Creatine and Cyclocreatine Effects on Ischemic Myocardium: ³¹P Nuclear Magnetic Resonance Evaluation of Intact Heart

Abstract

The purpose of this study was to investigate the effects of prior dietary supplementation with creatine (Cr) or cyclocreatine (Cy, a synthetic analogue of Cr) on high energy phosphate metabolism of the ischemic myocardium. To this end, 48 rats were fed the following powdered rat chow diet for 21 days: 16 were fed chow without additives (CON); 16 were fed a diet containing 1 % Cr by weight (CR); 16 were fed a diet containing 1 % Cy by weight (CY). At the end of the feeding period, rats were anesthetized, hearts harvested and perfused in the Langendorff mode using Krebs-Henseleit buffer (maintained at 37 °C, equilibrated with 95% 02/5% CO2) to which 11 mM glucose was added. ³¹P nuclear magnetic resonance (NMR) studies of myocardial bioenergetics were done using a Bruker AM 500 spectrometer. After acquisition of preischemic spectra, global ischemia was produced by clamping aortic inflow. Ischemia was maintained until adenosine triphosphate (ATP) became NMR invisible (CON =34 ± llmin;CR = 32 ± 13min;CY = 56 ± 13min;p < 0.05 CY vs. CR and CON). Half-lives of ATP were 19 min for CON and CR and 37.5 min for CY; half-lives of phosphagen were 4 min for CON and CR and 11 min for CY. Time for return of mechanical function (heart rate × systolic pressure) after ischemia was similar for all three groups (CON = 28 ± 28, CR = 34 ± 22, and CY = 22 ± 15 min), even though the CY group was subjected to longer periods of ischemia). These data indicate that CY, but not CR, pretreatment provides myocardial protection either during and/or after ischemia and allows return of mechanical function after much longer episodes of ischemia than in CON and CR. One factor in the mechanism of protection may be the prolonged maintenance of phosphagen due to the higher equilibrium concentration of phosphocyclo-creatine which in turn provides substrate for continued synthesis of ATP during and after ischemia, thus defining Cy as a bioenergetic protective agent. Other mechanisms of protection remain to be defined.

Attenuation by creatine of myocardial metabolic stress in Brattleboro rats caused by chronic inhibition of nitric oxide synthase

“…However, uptake was greater than in previous studies, where creatine was added to rat chow (Osbakken et al, 1992), and was still sufficient to counter the adverse metabolic effects of L-NAME in the present work. The reduction in total creatine following L-NAME administration (Figure 1) was unexpected, but suggests that L-NAME could have influenced creatine biosynthesis and/or myocardial creatine uptake and release.…”

Mitochondrial Pathways, Permeability Transition Pore, and Redox Signaling in Cardioprotection: Therapeutic Implications

“…Nevertheless, several biochemical and metabolic alterations have been observed in the hypertrophic myocardium. These include altered mitochondrial energetics and ATP production and alterations in glycolytic metabolism with lactate accumulation during ischemia (4,250,257). Moreover, increased ROS generation and reduced antioxidant potential have been described (13).…”

Noninvasive measurement of gene expression in skeletal muscle

“…In vivo basal 31 P spectra from the hindlimbs of a 6-mo-old mouse. 31 P-MRS spectra from the rAdCMVAK-injected limb (Upper spectrum) reveal a 31 P resonance at the chemical shift for PArg that is not present in the contralateral control limb (Lower spectrum). AK as a Noninvasive Marker Gene.…”

“…Magnetic field homogeneity was adjusted using the free proton signal, resulting in a typical full width half maximum of 0.2 parts per million (ppm). 31 P-MRS spectra were obtained with a pulse repetition time of 5.4 s, a pulse width of 20 micro seconds, a spectral width of 12,000 Hz, and 4,096 complex data points. Peak areas, chemical shifts, and line widths were measured by using time domain analysis.…”

“…A recombinant adenovirus was constructed by using the gene for arginine kinase (AK), which is the invertebrate correlate to the vertebrate ATP-buffering enzyme, creatine kinase. Gene expression was noninvasively monitored using 31 P-magnetic resonance spectroscopy ( 31 P-MRS). The product of the AK enzyme, phosphoarginine (PArg), served as an MRS-visible reporter of AK expression.…”