COMPARISON OF THE LIPID AND APOLIPOPROTEIN COMPOSITION OF SKELETAL-MUSCLE AND PERIPHERAL LYMPH IN CONTROL DOGS AND IN DOGS FED A HIGH-FAT, HIGH CHOLESTEROL, HYPOTHYROID-INDUCING DIET

Most studies of peripheral interstitial fluid lipoprotein composition have been made on interstitial fluid-derived from skin and connective tissue. We developed techniques which allowed simultaneous comparison of lymph (a model of interstitial fluid) from skeletal muscle and skin in control (C) and cholesterol-fed (CF) dogs. Lipoprotein fractions w ere separated by ultracentrifugation. Skeletal muscle interstitial flu id HDL concentrations were approximately twice those of skin. However, the concentration of VLDL-LDL particles was similar in both interstit ial spaces. HDL particles from both microvascular beds showed evidence of extensive remodelling when compared to plasma HDL from the same an imal. Relative to apo A-1, skeletal muscle HDL was enriched in free ch olesterol and apo E (C and CF dogs) and apo A-IV (CF dogs). Skin-deriv ed HDL was consistently enriched in free cholesterol, apo E and A-IV i n both C and CF dogs. These studies indicate that similar remodeling o f plasma HDL occurs in widely different tissues which together constit ute approximately 70% of the total interstitial space. The relatively high concentration of plasma-derived and remodeled HDL within the inte rstitial space of skeletal muscle is consistent with that tissue's imp ortance in reverse cholesterol transport.