Permeability of peritoneal membrane "in vitro" under the effect of methotrexate

Bi-directional transport of urea (U), uric acid (UA), inulin (I) and albumin (A) across rabbit peritoneum and its change under the influence of methotrexate (MTX) was studied in vitro. The transport coefficients increased with decreasing molecular mass of these compounds. MTX diminished the bi-directional transfer of U and UA by about 35% but no changes in I transport were found. Flux of A directed from the mesothelial to the interstitial side of the membrane under the influence of MTX was increased by about 35%, while the transport in the opposite direction remained unchanged. The obtained results confirm previous hypothesis concerning the membrane point of MTX. Suggestion of a complex mode of this action within peritoneal membrane was put forward.