DETERMINATION OF INTRACELLULAR CALCIUM IN-VIVO VIA F-19 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

Fluorine-19-nuclear magnetic resonance (F-19-NMR) spectroscopic detect ion of the NMR-active Ca2+ indicator ,2-bis(2-aminophenoxy)ethane-N,N, N',N'-tetraacetic acid (5F-BAPTA) is one method for measuring cytosoli c free Ca2+ concentration ([Ca2+](i)) and has been used previously to measure [Ca2+](i) in isolated cells and perfused organs. The aim of th e present investigation was to demonstrate the feasibility of determin ing [Ca2+](i) in vivo and in situ using F-19-NMR and 5F-BAPTA. Experim ents were performed on male Sprague-Dawley rats with a surface-coil an tenna employed for NMR interrogation. The Ca2+ indicator, 5F-BAPTA, wa s infused either intravenously (kidney, spleen) or intraventricularly (brain) as a 100 mg/ml solution of the cell-permeant acetoxymethyl est er (5F-BAPTA-AM) in dimethyl sulfoxide. Rats tolerated intravenous inf usion without evident change in mean arterial blood pressure. In all t issues examined, kidney, spleen, and brain, [Ca2+](i) was similar to 2 00 nM. To our knowledge, these results represent the first in vivo and in situ determinations of [Ca2+](i) employing F-19-NMR.