Interaction between paramagnetic metal complexes and intracellular water of single cells

Oocytes from Xenopus laevis were used as a well‐established model to investigate spatially resolved changes in relaxation time (T1) within a cell during exposure to copper complexes by means of 'H‐NMR‐microscopy. T1 relaxation of intracellular water was shortened in dependence on the complex concentration, the water content, and the water mobility in various cell compartments. A relatively constant T1 decrease was observed in the cytoplasm of the vegetal pole, irrespective of the type and concentration of the permeable complexes used. Since the lowest content of free mobile water molecules was detected at the vegetal pole, we concluded that this quantity was as important for the relaxation time decrease as that of the chelated paramagnetic ions. Experiments using 14C‐labeled inulin demonstrated that the paramagnetic metal complexes entered the oocytes without gross injury to their plasma membranes.