Circulatory dissemination of 15-mu particles from the immature rat femur

Venous drainage from the femur of adult animals is not interrupted by occlusion of the blood supply in the soft tissue surrounding the diaphysis of the bone. Previous studies have shown that the metaphyseal drainage system is capable of rapidly transporting particles up to 100 mu in diameter to the lungs. The present study was performed to determine if venous drainage from the femur of immature animals possesses similar characteristics. Three-week-old rats were given a 5-microliters intramedullary injection containing radioactively labeled 15-mu-diameter microspheres. In the intact animal, the particles moved from the injection site in the femur to the lungs within two minutes; however, obliteration of blood flow in the soft tissue surrounding the femoral diaphysis significantly reduced this movement in most animals. The ratio of particles moving through the lungs into the peripheral arterial circulation was slow and similar to that found in adult animals.