AJP - Endocrinology and Metabolism, Vol 256, Issue 4 E447-E452, Copyright © 1989 by American Physiological Society
Absorption of plasma proteins from peritoneal cavity of normal rats
E. Regoeczi, O. Zaimi, P. A. Chindemi and P. A. Charlwood
Department of Pathology, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada.
The present study was undertaken to examine whether the uptake of plasma
proteins from the peritoneal cavity is quantitative so that tracers could
be introduced that way for measuring their turnover. To this end, the
metabolic behavior of seven homologous plasma proteins, labeled with 125I,
was compared in rats after intravenous or intraperitoneal administration.
The animals were maintained under physiological conditions. Total body
radiation measurements showed that the degradation rates of albumin,
immunoglobulins A and G, alpha 1-macroglobulin, and transferrin were the
same regardless of the route of injection. This implies that these proteins
are quantitatively absorbed from the peritoneum without undergoing
modifications. The half-life of intraperitoneally injected alpha 1-acid
glycoprotein was consistently shorter by an average 9%, thus suggesting
that this protein becomes slightly altered if introduced that way. Only
one-half of intraperitoneally injected fibrinogen survived normally,
whereas the other underwent rapid degradation. The surviving molecules had
the same half-life as fibrinogen injected intravenously. The fraction of
surviving fibrinogen could be augmented by mixing the dose with serum.
Within a wide range of concentrations and quantities injected, the
degradation rate of transferrin remained the same. Analysis by
deconvolution of the plasma curves of albumin and alpha 1-macroglobulin
absorbed from the peritoneum showed that the transport process was
independent of protein size and, at least up to 35 mg, of the amount
injected. According to the same technique, intraperitoneally administered
diferric transferrin retained its iron during passage into the circulation.
