Reactivity of intraosseous femoral head arteries after long term glucocorticoid treatment: An experimental study in immature pigs

In the pathogenesis of steroid induced femoral head necrosis only intra- and extravascular factors have been discussed. Vasoreactivity of intraosseous femoral head arteries has not previously been investigated. This study investigates the effect of long term glucocorticoid treatment on reactivity of intraosseous femoral head arteries in a porcine model. From 24 immature female Danish Landrace pigs from 12 litters, 12 animals received 100 mg methyl-prednisolone (orally) daily for 3 months. Their 12 sister pigs served as controls and received no corticosteroid. After sacrificing the animal, resistance arteries (diameter approximately 250 µm) were isolated from the femoral head epiphyseal cancellous bone and mounted as ring preparations on a small vessel myograph for measurement of isometric force development. The vasocontractory response to increasing doses of noradrenaline was not altered by methylprednisolone treatment. After submaximal precontraction by noradrenaline, vasorelaxation by sodium nitroprusside was not altered by methylprednisolone treatment. Only part of both experimental groups showed vasorelaxation to substance P and increasing doses of bradykinin. Increasing dose of endothelin-1 evoked vasoconstriction in both experimental groups. Sensitivity to endothelin-1 was increased after 3 months of methylprednisolone treatment. The response of isolated intraosseous femoral head arteries to endothelin-1 after long term glucocorticoid treatment in the pig is enhanced and appears to be unchanged for other physiologic vasoactive substances.Presented in part as a Young Investigator Award Competition of the 42^nd Annual World Congress International College of Angiology, San Diego, California, June 2000.