[Metabolic correction of the lipid-transport system in experimental diffuse purulent peritonitis]

The research was performed in 55 male chinchilla rabbits. For the first time the effect of metabolic preparations "citoflavin" and "neoton" of the protein-lipid spectrum of blood was studied in experimental diffuse purulent peritonitis. The development of diffuse purulent peritonitis caused negative changes in blood lipid-transport system which resulted in a decreased blood protein level and high density lipoproteins (HDL) and growth of triglycerides. In the HDL phospholipid spectrum the pathological changes are characterized by an increased lisophosphotide content and compensatory growth of the level of poliglycerophosphatides. A comparative analysis has shown that both preparations possess unidirectional action which is more pronounced in "citoflavin" than in "neoton".

[Simultaneous determination of exogenous phosphocreatine and its metabolite creatine in rabbit plasma using ion-pair reversed-phase high performance liquid chromatography]

A method for simultaneous determination of exogenous phosphocreatine (PCr) and its metabolite creatine (Cr) in rabbit plasma was developed by using an ion-pair reversed-phase high performance liquid chromatography (IP-RP-HPLC). The pharmacokinetics (PK) of PCr was also investigated. In the IP-RP-HPLC method, a Kromasil C,8 column was used with methanol and phosphate buffer containing tetrabutylammonium hydrogen sulfate (TBA, ion-pair reagent) as the mobile phases in a gradient elution mode, while changing detection wavelength and flow rate. The internal standard method was used to quantify PCr and Cr, and the baseline subtraction method was applied. The calibration curves showed good linearity ranged from 10 to 7 500 mg/L for PCr and from 10 to 1 500 mg/L for Cr, and the correlation coefficients (r) were greater than 0. 999. The methodology validation showed high specificity, precision and recovery with the intra-day and inter-day relative standard deviations (RSDs) of not more than 6. 2%, accuracies of 96. 5% - 102. 4%, and extraction recoveries of more than 92%. After intravenous injection of PCr, the concentration-time profile can be best described by two-compartment model with elimination half time of (20.4 +/- 2.7) min, apparent volume of distribution of (0.179 +/- 0.037) L/kg and clearance rate of (0.019 +/- 0. 002) L/(kg x min). The Cr appeared rapidly with time to maximal concentration of 30 min, elimination half time of (43.7 +/- 4. 5) min. The results of practical application showed that this bio-analytical method can completely meet the requirements for PK study of PCr in rabbit plasma.

[Pharmacokinetics and metabolic disposition of exogenous phosphocreatine in rats]

This article is report the study of the pharmacokinetics and metabolic disposition of exogenous phosphocreatine (PCr) in rats by means of an ion-pair HPLC-UV assay. PCr and its metabolite creatine (Cr) and related-ATP in rat plasma and red blood cell (RBC) were simultaneously determined. A blank plasma and RBC were initially run for baseline subtraction. Plasma and RBC samples were deproteinized with 6% PCA prior to HPLC. Following i.v. administration of PCr 500 mg x kg(-1) and 1 000 mg x kg(-1) the C-T curve could be described by the two-compartment model with t1/2beta 22.5-23.3 min, V(d) 0.956 4-0.978 6 L x kg(-1), CL 0.029 L. kg(-1) x min(-1). The Cr as PCr degraded product appeared as early as 2 min post i.v. dosing with t(max) 20 min, t1/2kappa (m) 40.6-42.7 min and f(m) 60%-76%. After po administration of PCr, the parent drug in plasma was undetectable, but the metabolite Cr was detected with t(max) 65-95 min, t1/2kappa (m) 56.0-57.7 min, metabolite-based bioavailability F(m) 55.02%-62.31%. PCr i.v. administration resulted in significant elevation of ATP level in RBC but not in plasma, the related-ATP in RBC was characterized by t(max) 68-83 min, t1/2kappa 49-52 min. In RBC no exogenous PCr was found but Cr was detected following i.v. administration of PCr, with the t(max) 120 min and t1/2k (m) 70 min for Cr. The above results indicate that PCr eliminates and bio-transforms in body very rapidly; K > K(m) confers ERL, instead of FRL, type upon the metabolic disposition of Cr. Following po administration of PCr, the degraded product Cr is absorbed but not the parent drug PCr. The formed Cr can be accounted for by most of i.v. and po PCr. Intravenous dosing leads apparently increased and sustained Cr and related-ATP concentration in RBC.

Effect of oral phosphocreatinine on human skeletal muscle shown by in vivo 31P-NMR

We used the non-invasive method of in vivo phosphorus magnetic resonance spectroscopy to investigate the effect of oral administration of phosphocreatinine on muscle energy metabolism during graded work and post-exercise recovery in humans. Phosphocreatinine administration results in a smaller depletion of phosphocreatine at high work rates accompanied by a smaller cytosolic acidification during work and recovery. Our findings suggest that oral phosphocreatinine increases the readily available energy for muscle contraction by interfering directly or indirectly with the reaction equilibria involving phosphocreatine.

The synthetic phosphagen cyclocreatine phosphate inhibits the growth of a broad spectrum of solid tumors

BACKGROUND

The brain isoform of creatine kinase (CKBB), an enzyme involved in energy metabolism, has been implicated in cellular transformation process. Cyclocreatine (CCr), a creatine kinase (CK) substrate analogue, was shown to inhibit the growth of a broad spectrum of solid tumors expressing high levels of CK. Cyclocreatine phosphate (CCrP) generated by CK, was proposed to be the active form responsible for growth inhibition.

MATERIALS AND METHODS

We synthesized CCrP and tested its cellular uptake and anti tumor activity in stem cell assays and in athymic mouse models.

RESULTS

CCrP seems to be taken up by cells and inhibits the growth of solid tumors with high levels of CK. CCr and CCrP have similar specificity and potency.

CONCLUSION

The observation that only high-CK cell lines were responsive to CCrP, similar to CCr, indicates that the enzyme requirement was not bypassed. We propose that CK is a target for CCrP, and is involved in mediating its antiproliferative activity.

Measurement of pharmacodynamic effects of dexamethasone on epidermis by phosphorus nuclear magnetic resonance spectroscopy in vitro

An intact, viable epidermal preparation was perfused and phosphoenergetic and phospholipid metabolite levels were measured by 31P NMR. The preparation was stable in the NMR perfusion apparatus for 24 h. The effects of inclusion of ethanolamine and dexamethasone-21-acetate in the perfusion media on phosphorus-containing metabolites was assessed by examination of serial 31P NMR spectra. Phosphomonoesters increased significantly during the fourth hour of perfusion with ethanolamine (3 mM) and remained elevated. A corresponding decrease in nucleotide triphosphates was noted, but phosphocreatine (PCr) remained unchanged. Dexamethasone perfusion resulted in a biphasic effect on phosphomonoester metabolism and a dose-dependent decrease in PCr and nucleotide triphosphate levels. A log-linear relationship was observed between dexamethasone dose in the 1-100-nM range and a decrease in PCr. These techniques with an isolated intact epidermal preparation are useful for elucidating mechanisms of corticosteroid action on the skin and serve as a basis for developing a mechanistically relevant topical corticosteroid bioequivalence technique.

Brain maturation and high-energy phosphate diffusivity: alteration in cytosolic microenvironment and effective viscosity

Maturational changes in intracellular brain phosphocreatine (PCr) transport were investigated using 31P-nuclear magnetic resonance diffusion spectroscopy. The diffusivities of PCr showed significant maturational facilitation in rat brain in vivo. Physicochemical analysis of the cytosol microenvironment as a multicomponent solution, where one of the components is a dilute polymer, indicated that the observed developmental facilitation of PCr diffusivity is likely to be due to a decline in the concentration of the free amino acid taurine. Changes in the concentrations of biopolymers (i.e., proteins or lipids) have only little effect, if any, on PCr diffusivity. PCr diffusivity values of rat brain measured in vivo showed excellent quantitative agreement with the predicted values estimated using a model for multicomponent diffusion. The study confirmed that the taurine/N-acetylaspartate exchange observed during postnatal development of rat brain plays a major, it not unique, role in maturational facilitation of intracellular high-energy phosphate transport.

Cyclocreatine (1-carboxymethyl-2-iminoimidazolidine) inhibits growth of a broad spectrum of cancer cells derived from solid tumors

In an effort to investigate the role of creatine kinase and its substrates in malignancy we have tested the effect of cyclocreatine [1-carboxymethyl-2-iminoimidazolidine (CCr)] on the growth of tumor cells in vitro and in vivo. CCr is phosphorylated by creatine kinase to yield a synthetic phosphagen [(N-phosphorylcyclocreatine (CCr approximately P)] with thermodynamic and kinetic properties distinct from those of creatine phosphate. We show that CCr accumulates as CCr approximately P in tumor cells expressing a high level of creatine kinase, and that the accumulation of this phosphagen is detrimental to tumor cell growth. Tumor cell lines expressing a low level of creatine kinase accumulate much less CCr approximately P, and consequently are growth inhibited only at higher concentrations of CCr. When these resistant cells are transfected with a creatine kinase B expression vector, they express creatine kinase, accumulate CCr approximately P, and are growth inhibited. In vivo, in nude mouse xenografts, the rate of growth of a high creatine kinase expressing tumor cell line is inhibited in animals fed 1% CCr. Our results indicate that CCr inhibits the growth of tumor cells in vitro and in vivo.

In vivo assessment of mitochondrial functionality in human gastrocnemius muscle by 31P MRS. The role of pH in the evaluation of phosphocreatine and inorganic phosphate recoveries from exercise

In this study we compared the kinetics of phosphocreatine (PCr) and P(i) recovery, and their dependency on cytosolic pH in 38 normal individuals. Spectra were acquired during rest, work and recovery. A time resolution of 10 s was used to obtain detailed information. The kinetics of PCr and P(i) recovery almost overlapped when the lowest value of cytosolic pH reached during recovery (termed the minimum pH) was < 6.95, while they were completely dissociated when the minimum pH was > 6.95. This result is interpreted as indirect in vivo evidence of the kinetic control exerted by ADP on mitochondrial oxidation. Our results represent a rationale for new experimental conditions to be used in clinical routine studies of pathologies due to primary or secondary mitochondrial malfunction.

Early developmental exposure to benzodiazepine ligands alters brain 31P-NMR spectra in young adult rats

Alterations in brain high energy phosphate compounds, using 31P-NMR (nuclear magnetic resonance) spectroscopy, were measured in vivo in young adult (3-4 months) rats following prenatal exposure to ligands acting specifically at benzodiazepine (BDZ) binding sites. The exposure induced a decrease in intracellular pH that indicated a predominant interaction of the drugs in utero with central-type BDZ receptor sites. Late gestational exposure to BDZ ligands also induced changes in brain phosphocreatine (PCr) utilization. Exposure to the lowest dose of DZ (1.0 mg/kg) but not the higher dose (2.5 mg/kg) induced a significant change in PCr utilization. Exposure to the central-type BDZ receptor antagonist RO15-1788 alone clearly altered PCr utilization in adult offspring, and DZ (2.5 mg/kg) when administered concurrently was not able to prevent this effect. Though exposure to a peripheral-type ligand (PK11195) had no effect by itself, it converted the effect of the high dose of DZ to that of the low dose. Together, these results indicate an interaction during development between the central and peripheral-type BDZ binding sites on organization and/or regulation of cellular energy metabolism. Normalized ATP levels were not changed by any prenatal treatment indicating adequate buffering of intracellular ATP by phosphocreatine. The dopaminergic antagonist haloperidol did not alter intracellular pH or any index of phosphate metabolism indicating a selective receptor mediated role for BDZ ligands in influences on the long term organization of intracellular phosphate metabolism.