We developed mathematical models that predict equilibrium distribution of water and electrolytes (proteins and simple ions), metabolites, and other species between plasma and erythrocyte fluids (blood) and interstitial fluid. The models use physicochemical principles of electroneutrality in a fluid compartment and osmotic equilibrium between compartments and transmembrane Donnan relationships f...

The interactions of acid–base status, waste nitrogen excretion and metabolism in the gulf toadfish Opsanus beta, a ureogenic teleost, were examined by exposing toadfish to a variety of water treatments. Our measurements show that, like other marine teleosts, toadfish rapidly regulate acid–base status by manipulating blood [HCO3]. Several treatments affected nitrogen excretion. The initial stage...