Concentrations and activity coefficients of Na+, K+ and Cl- in Aplysia californica enterocytes

Tissue water averaged 76% of tissue weight in epithelial sheets of Aplysia californica intestine. Extracellular water averaged 19.6% of total intestinal water. Intracellular Cl- concentrations averaged 110 mM with most of Cl- being bound or sequestered. Intracellular Na+ concentrations were 34.2 mM with approximately 30% bound or sequestered. Intracellular K+ concentrations were not bound and averaged 532 mM. Valinomycin lowered intracellular K+ concentrations dramatically.