Effect of Commonly Used Vehicles on Gastrointestinal, Renal, and Liver Function in Rats

Introduction: Solubility is often a limiting factor when testing new compounds in animal experiments. Various solubilizing agents may be used, but each have their own pharmacological effects. We investigated the effects of selected vehicles having different chemical characteristics on gastrointestinal, renal, and liver function.

Methods: Rats were treated orally, intravenously or intraperitoneally and gastric emptying, intestinal transit, renal, and liver function were investigated.

Results: Gastrointestinal motility was influenced by hydroxyethylcellulose, hydroxypropyl-beta-cyclodextrin (HPbetaCD), HPgammaCD, DMSO, polyethylene glycol 400 (PEG 400), fat emulsion, and the corresponding emulsifier. Liver function was affected by HPbetaCD, HPgammaCD, DMSO, PEG 400, Polysorbate 80, Cremophor RH 40, and fat emulsion. An increase in liver enzymes was observed after PEG 400 and Polysorbate 80. DMSO interfered with clinical chemistry measurements in serum. Urinary function was modified by HPgammaCD, DMSO, PEG 400, and Polysorbate 80, while enhanced urine enzyme excretion was observed after HPbetaCD, HPgammaCD, DMSO, PEG 400, and Polysorbate 80.

Discussion: Most of the investigated vehicles changed gastrointestinal, renal, and/or liver parameters after application of a certain threshold dose for each assay. No "best" vehicle could be identified that may be used in each test system. Thus, vehicles must be selected not only on their chemical characteristics but also on their potential pharmacological activity in a given test system.