CAPILLARY DIFFUSION CAPACITY AND TISSUE DISTRIBUTION OF PANCREATIC PROCOLIPASE IN RAT

The permeability-surface area product of procolipase and its apparent distribution volume in rat tissues were assessed using a tissue uptake technique. Procolipase was investigated together with Cr-51-EDTA, use d as an inert extracellular marker, and I-131-albumin, used as a plasm a volume marker. The tissue uptake of procolipase seemed to occur by p assive transport in most of the organs studied, such as in muscle, liv er, lung, adipose tissue, adrenal glands, colon, and skin. However, th roughout the gastrointestinal tract, except in the colon, there was a high uptake of procolipase, greatly exceeding that of Cr-51-EDTA. This was especially evident in the stomach, in which the procolipase uptak e was nonsaturable within the experimental period. Also, in the centra l nervous system (CNS), there was evidence of specific, possibly carri er-mediated, transport. These results suggest that procolipase may hav e specific, conceivably receptor-mediated, transport pathways across t he microvascular endothelium in the stomach, pancreas, duodenum, ileum , and the CNS.