Hydraulic conductivity, albumin reflection and diffusion coefficients of pig mediastinal pleura

Hydraulic conductivity (L), albumin reflection coefficient (sigma), and albumin diffusion coefficient (D) were measured across pig mediastinal pleura. The tissue (7 mm diameter) was bonded between two chambers. Flow (Q) of lactated Ringer solution between the chambers was measured in turn at driving pressures (Delta P) of 2, 4, and 6 cm H2O. Value of L was proportional to the slope of the Q-Delta P curve. Then Q was measured in turn at three albumin osmotic pressure differences (Delta pi r equivalent to -1, -2, and -3 g/dl albumin concentration difference, Delta C) with Delta P constant at either 2, 3, 4, or 6 cm H2O. From Starling's equation, magnitude of a was the slope of the Q-Delta pi curve divided by the slope of the Q-Delta P curve. We measured the diffusion of 0, 2, 5, and 10 g/dl albumin with tracer I-125-albumin. Tracer mass (M) that diffused across the pleura was measured for 10 h using a well-type NaI(T1) detector. D was calculated from the slope of the M-time curve. Values of L averaged 2.0 x 10(-8) cm(3).s(-1).dyne(-1) (n = 23). Values of sigma were small (0.02-0.05) and sigma increased as now increased 20-fold. D (n = 24) increased 3-fold from 2.7 x 10(-8) cm(2)/s as Delta C increased from 0 to 10 g/dl. The small values of sigma indicated that mediastinal pleura provided little restriction to the passage of protein. (C) 1999 Academic Press.