THE MULTIXENOBIOTIC RESISTANCE MECHANISM IN THE MARINE SPONGE SUBERITES DOMUNCULA - ITS POTENTIAL APPLICABILITY FOR THE EVALUATION OF ENVIRONMENTAL-POLLUTION BY TOXIC COMPOUNDS

Experiments were carried out with the marine sponge Suberites domuncal a to determine whether sponges may express - like mammalian tumor cell s a multidrug-like transporter system. The results demonstrate that sp onge cells possess such a protective system termed multixenobiotic res istance (MXR) pump or P-glycoprotein-like pump, The protein was identi fied by antisera for the mammalian P170 multidrug resistance protein a s a 130 kDa molecule, Binding studies were performed with H-3-vincrist ine (H-3-VCR) and membrane vesicles; this process is ATP-dependent and inhibited by verapamil, which is known to reverse the multidrug-resis tance phenotype in mammalian systems, Accumulation experiments were pe rformed to demonstrate that the uptake of H-3-VCR is time-dependent, a nd increases at elevated extracellular levels of H-3-VCR, Application of the dyeing technique with calcein-AM, a suitable functional assay f or multidrug transporter systems in mammal cells, also revealed the ex istence of the MXR pump in S. domuncula plasma membranes. These data d emonstrate that S. domuncula is provided with a multidrug-like transpo rter, the MXR pump, which might function as a protection system for sp onges in polluted environments.