NMR STUDIES OF METAL IONS IN INTACT CELLS AND TISSUES

细胞内金属离子调节多种细胞和组织

Intracellular metal ions modulate a variety of cellular and tissue functions. A long range goal of our research is to understand possible regulatory roles of these ions in cellular proliferation, differentiation, volume regulation, and hormonal control of various cellular processes. We seek also to understand how the concentrations of intracellular ions are managed by various membrane transport processes, and how such regulation goes astray in disorders such as cancer, hypertension, diabetes, and sickle cell disease. Our primary research tool is NMR spectroscopy. We have recently developed new NMR approaches for measuring free Mg++ (by analyzing 31P NMR of intracellular ATP) and Na+ ions (using an anionic paramagnetic reagent Dy(PPPi)2 introduced by us to distinguish between intra- and extracellular Na+ ions). The choice of cells and tissues for our research includes human normal and sickle erythrocytes, peripheral blood lymphocytes, isolated rat cardiac myocytes, amphibian eggs, and rat tail artery. Specific aims to be pursued are: (1) To determine if bound Na+ exists, and is functionally significant, by quantitating NMR-visible and total intracellular Na+ ion concentrations in various types of cells and physiological states; (2) If indeed a sizable part of intracellular Na+ in human erythrocytes is NMR-invisible as indicated by our preliminary experiments, to determine if it is sequestered in the cell membrane and cytoskeleton, and whether it can be released by intracellular Ca++ ions; (3) To study localization of Na+ ions in various intracellular compartments in amphibian oocytes; (5) To find out if partially relaxed 23Na FT NMR spectra can be used to detect the existence of compartments with differing relaxation behaviour and magnetic environments within an intact cell; (5) To follow changes in [Nai], pHi, [Mgi2+] during mitotic cell division cycles in synchronously dividing amphibian oocytes; (6) To ascertain if an abnormality in the regulation of intracellular Na+ ions is associated with the disordered mitotic rate and maturation sequence of leukemic lymphocytes; (7) To characterize the state of Na+ and K+ ions in normal and sickle red blood cells in oxygenated and deoxygenated states; (8) To investigate the effects of insulin upon membrane systems involved in the transport of Na+, K+ and H+ ions in amphibian oocytes and mammalian cardiac myocytes and to determine whether such effects are mediated by proteolytically generated peptides; and (9) To test the hypothesis that an increased NMR-visible intracellular Na+ is associated with essential hypertension.