Absence of effect of caffeine on the thyroid in the Syrian golden hamster: results of a 90-day study

Caffeine in drinking water was offered ad lib. to male and female Syrian golden hamsters (Mesocricetus auratus W) for 90 days. Animals were randomly assigned to three dose groups (91.3, 274 and 822 mg/litre) and one control group (filtered tap water), each consisting of 20 male and 20 female animals. In relation to body weight, mean caffeine consumption was higher in females (low dose: 14.7; medium dose: 50.8; high dose: 104.8 mg/kg body weight/day) than males (low dose: 9.0; medium dose: 24.6; high dose: 65.2 mg/kg body weight/day). Caffeine in plasma was measured after 3 days, 3 wk and 3 months of treatment. As expected from calculation of the caffeine intake, mean values were higher in females (low dose: 0.6; medium dose: 3.6; high dose: 7.2 mg/litre) than in males (low dose: 0.4; medium dose: 0.7; high dose: 2.9 mg/litre). After 3 days of treatment, a transient, non-dose-related increase in mean (SEM) tri-iodothyronine (n=10) was found in the medium and high-dose (751+/-23 and 742+/-25 ng/litre, respectively) groups of males compared with that in the controls (610+/-39 ng/litre)(P<0.05). The values measured at later time points (days 24 and 91) were similar in all groups. No treatment-related changes were found in thyroxine (days 3, 24 and 91) and other clinicochemical analytes (day 91), absolute and relative adrenal weight (day 91), gross pathology and thyroid histopathology (day 91). In conclusion, no signs of thyroid toxicity of caffeine were observed in the Syrian golden hamster.

The somatic white-ivory eye spot test does not detect the same spectrum of genotoxic events as the wing somatic mutation and recombination test in Drosophila melanogaster

A groups of six chemical compounds was tested in parallel in two different somatic genotoxicity assays in Drosophila melanogaster, the wing somatic mutation and recombination test (SMART) and the white-ivory eye spot test. The wing spot test makes use of the wing cell markers multiple wing hairs (mwh) and flare (flr) and detects both mitotic recombination and various types of mutational events. The white-ivory eye spot test makes use of the white-ivory (wi) quadruplication and detects the somatic reversion of the recessive eye color mutation wi to the wild-type (w+). Three- or two-day-old larvae were fed chronically with the compounds ethylnitrosourea (ENU), N-nitrosopyrrolidine (NNP), caffeine (CAF), chromium (VI) oxide (CRO), potassium chromate (POC), and 2,4-dichlorophenoxyacetic acid (2,4-D). All six compounds are genotoxic to various degrees in the wing spot test. The percentage of the genotoxic activity that is due to mitotic recombination was between 84% and 91% for the hexavalent chromium compounds CRO and POC and about 68% for 2,4-D. In contrast, ENU and NNP showed only 46% and 25% recombinagenic activity, respectively. In the white-ivory eye spot test, the three compounds (CRO, POC, and 2,4-D) with high recombinagenic activity and CAF were clearly nongenotoxic, whereas only ENU and NNP gave a positive response. From these results, it is concluded that the spectrum of genotoxic events detected by the two assays is different. In particular, the white-ivory eye spot test appears not to detect mitotic recombination the way the wing spot test does.

Comet assay studies indicate that caffeine-mediated increase in radiation risk of embryos is due to inhibition of DNA repair

It is well known that under specific conditions caffeine is able to enhance radiation risk of mammalian cells by a factor of approximately 1.5-2. Various mechanisms are discussed in the literature as possible explanations for this interaction. Inhibition of DNA repair plays a crucial role in the discussion, although direct evidence for this assumption is difficult to obtain. We used the "comet assay' in order to analyse the significance of repair inhibition by caffeine in the two-cell stage of mammalian gestation. Our data show that at the concentration necessary for increasing radiation risk (2 mM), caffeine effectively inhibits the restitution of radiation-damaged DNA.

Inhibitors in tea of intestinal absorption of phenylalanine in rats

This work studies the effect of tea extract on the mucosal and serosal transport of phenylalanine, and attempts to identify the active ingredient(s) therein by studying the effect of known tea constituents like theophylline, caffeine and tannic acid. Tea and all the constituents tested inhibited the mucosal uptake of phenylalanine. The serosal transport was unaffected by caffeine and tannic acid, but inhibited by theophylline and high concentrations of tea. The in vitro activity of the intestinal Na+-K+ATPase was also assayed from a jejunal homogenate in presence of theophylline, caffeine, tannic acid and cAMP. All were found to inhibit significantly the enzyme. The in vitro activity of a purified Na+-K+ATPase was however stimulated by theophylline and caffeine, and inhibited only by tannic acid. It was concluded that the inhibitory effect of tea is exerted mainly through its constituents which inhibit the Na+-K+ pump directly (tannic acid) or indirectly (theophylline and caffeine), possible by elevating cAMP levels, dissipating thus the sodium gradient needed for the mucosal uptake of the amino acid.

Delayed effects of ethanol, caffeine and nicotine assessed by wheel-running and drinking in mice

Effects of ethanol, caffeine and nicotine, pleasurable substances, on wheel-running and drinking in mice that were housed under a 12 : 12-hr light-dark schedule (lighting period ; 6 : 00-18 : 00) were investigated. All drug administrations were carried out at 11: 00, a mid-light period. Although ethanol (0.8-2.4 g/kg p.o.) scarcely changed both the wheel-running and drinking during the light period, it was followed by a strong suppression of both behaviors during the coming dark period (18 : 00-6 : 00). The same treatment with caffeine (1-10 mg/kg s.c.) produced significant increase in the drinking during the light period, but suppression of the wheel-running during the dark period. Nicotine (0.1-1 mg/kg s.c.) significantly suppressed the wheel-running, but not drinking, during the dark period. The coadministration of nicotine (0.1-1 mg/kg) with ethanol (2.4 g/kg) reduced the behavioral suppression during the dark period. Whereas nicotine (0.1-1 mg/kg) reduced the increased drinking during light period by caffeine (10 mg/kg), but enhanced the caffeine-induced behavioral suppression during the dark period. These results indicate that the administration of pleasurable substances in the mid-light period results in a delayed effect which is characterized by a suppression of either and/or both wheel-running and drinking during the coming dark period starting 7 hr after the administration, and that nicotine acts to antagonize the effect of ethanol, but contrally to enhance the effect of caffeine.

Neonatal caffeine exposure alters seizure susceptibility in rats in an age-related manner

Early developmental exposure to caffeine in rats results in decreased susceptibility to certain chemically-induced seizures in the adult. To determine whether this effect first appears in adulthood or is present during preceding developmental stages, we exposed neonatal rats to caffeine and determined seizure thresholds in animals 28, 42 and 70-90 days of age. Rats were unhandled or received either vehicle (water) or caffeine (15-20 mg/kg/day) by gavage (0.05 ml/10 g) over postnatal days 2-6. At 28, 42, or 70-90 days of age, rats were infused intravenously with picrotoxin (PIC), bicuculline (BIC), pentylenetetrazol (PTZ), caffeine (CAFF), strychnine (STR), or kainic acid (KA). Seizure thresholds for each compound were analyzed as a function of neonatal treatment, sex, and age. At 28 days, neonatally caffeine-exposed rats had a higher seizure threshold only for PTZ (P < 0.03). At 42 days, neonatally caffeine-exposed rats had higher seizure thresholds for PIC (P < 0.0007) and PTZ (P < 0.0001) than did controls. These results at 28 and 42 days are compared with previously reported data that demonstrated that in adulthood, rats neonatally exposed to caffeine have higher thresholds for seizure induction with CAFF, PTZ, and KA. Thus, early developmental exposure to caffeine results in decreases in seizure susceptibility that are agent specific and may result in a delay in the decrease in seizure threshold that occurs for many agents between late juvenile ages and adulthood.

[The effect of Val'kofen tablets for children on the function of the gastrointestinal tract and liver in an experiment]

It was prepared new child's medicinal form, the tablets "Valcophene" for making a wider variety of pediatric preparation's. It is studied the influence of "Valcophene" on the functional state of alimentary canal in experiment on rat's. Results investigation's are testified to absence of ulcerative action in new child's preparations. Studying influence in liver functional state is provided for new children's preparation "Valcophene" too. The chronic experiment is showed that "Valcophene" didn't influence on liver in experimental animals.

The effect of forskolin on the teratogenicity of methylxanthines in the chick embryo heart

Interactions between forskolin and methylxanthines, including caffeine and isobutylmethylxanthine (IBMX), in the developing chick embryo heart were investigated. Forskolin, a potent activator of adenylate cyclase, was administered to young chick embryos (Hamburger-Hamilton stage 24) together with caffeine or IBMX at doses where each agent alone caused minimal embryotoxicity. The incidence of malformation in the embryonic chick heart or aorta induced by caffeine (5 x 10(-7) or 5 x 10(-6) mol) and IBMX (1 or 2.5 x 10(-6) mol) significantly increased with coadministration of forskolin (1 x 10(-9) mol). Cardiovascular malformations included ventricular septal defect, double outlet right ventricle, and aortic arch anomalies. These results indicate that forskolin potentiates the teratogenicity of caffeine or IBMX on the cardiovascular system in the chick embryo and suggest that this potentiation may be related to increase intracellular cAMP due to stimulation of adenylate cyclase (forskolin) and inhibition of phosphodiesterase (methylxanthines).

Effects of the dopamine autoreceptor antagonist (-)-DS121 on the discriminative stimulus properties of d-amphetamine and cocaine

(-)-DS121 [S-(-)-3-(3-cyanophenyl)-N-n-propyl piperidine) is a recently synthesised phenylpiperidine derivative suggested to be a dopamine receptor antagonist acting preferentially at dopamine autoreceptors. The drug exerts 'agonist-like' behavioural effects by enhancing dopamine release, but also shares properties in common with neuroleptics. The ability of (-)-DS121 to both generalise to and antagonise the stimulus effects of psychostimulants was determined in rats trained to discriminate d-amphetamine (0.5 mg/kg) or cocaine (5.0 mg/kg) from saline in a two-lever, food-reinforced, drug discrimination task. (-)-DS121 (3.5-14.0 mg/kg) produced small, but significant, increases in drug lever-appropriate responding in both d-amphetamine and cocaine-trained rats. However, there was no indication of a dose-dependent effect in either case. On the other hand, (-)-DS121 dose-dependently reduced response rate. Caffeine produced a higher level of drug lever-appropriate responding than (-)-DS121 in d-amphetamine-trained rats. (-)-DS121 (7.0-14.0 mg/kg) also weakly antagonised the cueing properties of both d-amphetamine and cocaine. A marked response disruption with the drug combination precluded testing of higher doses of (-)-DS121. A combination of subthreshold doses of (-)-DS121 (3.5 mg/kg) and d-amphetamine (0.0625 mg/kg) produced a significant degree of drug lever-appropriate responding, suggesting a synergistic interaction between these drugs. However, such an interaction was not noted with a higher dose of (-)-DS121, or when this drug was administered with a low dose of cocaine (0.25 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal exposure to alcohol plus caffeine in rats: pregnancy outcome and early offspring development

The factors determining susceptibility to fetal alcohol syndrome (FAS) are not fully understood. We used an animal model of alcohol-related birth defects to assess the coteratogenic potential of caffeine as a risk factor in FAS. Rats were exposed prenatally to alcohol (approximately 15 g/kg/day) with or without caffeine (approximately 84 mg/kg/day) from gestation days 6 through 20 via liquid diet. All control groups were pair-fed to the alcohol-exposed groups. In addition, some controls had free access to lab chow and water. Prenatal exposure to alcohol or caffeine reduced both maternal weight gain during pregnancy and birth-weight of offspring. The combination of alcohol plus caffeine produced an additive effect in reducing birthweight and synergistic effects in increasing postnatal offspring mortality. Prenatal alcohol exposure had a significant negative impact on several developmental indices, including grip strength and negative geotaxis. Prenatal caffeine exposure did not affect maturational measures and did reduce offspring serum levels of the zinc-dependent enzyme alkaline phosphatase. This study in rats demonstrated that caffeine can exacerbate some of the effects of alcohol on prenatal development, specifically reduced birthweight, litter size, and postnatal survival, but that caffeine does not appear to alter prenatal alcohol-induced delays in early postnatal maturation of survivors. The relative impact of intralitter birthweight rank on developmental outcome was also assessed.

Analysis of the potential carcinogenicity of coffee and its related compounds in a medium-term liver bioassay of rats

The potential carcinogenicity of coffee and related compounds was examined using a medium-term liver bioassay based on the induction of glutathione S-transferase placental form (GST-P)-positive foci in F344 rats. A total of 230 males were initially injected with diethylnitrosamine (200 mg/kg body weight, ip) or saline as controls and 2 wk later were fed on diet or drinking water supplemented as follows for 6 wk: 5% regular instant coffee; 5% decaffeinated instant coffee; freshly brewed coffee, 8 g in 140 ml water; 0.1% caffeine, 0.2% methylglyoxal, 0.2% glyoxal; or 0.3% theophylline in the drinking water (w/v); and 0.4% theobromine in the diet (w/w). All rats were subjected to two-thirds partial hepatectomy at wk 3 and killed at wk 8. The resultant values for GST-P-positive hepatic focus induction were slightly increased with methylglyoxal and decreased with glyoxal and theobromine compared with the corresponding controls. Although the increase in number of foci for methylglyoxal was statistically significant at P < 0.05, the value was within the historical control levels. Regular and decaffeinated instant coffee as well as fresh-brewed coffee, caffeine and theophylline exerted no effects on focus development. Thus, the coffee-related compounds examined demonstrated no obvious enhancing potential, and it is therefore concluded that coffee and its main constituents are not carcinogenic for the rat liver.

Effects of caffeine on glandular stomach carcinogenesis induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine and sodium chloride

The modifying effects of caffeine ingestion on glandular stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and sodium chloride (NaCl) were investigated in male Wistar rats. Animals were given a MNNG solution (100 ppm) as their drinking water and simultaneously fed a diet supplemented with 5% NaCl for 8 wk. They then received 0.25% caffeine solution (groups 1 and 3) or tap water (groups 2 and 4) as the drinking water, and were fed the NaCl diet (groups 1 and 2) or basal diet (groups 3 and 4) for the following 32 wk. Both caffeine and NaCl treatments exerted growth retardation effects, the suppression being stronger with caffeine than NaCl, and animals in group 1 (NaCl plus caffeine) showing the lowest body weight. The incidence of adenocarcinomas in the pylorus was significantly decreased in group 1 compared with the group 2 (NaCl) value (P < 0.05). The incidence of atypical hyperplasias in the fundus was also lower in group 1 than in group 2, although in both cases significantly higher (P < 0.05 and P < 0.01) than in group 4 (no treatment). These results were in good agreement with short-term assay findings whereby lipid peroxidation in the glandular stomach mucosa induced by 4% NaCl ingestion was inhibited by caffeine treatment. In group 3 (caffeine), caffeine intake by itself did not modulate glandular stomach tumour development. The results thus suggest that caffeine inhibits the gastric tumour promotion activity of NaCl in rats.

Caffeine potentiates or protects against radiation-induced DNA and chromosomal damage in human lymphocytes depending on temperature and concentration

The effect of caffeine on radiation-induced chromosomal aberrations and DNA strand breaks in unstimulated human lymphocytes was investigated. When present prior to and during the radiation exposure, caffeine treatment was found to cause either potentiation or protection against induction of chromosomal aberrations depending on the concentration and temperature. When the nucleoid sedimentation technique was applied, enhancement or reduction of radiation-induced DNA strand breaks by caffeine was also found to be dependent on temperature and caffeine concentration. It is proposed that caffeine, in addition to its suspected ability to influence DNA repair, can also influence the induction of DNA damage, leading to alterations in the yield of chromosomal aberrations.

Potential teratogenic and neurodevelopmental consequences of coffee and caffeine exposure: a review on human and animal data

The teratogenic effect of caffeine has been clearly demonstrated in rodents. The sensitivity of different animals species is variable. Malformations have been demonstrated in mice at 50-75 mg/kg of caffeine, whereas the lowest dose usually needed to induce malformations is 80 mg/kg in rats. However, when caffeine is administered in fractioned amounts during the day, 330 mg/kg/day are necessary to reach teratogenicity in rats. In rodents, the most frequently observed malformations are those of the limbs and digits, ectrodactyly, craniofacial malformations (labial and palatal clefts) and delays in ossification of limbs, jaw and sternum. Nevertheless, even in rodents, caffeine can be considered as a weak teratogenic agent, given the quite large quantities of caffeine necessary to induce malformations and the small number of animals affected. In humans, caffeine does not present any teratogenic risk. The increased risk of the most common congenital malformations entailed by moderate consumption of caffeine is very slight. However, caffeine potentiates the teratogenic effect of other substances, such as tobacco, alcohol, and acts synergistically with ergotamine and propranolol to induce materno-fetal vasoconstrictions leading to malformations induced by ischemia. Therefore, even though caffeine does not seem to be harmful to the human fetus when intake is moderate and spread out over the day, some associations, especially with alcohol, tobacco, and vasoconstrictive or anti-migraine medications should be avoided. Maternal consumption of caffeine affects brain composition, especially in case of a low-protein diet and also seems to interfere with zinc fixation in brain. Maternal exposure to caffeine induces also long-term consequences on sleep, locomotion, learning abilities, emotivity, and anxiety in rat offspring, whereas in humans, more studies are needed to ascertain long-term behavioral effects of caffeine ingestion by pregnant mothers.

Effects of caffeine and related methylxanthines on fetal mouse palates cultured in vitro

The maxillary regions of day-12.5 ICR mouse fetuses were cultured in a chemically-defined serumless medium and the effects of methylxanthine derivatives on cultured palates were studied. Explanted palates were treated for 72 hr in vitro with 0.5-2 mM caffeine (CA), 1-2 mM theophylline (TP), or 1-2 mM theobromine (TB). Although the three compounds tested did not prevent the contact of opposing palatal shelves, palatal fusion was inhibited by CA and TP at a concentration of 2 mM, and the inhibitory effect of CA was more evident than that of TP. On the other hand, TB did not exert an inhibitory effect on palatogenesis at 2 mM. Since the in vitro toxicity of the methylxanthine compounds appeared to correlate well with their in vivo teratogenic potential, the organ culture method of fetal rodent palates should be a useful tool for screening teratogenic agents, especially those causing cleft palate.

Induction of DNA double-strand breaks by 8-methoxycaffeine: cell cycle dependence and comparison with topoisomerase II inhibitors

We have studied the ability of 8-methoxycaffeine (8-MOC)--one of the most effective caffeine derivatives in inducing chromosomal aberrations--to induce DNA double strand breaks (DSB) in purified human T lymphocytes during the cell cycle. Etoposide- or ellipticine-mediated DNA break frequency was used as a parameter of topoisomerase II activity. DNA-DSB induced by either 8-MOC or VP16 or ellipticine rose co-ordinately with the level of DNA topoisomerase II and with the onset of DNA replication. At concentrations between 10 and 50 microM 8-MOC was approximately 75% as active in terms of DSB as VP16 and ellipticine. By contrast with VP16 and ellipticine, 8-MOC was not cytotoxic. In conclusion, our data suggest that 8-MOC is an agent that efficiently induces DNA-DSB at non-toxic concentrations, and without direct inhibition of topoisomerase II.

Alteration of femoral structure in later life by chronically feeding caffeine during rapid growing period in newborn female rats

The effects of caffeine intake in early life on bone structure later in life were studied in rats. At day 9 of gestation, dams were divided into 2 groups. Group 1 (control) received a 20% protein diet; group 2 received the 20% protein diet supplemented with caffeine (2 mg/100 g body weight). After birth pups were continuously fed their respective diets until day 93, when the diet of group 2 was replaced with a noncaffeine 20% protein diet. On day 388 animals from both groups were weighed, killed, and femora and mandibles were removed. Calcium, phosphorus, magnesium, zinc, hydroxyproline, and hexosamine concentrations were measured. Radiographs of some femora were taken and paraffin cross sections were made at the midshaft of others. Femora in the caffeine group were wider, periosteal bone area/total bone area was greater, the cross sectional area of femoral bone was smaller, and there were fewer osteocytes/bone area than in controls. Calcium, phosphorus, zinc, and hydroxyproline concentrations in the caffeine group were less in both bones of the caffeine group. These results indicate that if animals are exposed to caffeine during the rapidly growing period, changes occur in femoral bone which are similar to those that occur with aging.

Combined effects of caffeine and malnutrition during pregnancy on suckling behavior in newborn rats

Six groups of pregnant dams were fed a 20%, 12%, and 6% protein diet with and without caffeine (2 mg/100 g b.wt.), starting on day 7 of gestation. At day 18 of gestation, randomly selected dams of each group were used to record prenatal fetal behavior. The remaining dams were continuously fed their respective diets until the birth of their pups. Upon delivery, newborn pups from the dams fed a 20%, 12%, or 6% protein diet with caffeine were placed with foster dams that the dietary regimen during gestation was a 20%, 12%, or 6% protein diet, respectively. Dams fed a noncaffeine diet, along with their newborns, were fed their respective diets until day 15. Suckling behavior tests for newborns were conducted on days 2, 8, and 15. On day 15, both nondeprived and deprived newborn rats were studied. Caffeine in combination with a malnourished diet has different effects on general activity in prenatal stages compared to postnatal stages. Our findings support the view that prenatal exposure to caffeine may produce greater effects because: a) caffeine and its metabolites pass freely into the embryo and attain a concentration slightly lower than in the maternal plasma; and b) caffeine may be poorly metabolized during pregnancy, causing an accumulation in the fetal tissues. Prenatal caffeine at the dosage we have used in combination with malnutrition may produce lasting metabolic alterations in the nervous system related to the emergence of suckling behavior and general motor activity.

In vitro study of teratogenic effects of caffeine on cultured rat embryos and embryonic cells

The teratogenic potential of caffeine was examined in vitro by a whole embryo culture system (WECS) and an embryonic cell culture system (micromas teratogen assay: MTA) in the rat. In the WECS, hyperemia of the tail, and a reduction of the placental size was induced by caffeine at concentrations higher than 50 micrograms/ml; hypoplasia of the forelimb bud was induced at concentrations higher than 100 micrograms/ml; hematoma in the yolk sac and dysmorphogenesis of the fore- and hind-limb buds, prosencephalon and tail were induced by 200 micrograms/ml caffeine. In the MTA, even with 200 micrograms/ml caffeine, the toxicological parameters obtained by proliferation and differentiation assays of the midbrain and limb bud cells were almost the same as in the control. In conclusion, caffeine induced various morphological anomalies, but did not affect proliferation or differentiation of cells in these experimental systems.

Evaluation of the genotoxicity data on caffeine

The potential health effects of caffeine have been investigated for over two decades in a variety of model systems including limited human populations. Thus, it is probably one of the most extensively studied natural occurring dietary chemicals. One area which has received a great deal of attention is the potential genotoxic property of caffeine. To better understand whether caffeine itself or in combination with other agents exhibits genotoxic effects, hundreds of research studies published over the past 5 years have been reviewed. These studies have utilized a number of animal, prokaryotic, eukaryotic, and mammalian cell culture model systems. They have investigated the effects of caffeine alone or in combination with other physical and chemical agents on many aspects of cell division, chromosome stability, toxicity, and mutagenicity. A number of effects have been observed. However, they usually appear after very high doses (> 1 mM) of caffeine in combination with genotoxins, and are usually specific to certain cell types and/or cellular parameters. Humans, on the other hand, consume much less caffeine in the diet, with peak serum levels in the micromolar range 10- and 1000-fold higher compared to levels in animal and cell culture models. Thus, it is difficult to implicate caffeine, even at the highest levels of dietary consumption, as a genotoxin to humans.

The point mutation Arg615-->Cys in the Ca2+ release channel of skeletal sarcoplasmic reticulum is responsible for hypersensitivity to caffeine and halothane in malignant hyperthermia

Malignant hyperthermia (MH) is an autosomal dominant myopathy. Molecular genetic studies have shown that the alteration of Arg615 to Cys in the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum (ryanodine receptor) is cosegregated with porcine MH (Fujii, J., Otsu, K., Zorzato, F., de Leon, S., Khanna, V. K., Weiler, J. E., O'Brien, P. J., and MacLennan, D. H. (1991) Science 253, 448-451; Otsu, K., Khanna, V. K., Archibald, A., and MacLennan, D. H. (1991) Genomics 11, 744-750). Here, using the fluorescence calcium indicator indo-1, we determined the concentration of ionized cytosolic calcium in myoblastic cells transfected with either the wild-type or mutated ryanodine receptor cDNA. The cells expressing the mutant ryanodine receptor showed higher sensitivity to caffeine, which induces Ca2+ release from the sarcoplasmic reticulum through the ryanodine receptor. Exposure to clinical doses of halothane resulted in a rapid increase of [Ca2+]i in cells expressing the mutated ryanodine receptor, whereas no [Ca2+] changes were observed in cells expressing the wild-type ryanodine receptor. These results provide definite evidence that a single amino acid mutation, Arg615-->Cys, in the ryanodine receptor is causative of MH.

Potential genotoxic, mutagenic and antimutagenic effects of coffee: a review

Coffee and caffeine are mutagenic to bacteria and fungi, and in high concentrations they are also mutagenic to mammalian cells in culture. However, the mutagenic effects of coffee disappear when bacteria or mammalian cells are cultured in the presence of liver extracts which contain detoxifying enzymes. In vivo, coffee and caffeine are devoid of mutagenic effects. Coffee and caffeine are able to interact with many other mutagens and their effects are synergistic with X-rays, ultraviolet light and some chemical agents. Caffeine seems to potentiate rather than to induce chromosomal aberrations and also to transform sublethal damage of mutagenic agents into lethal damage. Conversely, coffee and caffeine are also able to inhibit the mutagenic effects of numerous chemicals. These antimutagenic effects depend on the time of administration of coffee as compared to the acting time of the mutagenic agent. In that case, caffeine seems to be able to restore the normal cycle of mitosis and phosphorylation in irradiated cells. Finally, the potential genotoxic and mutagenic effects of the most important constituents of coffee are reviewed. Mutagenicity of caffeine is mainly attributed to chemically reactive components such as aliphatic dicarbonyls. The latter compounds, formed during the roasting process, are mutagenic to bacteria but less to mammalian cells. Hydrogen peroxide is not very active but seems to considerably enhance mutagenic properties of methylglyoxal. Phenolic compounds are not mutagenic but rather anticarcinogenic. Benzopyrene and mutagens formed during pyrolysis are not mutagenic whereas roasting of coffee beans at high temperature generates mutagenic heterocyclic amines. In conclusion, the mutagenic potential of coffee and caffeine has been demonstrated in lower organisms, but usually at doses several orders of magnitude greater than the estimated lethal dose for caffeine in humans. Therefore, the chances of coffee and caffeine consumption in moderate to normal amounts to induce mutagenic effects in humans are almost nonexistent.

Antagonizing effect of triphenyltin chloride on cytosine-1-beta-D-arabinofuranoside potentiation of chromosome aberrations induced by mitomycin C

We previously reported that the organotin triphenyltin chloride (TPTC), which has been widely used as an anti-fouling coating for fishing nets and ship bottoms, potentiated clastogen-induced chromosome aberrations during the G2 phase of the cell cycle. In this communication, CHO cells treated with mitomycin C (MMC) were post-treated with TPTC in the presence and absence of other agents--cytosine-1-beta-D-arabinofuranoside (araC), hydroxyurea, or caffeine--having a similar effect during the G2 phase of the cell cycle. The potentiating effect of araC was completely inhibited in the presence of TPTC at the concentration at which TPTC showed its potentiating effect, suggesting that potentiating effects of TPTC and araC are antagonistic. On the other hand, combined treatment with TPTC and caffeine or hydroxyurea showed a potentiating effect almost equal to the sum of the potentiating effects of each given separately.

Enhancement of CDDP cytotoxicity by caffeine is characterized by apoptotic cell death

The ability of caffeine, an agent that suppresses cell replication by inhibiting deoxyribonucleic acids (DNA) repair, to modulate the cytotoxicity of cis-diamminedichloroplatinum (CDDP) was investigated in murine lymphoma cell line EL-4. EL-4 cells were precultured with or without 20 micrograms/ml CDDP for 1 h and then cultured in the presence of 5 mM caffeine up to 48 h after reseeding. In CDDP-pretreated cells, suppression of cell growth and decrease in cell viability from 24 h were observed. Cell cycle arrest in G2 + M phase and a concomitant increase in both rhodamine 123 (R123) uptake and cell size (forward scatter) were observed in these cells. Treatment with caffeine alone suppressed growth rate, R123 uptake, cell size, and frequency of S phase fraction in the cell cycle. Combination of the two agents, CDDP+caffeine, strongly suppressed not only cell viability but also R123 uptake and cell size, compared with CDDP pretreatment alone. DNA histogram analysis by flow cytometry revealed that cultivation with caffeine hastened G2 + M arrest in CDDP-pretreated cells by reduction in the time of passing through S phase. DNA fragmentation was observed following incubation of CDDP-pretreated cells with caffeine for 16 h when marked accumulation in G2 + M phase was observed. The intensity of these ladder fragments increased in a time-related manner. These results demonstrate that enhancement of cytotoxic activity against CDDP-treated cells by caffeine is characterized by an acceleration of DNA degradation in G2 + M phase, namely apoptotic cell death. The fact that induction of DNA fragmentation during G2 + M phase by caffeine modulates the cytotoxicity of CDDP may give rise to a new combination regime of chemotherapy against malignant tumor cells.