th  - 1988 - 51st ENC Conference

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GLUCOSE METABOLISM IN PERFUSED HEARTS MONITORED BY
I13C NMR SPECTROSCOPY: A MORE SENSITIVE INDICATOR OF
ALTERED FLOW THAN HIGH ENERGY PHOSPHATE LEVELS.
V. P. Chacko*, R. G. Weiss, J. D. Glickson and G. Gerstenblith
The Johns Hopkins Medical Institutions, 600 N. Wolfe St., Baltimore, MD 21205
Cardiac metabolism was studied in the intact, beating, perfused rat heart using
13C NMR Spectroscopy and correlated with function and 31p NMR assessment of high
energy phosphates, inorganic phosphate, and cellular pH during normal (15 ml/min)
and graded reductions (5 ml/min & 2 ml/min) in coronary flow. Despite a 50% mean
reduction in developed pressure at 5 ml/min flow, there was no change in levels of
PCr, ATP, Pi or pH throughout the 60 minute period. There were, however, marked
metabolic changes detected by 13C NMR monitoring levels of glutamate and lactate.
These changes were not due to decreased delivery of glucose during low flow, as
matched reductions in delivery achieved by lowering perfusate glucose during normal
flow did not reproduce the low flow profile. The results are consistent with an
increased dependence on anaerobic metabolism, and a reduction in tricarboxylic acid
cycle flux during low flow. A delayed time to half maximum enrichment of the C2
glutamate peak, but not the increased lactate levels, could be produced by
decreasing workload to match that present during low flow by decreasing perfusate
calcium concentration, indicating a close relationship between workload and this 13C
NMR index of TCA flux. Further reduction in flow to 2 ml/minute resulted in further
delay in the time to half maximum enrichment of C2 glutamate isotopomer, higher
livels of lactate, as well as the classical "ischemic" changes in the 31p NMR
spectra. Thus, 13C NMR spectroscopy can be used to characterize metabolic changes
during reduced flow and altered workloads and is more sensitive than 31p NMR
spectroscopy in identifying hypofunctional myocardium in which modest flow (supply)
reductions are accompanied by a balanced down-regulated workload (demand).
6~ ] Cu NQR OF YBa2CusO x WITH VARYING OXYGEN CONTENT:
A. J. Vega*, W. E. Farneth, R. K. Bordia, and E. M. McCarron, Central
Research and Development Department, E. I. du Pont de Nemours and
Company, Experimental Station, Wilmington, Delaware 19898.
The 63Cu and 6SCu NQR spectra of YBasCusO x show a strong dependence
on the oxygen content when x is varied from 6 to 7. For x=7 two
signals are observed at room temperature. The room-temperature
signals generally consist of a short-T 1 (< 1 ms) and a long-T 1
component (~ 100 ms). The relative intensity of the short-T I
component gradually decreases from 100% to 0% when x is decreased
from 7.0 to 6.0. In addition, the line shapes of the two T 1
components are strongly dependent on the oxygen content. While the
short Tl'S are attributed to a Korringa-type relaxation mechanism
involving the conduction electrons, it may be assumed that the Cu
sites with the longer T 1 values are not directly associated with the
conduction process. The NQR data can thus be used to help interpret
the strong dependence of T c on the oxygen content of these
superconducting materials.
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