Peritoneal fluid in the rabbit: permeability of the mesothelium to proteins, lipoproteins and acid hydrolases.

The peritoneal fluid in rabbits fed a normal and a cholesterol added diet was analysed for a wide variety of macromolecules of different size, viz albumin, alpha-, beta- and gamma-globulins, high density lipoprotein and lipoproteins of Sf0-12, Sf12-20 and Sf greater than 20 and three acid hydrolases, N-acetyl-beta-d-glucosaminidase, acid phosphatase and beta-glucuronidase. The composition of the lipoproteins and the concentrations of each substance were compared with corresponding values in plasma, hepatic lymph, thoraic duct lymph and leg lymph. The results indicate that the large lipoproteins of the thoraic duct lymph derived from the intestinal mucosa do not normally enter the peritoneal cavity probably because they do not mix with the subserous tissue fluid, that the macromolecular composition of peritoneal fluid resemble that of leg lymph, that the peritoneal mesothelium is freely permeable to these macromolecules and that the main plasma: peritoneal fluid barrier resides in the blood capillary membrane of the various subserous tissues.