Similitude of transperitoneal permeability in different rodent species

Transgenic mice facilitate mechanistic studies of altered peritoneal transport, but the majority of transport studies have been carried out in rats. We hypothesized that mouse transport parameters, normalized to the peritoneal contact area, would be similar to those of the rat. To address this, we affixed small ( approximately 10-mm diameter) plastic chambers to the serosa of the abdominal wall of anesthetized CD1 and C57BL mice. The chamber constrained transfer across the area of the chamber base and facilitated mixing, volumetric, and concentration measurements vs. time for mannitol, serum albumin, and osmotic and hydrostatic pressure-driven convection. The mass transfer coefficient of mannitol (MTC(M)) and of serum albumin (MTC(BSA)), hydrostatic pressure-driven flux (J(P)), and osmotic filtration (J(osm)) were calculated from the time-dependent volume and concentration data. The units of all parameters (microl x min(-1) x cm(-2)) were compared with previously derived parameters from SD rats with a one-way ANOVA. Results indicated small but significant differences in MTC(BSA) (x10(2)): CD1, 9.72 +/- 1.97, n = 6; C57BL, 7.13 +/- 1.52, n = 10; rat, 12.5 +/- 1.6, n = 17 (P = 0.03). ANOVAs of all other parameters were not significant and confirmed our hypothesis: MTC(M) (CD1, 3.20 +/- 0.38, n = 7; C57BL, 2.34 +/- 0.41, n = 6; rat, 2.72 +/- 0.23 n = 19), J(P) (CD1, 0.77 +/- 0.15, n = 10; C57BL, 0.33 +/- 0.13, n = 15; rat, 0.51 +/- 0.16, n = 9), or J(osm) (CD1, 0.92 +/- 0.35, n = 6; C57BL, 0.49 +/- 0.35, n = 6; rat 1.72 +/- 0.35, n = 6). We conclude that elimination of the variable peritoneal transfer area normalizes calculated transport characteristics and facilitates comparison between species.