Two-Dimensional Model of Tissue Oxygen Gradients in Avian Growth Cartilage

Abstract

The avian growth plate cartilage provides an appropriate model for the study of oxygen supply to tissue. Unlike cardiac or skeletal muscle, which have been the classical organs to study oxygen diffusion (Krogh), the cartilage is non-contractile and vessels are confined to sparsely spaced channels which traverse the growth plate longitudinally. Thus, because of the tissue constraints, this organ is incapable of opening new vascular channels during adaptation to oxygen stress. Oxygen stress is a probable concomitant of the growth plate environment. First, because of the low priority of blood flow to the bone (current estimates are that 3% of total body blood flow traverses the entire skeleton) (Tothill). Secondly, cartilage cells are far removed from vascular channels compared to cells in other organs. The average intervascular distance in hypertrophic cartilage (near the mineralization front) is 318 μm, and in resting cartilage (near the articular side of the growth plate) this distance is increased to 404 μm (Silverton 1989b). Measurements of oxygen pressures by glass microelectrode in growth plates are recorded at 20–25 mm Hg (Brighton).