Hydraulically-induced convective solute transport across the rabbit peritoneum

Area of Science:

• Physiology
• Renal Physiology
• Transport Phenomena

Background:

• Solute transport during transperitoneal ultrafiltration is lower than predicted by diffusion alone.
• The heteroporosity hypothesis suggests osmotic convective transport occurs in small arteriolar pores and diffusion in large venular pores.

Purpose of the Study:

• To test the heteroporosity hypothesis by examining solute transport during hydraulically-induced ultrafiltration.
• To determine if convective and diffusive transport utilize the same peritoneal capillary pores.

Main Methods:

• Eviscerated New Zealand White rabbits (N=13) underwent hydraulically-induced transperitoneal ultrafiltration.
• Sieving coefficients (S) were measured for creatinine, p-aminohippurate (PAH), and neutral dextran.
• Control experiments (N=6) assessed the impact of evisceration on peritoneal transport characteristics.

Main Results:

• Sieving coefficients for creatinine (0.72 ± 0.03) and PAH (0.67 ± 0.05) were lower than unity and similar to values from osmotic ultrafiltration.
• Dextran sieving coefficients ranged from 0.50 (13 Å) to 0.40 (50 Å), higher than previously observed but still below unity.
• Control experiments indicated evisceration affected surface area but not transport characteristics.

Conclusions:

• The heteroporosity hypothesis does not fully account for the observed diffusive and convective solute transport properties of the peritoneum.
• Hydraulically-induced ultrafiltration provides a model to study convective solute transport through peritoneal capillaries.
• Peritoneal solute transport involves mechanisms beyond the simple pore model proposed by the heteroporosity hypothesis.