Influence of shaking on peritoneal transfer in rats

To determine the role played by stagnant peritoneal fluid layers in the diffusion of solutes between peritoneal cavity and blood, we measured peritoneal transfer of urea, creatinine [¹⁴C]-L-glucose and protein in anesthetized rats shaken at varying rates on an orbital platform shaker. The diffusion transfer rates of the low molecular weight solutes increased dramatically with shaking, with near maximal values obtained at a shaking rate of 250 RPM. The permeability · area product (PA) for each of the low molecular weight solutes increased about fourfold with rapid shaking while the PA of protein increased by only about 50%. It seems likely that shaking increased PA primarily via reduction of the thickness of stagnant peritoneal fluid layers, although increases in surface area or changes in tissue permeability cannot be excluded certainty. We conclude that stagnant fluid layers probably are the rate limiting step in diffusive peritoneal transfer of low molecular weight solutes in stationary rats.