Manipulating the intracellular environment of hippocampal slices: pH and high-energy phosphates

Blood flow and high-energy phosphate (HEP) content were determined simultaneously in multiple microregions of left ventricular subendocardium in 29 normal anesthetized open-chest rabbits by use of a new micromethod to determine whether a direct linear relationship existed between these parameters. Tissue samples weighed 1-2 mg. ATP and creatine phosphate (CP) content were quantitated in quick-frozen hearts by fluorometry at sites where tissue perfusion was measured by H2 clearance by use of bare-tipped platinum electrodes. A series of validation studies were conducted to ensure that 1) no significant damage to the tissue surrounding the electrode occurred during the period of experimentation and 2) no significant loss of biochemical constituents had occurred due to labile processes during freezing or storage of the tissue. Blood flow, ATP, and CP values averaged 79.1 +/- 24.1 (SD) ml.min-1.100 g-1, 4.9 +/- 1.3 mumol/g tissue, and 8.0 +/- 3.0 mumol/g tissue, respectively, and are similar to those reported in studies using larger tissue samples. Correlation between the heterogeneous distribution of tissue perfusion and HEP revealed no direct linear relationship between these parameters in the normal unstressed rabbit subendocardium.

Download Full-text

Reduced substrate oxidation in postischemic myocardium: 13C and 31P NMR analyses

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.258.5.h1357 ◽

1990 ◽

Vol 258 (5) ◽

pp. H1357-H1365 ◽

Cited By ~ 7

Author(s):

E. D. Lewandowski ◽

D. L. Johnston

Keyword(s):

Steady State ◽

31P Nmr ◽

Tca Cycle ◽

High Energy ◽

Substrate Oxidation ◽

High Energy Phosphates ◽

Atp Content ◽

And Control ◽

13C And 31P Nmr ◽

Postischemic Myocardium

13C and 31P nuclear magnetic resonance (NMR) spectra were used to assess substrate oxidation and high-energy phosphates in postischemic (PI) isolated rabbit hearts. Phosphocreatine (PCr) increased in nonischemic controls on switching from glucose perfusion to either 2.5 mM [3-13C]pyruvate (120%, n = 7) or [2-13C]acetate (114%, n = 8, P less than 0.05). ATP content, oxygen consumption (MVO2), and hemodynamics (dP/dt) were not affected by substrate availability in control or PI hearts. dP/dt was 40-60% lower in PI hearts during reperfusion after 10 min ischemia. Hearts reperfused with either pyruvate (n = 11) or acetate (n = 8) regained preischemic PCr levels within 45 s. Steady-state ATP levels were 55-70% of preischemia with pyruvate and 52-60% with acetate. Percent maximum [4-13C]glutamate signal showed reduced conversion of pyruvate to glutamate via the tricarboxylic acid (TCA) cycle at 4-min reperfusion (PI = 24 +/- 4%, means +/- SE; Control = 48 +/- 4%). The increase in 13C signal from the C-4 position of glutamate was similar to control hearts within 10.5 min. The increase in [4-13C]glutamate signal from acetate was not different between PI and control hearts. The ratio of [2-13C]Glu:[4-13C]Glu, reflecting TCA cycle activity, was reduced in PI hearts with acetate for at least 10 min (Control = 0.76 +/- 0.03; PI = 0.51 +/- 0.09) until steady state was reached. Despite rapid recovery of oxidative phosphorylation, contractility remained impaired and substrate oxidation was significantly slowed in postischemic hearts.

Download Full-text

Responses of beta-adrenoceptor in rat soleus to phosphorus compound levels and/or unloading

AJP Cell Physiology ◽

10.1152/ajpcell.1994.266.5.c1257 ◽

1994 ◽

Vol 266 (5) ◽

pp. C1257-C1262 ◽

Cited By ~ 15

Author(s):

Y. Ohira ◽

K. Saito ◽

T. Wakatsuki ◽

W. Yasui ◽

T. Suetsugu ◽

...

Keyword(s):

Contractile Activity ◽

Creatine Supplementation ◽

High Energy ◽

Hindlimb Suspension ◽

Phosphorus Compounds ◽

High Energy Phosphates ◽

High Energy Phosphate ◽

Gravitational Unloading ◽

Beta Adrenoceptor ◽

Muscle Contractile

Responses of beta-adrenoceptor (beta-AR) in rat soleus to gravitational unloading and/or changes in the levels of phosphorus compounds by feeding either creatine or its analogue beta-guanidinopropionic acid (beta-GPA) were studied. A decrease in the density of beta-AR (about -35%) was induced by 10 days of hindlimb suspension, but the affinity of the receptor was unaffected. Suspension unloading tended to increase the levels of adenosine triphosphate and phosphocreatine and decrease inorganic phosphate. Even without unloading, the beta-AR density decreased after an oral creatine supplementation (about -20%), which also tended to elevate the high-energy phosphate levels in muscle. However, an elevation of beta-AR density was induced (about +36%) after chronic depletion of high-energy phosphates by feeding beta-GPA (about +125%). Data suggest that the density of beta-AR in muscle is elevated if the high-energy phosphate contents are chronically decreased and vice versa. However, it may not be directly related to the degree of muscle contractile activity.

Download Full-text

Magnetic resonance spectroscopy of high-energy phosphates and lactate immediately after coronary artery bypass surgery

Perfusion ◽

10.1177/026765919801300508 ◽

1998 ◽

Vol 13 (5) ◽

pp. 328-333 ◽

Cited By ~ 4

Author(s):

D NF Harris ◽

J A Wilson ◽

S D Taylor-Robinson ◽

K M Taylor

Keyword(s):

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Cerebral Ischaemia ◽

Artery Bypass ◽

High Energy ◽

Jugular Bulb ◽

Resonance Spectroscopy ◽

High Energy Phosphates ◽

Intracellular Acidosis ◽

High Incidence

Hypothermic cardiopulmonary bypass (CPB) is associated with a high incidence of neuropsychological defects, marked cerebral swelling immediately after surgery and jugular bulb desaturation during rewarming. This suggests cerebral ischaemia may occur, but evidence is indirect. We studied four patients with 31P magnetic resonance spectroscopy (MRS) and four with 1H MRS before and immediately after coronary surgery. There was no visible lactate in 1H MR spectra. In 31P MR spectra, the ratio of phosphocreatine to adenosine triphosphate was maintained (before: 2.13 ± 0.86 vs after: 2.57 ± 1.31; mean ± 1 SD) and there was no intracellular acidosis (intracellular pH: 7.1 ± 0.04 vs 7.16 ± 0.08), while phosphocreatine/inorganic phosphate was increased immediately after the operation (2.92 ± 0.37 vs 6.39 ± 2.67, p = 0.03). This suggests rebound replacement of energy stores following recovery from temporary cerebral ischaemia during CPB: intra-operative studies would be needed to test this hypothesis further.

Download Full-text