in this investigation is approximately 14% of that in the canine tibia, which typically range from 2.5 to 3.0 ml/min. This relationship is identical in proportion to the average weight of the New Zealand white rabbits, and mongrel dogs used previously.…”

“…Several researchers have used in vivo models to investigate the anatomy and physiology of the osseous microcirculation. [1][2][3][4][5] However, in vivo evaluations do not permit complete control over the wide spectrum of variables such as temperature, blood flow, pH, P O2 , and P CO2 , which may influence vascular smooth muscle contractility.…”

“…In general, intraosseous endothelial cells have similar properties to those of arteries in other organs. [1][2][3][4][5] The vascular response in bony vascular endothelium to many situations, such as acidosis, thrombosis, ischemia, and infection, are similar to those of other organs and are predominantly determined by the blood vessels themselves. [6][7][8][9][10][11] Previous studies about the intraosseous endothelial functions have used a canine tibia model, and have been very helpful for understanding the microvascular changes germane to free vascularized bone transfer.…”