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PubMed1992

Mouse peritoneal macrophages contain an acylating system specific for twenty-carbon polyunsaturated fatty acids. A study with intact cells.

It is widely recognized that in addition to regulating the expression and activity of arachidonic acid (AA)-metabolizing enzymes, the availability of free AA limits eicosanoid biosynthesis. AA participates in a deacylation/reacylation cycle of membrane phospholipids in which the fatty acid is cleaved by phospholipase A2 and reesterified by acyltransferase. Thus, free AA can become available either by phospholipase A2 activation or by inhibition of fatty acid reincorporation. We observed that exposure of [3H]AA-prelabeled macrophages to micromolar concentrations of unlabeled AA resulted in a net release of 3H-radioactivity into the extracellular medium. This was not the consequence of phospholipase A2 activation, but of impaired reesterification of previously liberated [3H]AA. The eicosanoid precursors eicosatrienoic acid (ETA) and eicosapentaenoic acid (EPA) mimicked the effect of unlabeled AA on 3H-radioactivity release from [3H]AA-prelabeled macrophages, but all other fatty acids tested were ineffective. Similarly, only AA, ETA and EPA were able to inhibit [3H]AA uptake by macrophages, all other fatty acids being ineffective. From these data, it is concluded that intact macrophages contain an acylating system specific for the eicosanoid precursors AA, ETA and EPA. Altogether, the results of this study underscore the importance of fatty acid reacylation in controlling free AA levels in macrophages.

8,11,14-Eicosatrienoic Acid↗
PubMed1991

Penetration of lysophosphatidylcholine into the dermis.

The ability of Lysophosphatidylcholine (LPC) to penetrate into the dermis and its degradation were investigated in vivo using hairless rats. Phosphatidylcholine (PC) was used as a control. Radioactively labelled LPC and PC were applied on the surface of skin, and the radioactivities of the epidermis and dermis were measured at 8, 24, and 48 hours. The recoveries of radioactive materials of LPC and PC within the area of epidermis and dermis at 8 hours were 0.21% and 0.25%; at 24 hours, 0.68% and 0.31%; and at 48 hours, 0.42% and 0.92%. No radioactivity was detected in serum. The radioactive substances which had penetrated were identified as LPC, PC, diglycerides, and free fatty acids. It was also found that topical application of LPC did not change the structure of skin as seen by microscopical examination. These findings indicate that a small amount of LPC can penetrate without the damaging skin structure and is enzymatically degraded into several lipids. Since LPC has bactericidal and antiviral activity, this substance could be an useful agent for dermatological use.

Animals↗
PubMed1991

The catabolism of exogenous lysophosphatidylcholine in isolated perfused rat and guinea pig hearts: a comparative study.

Lysophosphatidylcholine (lysoPC) is an arrhythmogenic phospholipid metabolite which accumulates in the ischemic myocardium. Reduced catabolism of lysoPC has been proposed to be one of the biochemical mechanisms responsible for the increase in lysoPC content. In this investigation we compared the microsomal catabolism of exogenous labeled lysoPC in isolated perfused rat and guinea pig hearts. Analysis of the amount of radioactivity in microsomal phosphatidylcholine (PC) and free fatty acid (FFA) was used as an index of the participation in lysoPC clearance by acylation catalyzed by acyl-CoA:lysoPC acyltransferase and deacylation catalyzed by lysophospholipase, respectively. There was no significant difference in the incorporation of radioactivity into rat and guinea pig heart microsomes; however, the patterns of radioactivity in lysoPC metabolites were notably different. Equal participation by deacylation and reacylation was observed in rat microsomes, whereas deacylation was clearly the preferred route for lysoPC clearance in guinea pig microsomes. Modulation of enzyme activity by treatment of the isolated heart with pHMB, a sulfhydryl agent, was used to probe the relationship among acylation, deacylation and the extent of lysoPC clearance. In guinea pig microsomes impairment of lysoPC acylation was not associated with any change in the amount of radioactivity in lysoPC because of a compensatory increase in deacylation. In contrast, impaired deacylation in rat microsomes led to significant elevations in the amount of radioactivity in lysoPC. We conclude, therefore, that in intact perfused rat and guinea pig hearts the relative participation of acylation and deacylation in lysoPC clearance differs. Moreover, we propose that the level of deacylation by lysophospholipase is an important factor in the extent of clearance of lysoPC.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1984

Use of oily contrast medium for selective drug targeting to tumor: enhanced therapeutic effect and X-ray image.

Highly malignant rabbit tumor (VX-2) was implanted at the periphery of the liver in 63 rabbits. Selective delivery of the anticancer agent copoly(styrenemaleic acid) conjugated to neocarzinostatin (SMANCS), which was dissolved in an oil contrast medium (Lipiodol), was performed by injection via the proper hepatic artery. The anticancer effect was also evaluated by various parameters. By using low-kVp X-ray examination of the resected rabbit liver, Lipiodol was found to distribute throughout the entire liver arterial lumina and was retained there for about 24 hr, but disappeared from the normal liver arterial lumina gradually. However, Lipiodol was retained in the tumor tissue and vessels for at least 7 days, whereas it was undetectable in any other organs. A radioactive analogue of Lipiodol, a chloroiodinated fatty acid, was prepared by using [14C]linoleic acid. This analogue was used in the study of the distribution by low-kVp X-ray examination, Sudan III staining, and autoradiography. Lipiodol remained in the tumor vessels as well as the tumor cells. The use of the radioisotope yielded a quantitative profile of Lipiodol accumulation in tumor tissues; approximately 1000 times more at 15 min and 100 times more at 3 days after the injection than that of most other organs or plasma. Its major excretion route appeared to be through the bile and then the feces. The biological activity of SMANCS was also determined and was found to be significant in both tumor and liver even 7 days after injection. No activity was found in any other organ or tissue. The relatively high biological activity of SMANCS in the nontumorous liver adjacent to the tumor may be the result of continuous drug release from SMANCS-Lipiodol in the tumor tissue. By histological examination, massive tumor necrosis and infiltration of the inflammatory cells were found in the rabbits treated with SMANCS-Lipiodol. In the rabbits treated with Lipiodol alone, necrosis of the tumor was only minimal, and no infiltration of inflammatory cells was observed. Survival periods of the treated rabbits (n = 14) were significantly longer than those of controls (n = 10); 23.1 +/- 5.5 (S.D.) days versus 16.1 +/- 2.9 days (p less than 0.005), respectively, even though only one injection was used for this highly malignant tumor. Mean tumor size for both groups at laparotomy was 163.3 +/- 83.0 sq mm and 160.5 +/- 76.5 sq mm, respectively (not significant).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1981

Incorporation of [3H]acetate into L-cell lipids. Dependence on method of linoleate administration and timing of the pulse label.

An aqueous solution containing 5 mumol of sodium linoleate was supplied to cultures of L-fibroblasts by two methods: (a) direct addition to the culture as a single dose at the start of a 48 h incubation period (method I); or (b) infusion into the culture at a constant rate throughout the same time period (method II). At 23 h and 47 h the cells were subjected to a 1 h pulse of [3H]acetate. At 23 h method I was 1.2-times as effective as method II in reducing incorporation of radioactive label into cell sterol. Conversely, the decrease in utilization of [3H]acetate for acyl group biosynthesis was 1.7-times greater by method II than by method I. At 47 h both methods had similarly reduced [3H]acetate incorporation into both fractions by 85%. Regardless of the method used for supplementation, the large decline in biosynthesis from [3H]acetate noted at 47 h was not accompanied by any corresponding decrease in the total amount of sterol synthesized. Additional data suggest that 50% of more of the decrease in [3H]acetate incorporation at this time may be attributable to metabolites derived from the unlabeled exogenous fatty acid, which act to dilute the radioactively labeled tracer and/or to inhibit endogenous lipid biosynthesis.

Acetates↗
PubMed1972

Stages of uptake and incorporation of micellar palmitic acid by hamster proximal intestinal mucosa.

The stages of uptake and incorporation of micellar palmitic acid by hamster proximal intestinal mucosa were investigated by incubation of everted sacs at 4 degrees C and 37 degrees C for 2, 5, 10, and 15 min in a micellar solution (10 micro moles of [1-(14)C]palmitic acid, 10 micro moles of monoolein, and 100 micro moles of sodium taurodeoxycholate) and subsequent serial rinsing of the sacs in ice-cold solutions as follows: one 20-sec rinse in unlabeled micellar solution, five 1-min rinses in Krebs-Ringer buffer (0.15 m, pH 6.3), and ten 2-min rinses in 2.5% albumin solution. The fatty acid-solubilizing capacity of all the rinsing solutions was always in excess of the amounts of radioactive palmitic acid released during each rinse. Radioactivity was determined in the tissue homogenates, rinsing solutions, and serosal fluids. The results indicate that a significant proportion of radioactive palmitic acid taken up by the sacs during the short incubation was released into the rinsing solutions. Rinsing in Krebs-Ringer buffer resulted in release of 15.5 +/- 2.4% of the labeled fatty acid, and this fraction was independent of the temperature of incubation. In contrast, the amounts of palmitic acid released in albumin were significantly greater and were markedly dependent on the temperature of incubation; a total of 48.6 +/- 7.0% and 26.3 +/- 5.1% was released from sacs incubated at 4 degrees C and 37 degrees C, respectively. While the proportion of radioactive palmitic acid in the free fatty acid fraction of the tissue after the rinsing sequence remained reasonably constant regardless of the temperature and duration of incubation, the radioactivity of the esterified palmitic acid in the tissue was much greater in the sacs incubated at 37 degrees C and tended to increase linearly up to 10 min of incubation. A highly significant inverse relationship was found between the fraction of radioactive palmitic acid released by rinsing in albumin and the fraction of the label in the tissue esterified fatty acids. The results suggest that the initial uptake of micellar fatty acid by intestinal mucosa may involve reversible binding to superficial sites with at least two strengths of binding: a weak, temperature-independent binding which could be easily dissociated by rinsing in Krebs-Ringer buffer, and a stronger, temperature-dependent binding which could be dissociated by rinsing in albumin, but not in Krebs-Ringer buffer. Analogous binding of micellar palmitic acid occurred in a brush border preparation of proximal intestine which was devoid of any fatty acid esterifying activity. This suggested that the reversible binding of fatty acid by the intestinal mucosa may be a property of its superficial components, namely the glycocalyx or microvillous membranes, and that it may be independent of the esterifying capacity of the tissue.

Animals↗
PubMed1984

Studies on the metabolic fate of sucrose esters in rats.

The metabolism in rats of sucrose esters of stearic acid and palmitic acid was studied in vivo and in vitro using esters labelled with 14C at the sucrose of fatty-acid moiety. In excretion studies, the ratio of expired radioactivity to absorbed radioactivity after oral administration of the sucrose esters labelled at the sucrose moiety was similar to that after the administration of [14C]sucrose. A similar correlation between the ester labelled at the fatty-acid moiety and the free [14C]fatty acid was also observed. No intact sucrose ester was detected in the urine. Studies in vitro using everted intestinal sacs showed that there was virtually no transport of 14C-labelled sucrose esters from the mucosal to the serosal solution through the intestinal tissues, and that the enzymes in the intestinal mucosa played a more important role in the hydrolysis of sucrose esters than did those in the digestive fluid. In studies of intestinal absorption through the mesenteric lymphatic system, during the 24 hr after ingestion 1.8% of the administered radioactivity was recovered in the lymph after dosing with [U-14C]sucrose monostearate whereas 20% was recovered in the lymph after dosing with sucrose [1-14C]monostearate. This difference in levels of recovery of administered radioactivity indicated that sucrose monostearate was absorbed only after hydrolysis. No intact ester was detected in the lymph or in the portal or femoral blood. The results of all of these experiments show that the sucrose esters are hydrolysed to sucrose and fatty acids prior to intestinal absorption.

Absorption↗
PubMed1989

Divergent fate of unsaturated and saturated ceramides and sphingomyelins in rat liver and cells in culture.

The metabolism of sphingomyelins and ceramides with defined labeled fatty acids was compared after injection in vivo or incubation with cultured cells. The liver was the major site of uptake of sphingomyelins and ceramides with 18:2 or 16:0 fatty acids, but with both sphingolipids a higher recovery of radioactivity was found with 16:0 species. The distribution of radioactivity among liver lipids showed that 1.5 h after injection of 18:2 sphingomyelin, only 21% of the label was found as sphingomyelin, and this value was 37% in the case of 16:0 sphingomyelin. There was a very marked difference in the metabolism of 18:2 and 16:0 ceramides. After injection of 18:2 ceramide only 14% of the radioactivity was recovered as sphingomyelin, and this value was more than 50% with 16:0 ceramide. [14C]18:2 ceramide was converted also to glucoceramide and hydrolyzed more extensively than 16:0 ceramide. These observations were extended to sphingomyelins and ceramides with other fatty acids, using Hep-G2 cells in culture. Significantly more radioactivity was recovered as labeled sphingomyelin after incubation with 16:0, 18:0, 20:0 and 24:0 sphingomyelins than with 18:1 and 18:2 sphingomyelins, while more labeled phosphatidylcholine and phosphatidylethanolamine were found with the unsaturated sphingomyelins. In analogy to the findings in vivo, in the Hep-G2 cells more 16:0, 18:0 and 24:0 ceramides were converted to sphingomyelin than 18:1 or 18:2 ceramides. These differences were also seen with cultured macrophages, in which a more marked reutilization for sphingomyelin formation was found with the saturated ceramide series. The sphingomyelin liposomes were tested also for their capacity to mobilize cholesterol, and a rise in plasma unesterified cholesterol occurred after injection of 18:2 sphingomyelin. Marked enhancement of cholesterol efflux from cholesterol ester-loaded macrophages was also seen with 18:1 and 18:2, 20:0 sphingomyelin in the presence of delipidated high-density lipoprotein. The present results demonstrate that the metabolic fate of sphingolipids is related to their fatty acid composition. While ceramides with saturated fatty acids are predominantly reutilized for sphingomyelin formation, those with unsaturated fatty acids undergo probably more rapid hydrolysis with liberation of fatty acids and channeling into glycerolipids.

Animals↗
PubMed1979

Incorporation and metabolism of [14C]-arachidonic acid in guinea-pig lungs.

1 Following infusion of [(14)C]-arachidonic acid into guinea-pig isolated lungs more than half the administered radioactivity was retained by the lung.2 The majority of the retained radioactivity was present in the phospholipid fraction with lesser amounts in the neutral lipid and free fatty acid fractions. When fatty acid methyl esters of the phospholipid fraction were prepared, 80% of the radioactivity co-chromatographed with methyl arachidonate.3 Transformation to cyclo-oxygenase products and subsequent emergence in lung effluent accounted for approximately 20% of infused radioactivity.4 After pretreatment of lungs with [(14)C]-arachidonic acid, stimulation of arachidonic acid metabolism with injections of partially purified slow-reacting substance of anaphylaxis (SRS-A), bradykinin or antigen challenge released rabbit aorta contracting substance (RCS) and prostaglandin-like substances (PGLS) but little radioactivity. Furthermore, repeated injections of SRS-A or bradykinin released similar amounts of RCS and PGLS but diminishing amounts of radioactivity.5 These data indicated that exogenous arachidonic acid was taken up by the lung and incorporated into phospholipids. However, this newly incorporated arachidonic acid had not equilibrated with the pool activated by SRS-A, bradykinin and antigen challenge for conversion to cyclo-oxygenase products.

Animals↗
PubMed1967

Effect of hypophysectomy and replacement therapy on fatty acid metabolism in the rat testis.

1. The influence of pituitary gonadotrophins and of testosterone on the conversion of linoleic acid into other polyunsaturated fatty acids by rat testicular tissue was studied. 2. In immature hypophysectomized rats, follicle-stimulating hormone caused a threefold increase in the incorporation of radioactivity from [1-(14)C]linoleic acid into testicular lipids; the distribution of (14)C in the polyunsaturated fatty acids, however, was not significantly affected. 3. In mature hypophysectomized rats, the hormonal treatments had less pronounced effects on (14)C incorporation into testicular lipids, but caused a significant increase in the percentage of (14)C incorporated into polyunsaturated fatty acids of the omega-6 series, luteinizing hormone and testosterone having the more pronounced influences. 4. A time-course study of the appearance of radioactivity in the ejaculated spermatozoa of rabbits, after they had been given a tracer dose of [1-(14)C]linoleic acid, indicated that incorporation of radioactivity into spermatozoa occurred during all stages of spermatogenesis.

Aging↗
PubMed1984

One-dimensional thin-layer chromatographic separation of the lipids involved in arachidonic acid metabolism.

A one-dimensional thin-layer chromatographic separation technique is described that separates the phospholipids and neutral lipids that are principally involved in arachidonic acid metabolism from each other, and from arachidonic acid and its eicosanoid derivatives. The technique is useful in studies on changes in arachidonic acid metabolism following cell stimulation. Balance sheets may be drawn up between the loss of radioactivity from phospholipids, and the gain in free fatty acid, eicosanoids, and esterified lipids of the phosphatidylinositol cycle.

Animals↗
PubMed1986

Metabolism of cerebrosides and sulfatides in the nervous system of Xenopus tadpole during metamorphosis.

Xenopus laevis tadpoles undergoing metamorphosis were used to study the turnover of cerebrosides and sulfatides in the nervous system of the frog. Tadpoles at the beginning of metamorphosis were treated by intraperitoneal injection with [U-14C]glucose and radioactivity incorporated into galactosphingolipids of brain and tail was measured after various times. The specific activity of brain cerebrosides increased rapidly for the first 24 hr after injection, reached a plateau after 48 hr, and then declined 40% by 7 days. The specific activity of sulfatides changed somewhat more slowly. Hydroxy fatty acid-containing galactosphingolipids had nearly twice the specific activity compared with their nonhydroxy counterparts in brain. Despite the complete regression of tail nerve cord, metabolism of glycosphingolipids in this tissue also indicated active synthesis as well as degradation during this period. The specific activities of these lipids were similar and all reached a peak 24 hr after injection. Examination of the components of these galactosphingolipids disclosed that only a small fraction (7-25%) of the radioactivity was in the galactose moiety in both brain and tail. The ratios of the radioactivity in fatty acid to that in the sphingoid base were much higher for hydroxycerebroside and hydroxysulfatide than for the nonhydroxy isomers.

Animals↗
PubMed1970

Metabolic turnover of the polar lipids of Mycoplasma laidlawii strain B.

The fatty acyl groups of the membrane polar lipids of Mycoplasma laidlawii B were radioactively labeled by growth in the presence of (14)C-palmitic, oleic, or linoleic acids. No loss of radioactivity from any of the polar lipids occurred during incubation of radiolabeled cells in growth medium containing various nonradioactive fatty acids, although growth and lipid biosynthesis continued throughout the incubation period. The metabolism of the glucose and phosphate moieties was also studied in a similar fashion by utilizing growth in (14)C-glucose or (32)P-inorganic phosphate to radioactively label these groups. As before, no loss of radioactivity from any of the polar lipids occurred during subsequent growth in medium containing unlabeled glucose or phosphate. The results establish that the glyco- and phospholipids of M. laidlawii B are metabolically stable in actively growing cells. The absence of metabolic turnover is discussed in terms of proposed relationships between lipid metabolism and function in this organism.

Carbon Isotopes↗
PubMed1976

Biosynthetic labelling of membrane lipids of eukaryotic cells in tissue culture by a novel type of fluorescent fatty acids.

W-Anthryl labelled fatty acids with hydrocarbon chains of different lengths (C8, C11, C15) and different degrees of unsaturation have been incorporated into the membrane lipids of three different cell lines in tissue culture by addition of these 3H-labelled precursor fatty acids to the growth medium. The cell lines were baby hamster kidney cells (BHK 21), Chang liver cells and the RN6 cell line derived from a chemically induced Schwannoma tumor cell clone. Cell growth was normal. The quantitative analysis on the basis of radioactivity determinations demonstrated that the fluorescent-labelled fatty acids were introduced into the neutral lipid fraction (triglycerides, diglycerides, and cholesterol esters, all present in small amounts), but mainly into the phospholipid classes phosphatidylcholine, -ethanolamine and -serine, and to a lesser extent, as N-acyl component of sphingolipids (sphingomyelins, ceramides, mono- and diglycosylceramides). Cell fractionation studies indicated that the membranes of all subcellular particles were labelled with the fluorescent probes in their lipid moieties. These w-anthryl fatty acids are the first type of fluorescent lipid precursors which can be incorporated biosynthetically in vivo into membrane lipids of eukaryotic cells. The effective incorporation of the bulky fluorescent anthryl group in the terminal position of fatty acids of different chain lengths into the complex membrane lipids of the cell gives proff of 1) their uninhibited membrane transport, 2) their activation by the acyl-CoA synthetase and 3) their substrate properties for the O- acyl and N-acyl transferases in phospho- and sphingolipid biosynthesis.

Animals↗
PubMed1976

Triacylglycerol turnover in Tetrahymena pyriformis. Relation to phospholipid synthesis.

The metabolic function of triaclyglycerol in Tetrahymena pyriformis was investigated by prelabeling endogenous lipid with a 14C-labeled short chain fatty acid, and then following the disappearance of radioactivity from triacylglycerol and its appearance in other products. In 90 min, up to 85% of the label in triacylglycerol turns over, and although some radioactivity appears in CO2 and glycogen, most of the label appears in phospholipid. Starvation of the cells, as well as resuspension in enriched medium or provision of acetate all block triacylglycerol breakdown, while supplementation of the medium with pyruvate does not. Prelabeling lipid with [3H] glycerol shows that some of the transfer of material from triacylglycerol to phospholipid involves transfer of the glycerol backbone, although transfer of triacylglycerol fatty acids directly to phospholipid probably also occurs. In addition, the catabolism of triacylglycerol occurs by a "last-in-first-out" mechanism, indicating some form of compartmentation of triacylglycerol in this cell. The results demonstrate an important metabolic interrelationship between triacylglycerol catabolism and phospholipid synthesis and raise the question, in this cell at least, of the validity of considering triacylglycerol only as a fuel storage form.

Acetates↗
PubMed1983

Biochemical and electron microscope radioautographic study of intestinal absorption of tritiated palmitic and oleic acids in control and actidione-cycloheximide-treated rats.

Intestinal absorption of tritiated palmitic and oleic acids was investigated in control and actidione-cycloheximide-treated rats. Pancreatic juice was collected and 24 hr later an intestinal loop was cannulated in situ. A 90 mumole-lipid emulsion composed of an equimolar mixture of monopalmitin, palmitic and oleic acids with bile was infused with either 3H-labeled palmitic or oleic acid. After 15 or 30 min biochemical analysis was carried out to follow the uptake and the transfer of the labeled fatty acids. Mucosa was removed for both biochemical analysis of lipid classes and the ultrastructural or radioautographic electron microscope study depending on the radioactive activity. Following actidione-cycloheximide treatment, the uptake of both fatty acids decreased, but the amount of lipids in the mucosa greatly increased, while amount of the reesterification of fatty acids in the mucosa diminished. Consequently the amount of infused palmitic acid which was transferred in 15 min decreased from 36% in the absence of treatment to 4.6% when treatment was used. The corresponding figures for oleic acid are 70% and 20.9%. Unstructured lipids were in the intercellular spaces, indicating that a cytotoxic effect had occurred which produced a defect in the lipoprotein particle organization. The Golgi complex, in the final step of the chylomicron synthesis before exocytosis, showed low level of radioautographic reaction indicating less participation by the complex in lipid transfer. The various processes which were inhibited during long-chain fatty acid absorption from the luminal area to the Golgi complex included fatty acid binding by proteins, enzymatic acylation and esterification, apoprotein participation. This inhibition explains why long-chain fatty acid absorption was greatly impaired. Moreover, our observations compared with those obtained during decanoic acid absorption, particularly our radioautography based observations, emphasize the important role of the Golgi complex which requires intense membrane turnover during lipid absorption.

Animals↗
PubMed1986

Mathematical model of the metabolism of 123I-16-iodo-9-hexadecenoic acid in an isolated rat heart. Validation by comparison with experimental measurements.

The aim of the present study was to demonstrate that it is possible to estimate the intracellular metabolism of a fatty acid labelled with iodine using external radioactivity measurements. 123I-16-iodo-9-hexadecenoic acid (IHA) was injected close to the coronary arteries of isolated rat hearts perfused according to the Langendorff technique. The time course of the cardiac radioactivity was measured using an INa crystal coupled to an analyser. The obtained curves were analysed using a four-compartment mathematical model, with the compartments corresponding to the vascular-IHA (O), intramyocardial free-IHA (1), esterified-IHA (2) and iodide (3) pools. Curve analysis using this model demonstrated that, as compared to substrate-free perfusion, the presence of glucose (11 mM) increased IHA storage and decreased its oxidation. These changes were enhanced by the presence of insulin. A comparison of these results with measurements of the radioactivity levels within the various cellular fractions validated our proposed mathematical model. Thus, using only a mathematical analysis of a cardiac time-activity curve, it is possible to obtain quantitative information about IHA distribution in the different intracellular metabolic pathways. This technique is potentially useful for the study of metabolic effects of ischaemia or anoxia, as well as for the study of the influence of various substrates or drugs on IHA metabolism in isolated rat hearts.

Animals↗