Effects of chronic ingestion of caffeine on mammary growth and reproduction in mice

Normal mammary gland growth and reproduction were examined in C3H/HeMei mice given caffeine as drinking water (500 mg/l tap water) after weaning on day 20 of age. Caffeine ingestion had little effects on any of the day of vaginal opening, body growth, pattern of estrous cycles, mammary gland growth and reproduction except for the rearing rate on day 12 of lactation. Five out of 12 mothers given caffeine lost all pups before day 12 and resulted in 51% of the rearing rate on that day, while that of the control was 91%. The rate did not change thereafter in either group. The results indicate that the chronic heavy ingestion of caffeine would induce the high mortality of pups during early stage of lactation.     

Reduction of caffeine teratogenicity in mice by inducing maternal drug metabolism with beta-naphthoflavone

The effect of stimulating maternal drug metabolism on caffeine teratogenicity was investigated in C57BL/6J (cytochrome P1-450 inducible) and AKR/J (cytochrome P1-450 noninducible) mice. The inducing agent, beta-naphthoflavone (beta-NF) in corn oil, was administered intraperitoneally (IP) to dams at 20 or 80 mg/kg/d on days 9 and 10 of gestation. Teratogenic injections of 175 mg/kg/d caffeine in deionized water were administered IP on days 11 and 12 of gestation. All dams were sacrificed on day 18 of gestation, and fetuses were fixed for razor blade sectioning and skeletal examination. Caffeine, without maternal metabolism stimulation, caused similar types and rates of malformations in both strains of mice. Inducing drug metabolism during pregnancy with beta-NF protected the embryos from the congenital toxicities of large injections of caffeine. Reductions in embryolethality, limb malformations, and hematoma formation were evident in the inducible strain but not in the strain incapable of being induced. A dosage of eighty mg/kg/d was more effective than 20 mg/kg/d beta-NF in decreasing malformations, suggesting that stimulation of metabolism and caffeine-induced teratogenicity are inversely related. Rapid elimination of caffeine resulting from increasing drug metabolism with the concomitant decrease in toxicity would indicate that caffeine, and not a metabolite, is the toxicant.     

Potentiating effects of caffeine on teratogenicity of alkylating agents in mice

Teratogenic to subteratogenic doses of x-ray, mitomycin C, MNNG, thio-TEPA, cyclophosphamide, and chlorambucil were administered to pregnant ICR mice together with caffeine at doses of 12.5, 25, or 50 mg/kg on day 11 of gestation. Fetuses were examined for gross malformations on day 18 of gestation. The teratogenicity of mitomycin C was significantly potentiated by caffeine at a dose as low as 12.5 mg/kg. The teratogenicity of chlorambucil was also significantly potentiated by caffeine at 50 mg/kg, but similar potentiation was not observed for x-ray, MNNG, thio-TEPA, and cyclophosphamide.     

Effects of chronic caffeine ingestion on growth and myocardial function

Experiments were conducted to determine whether chronic caffeine consumption during early growth and development affected cardiac performance and development of adipose tissue. Dams were fed a nutritionally complete diet with or without the addition of 10 mg/kg caffeine during lactation. After weaning, the pups were maintained on this diet until they were sacrificed at 88 days of age. Body weight at the time of sacrifice was comparable for both groups. The hearts from caffeine-fed animals were significantly (P less than 0.05) larger based on both dry and wet weights although the dry weight/wet weight ratios were similar. Ventricular function curves were generated on each heart using an isolated working heart preparation. The isolated hearts of caffeine-fed rats exhibited a significant reduction in cardiac output, stroke volume, mean aortic pressure, and estimated myocardial work when compared to controls. The rats fed caffeine had greater plasma triglyceride levels with no significant differences in adipocyte size or number in the epididymal and perirenal depots. It is concluded that chronic caffeine intake from birth may alter cardiac function of the offspring.     

Inhibition of isotretinoin teratogenicity by acetylsalicylic acid pretreatment in mice.

Although isotretinoin (ITR) has been suggested to cause malformations via cytopathic effects on embryonic cells, the molecular mechanisms of ITR cytotoxicity in teratogenesis are not clear. Since ITR undergoes metabolism by prostaglandin synthase to a potentially cytotoxic peroxyl free radical, the possible role of prostaglandin synthase metabolism as a modulator of ITR teratogenicity was evaluated. Craniofacial and limb abnormalities were noted in fetuses on day 18.5 of gestation following administration of ITR to pregnant CD-1 mice in a three dose regimen of 100 mg/kg at 4 hr intervals on day 10.5 of gestation (plug day = day 0.5 of gestation). Mice were also treated with acetylsalicylic acid (ASA), an irreversible inhibitor of the cyclooxygenase component of prostaglandin synthase, at doses of 20 and 60 mg/kg body weight 2 hr prior to each ITR dose. ASA pretreatment of mice receiving ITR treatment showed a dose-dependent decrease in the overall incidence of malformations, number of defects per fetus, and the incidence of specific craniofacial and limb defects. Equivalent doses of ASA given to control mice did not cause malformations or alter the incidence of resorptions. These results demonstrate that ASA is able to ameliorate the teratogenic effects of ITR observed in fetal mice near term and indicate that prostaglandin metabolism could play a mechanistic role in ITR teratogenicity.     

Potentiating effect of caffeine on the teratogenicity of acetazolamide in C57BL/6J mice

Pregnant C57BL/6J mice were treated with 0 or 50 mg of caffeine (CAFF) per kg, and 0, 200 mg/kg (L) or 1,000 mg/kg (H) of acetazolamide (ACZM) during day 9 of gestation (9DPC). Individual fetuses were examined for gross morphological abnormalities and skeletal variations. The increase in fetal malformations seen, especially right forelimb electrodactyly, was augmented at both dose levels of acetazolamide by concomitant exposure to caffeine. Both frequency and severity of ectrodactyly were potentiated by caffeine. Skeletal examination revealed a reduction of the number of ossified cervical and caudal vertebral centra among litters exposed to ACZM at either dose. In either case (ACZM-H, ACZM-L) that effect was augmented by co-administration of CAFF. The first cervical vertebra (C1) appeared to provide the most sensitive index of teratogenic exposure. This study provides evidence that a subteratogenic dose of caffeine can potentiate the teratogenic effect of acetazolamide in C57BL/6J mice when dams are treated on day 9 of gestation. In addition, skeletal examination provided evidence that simultaneous treatment with both agents delayed fetal development. Many litters exposed to ACZM or both agents displayed a reduction in skeletal ossification even in the absence of gross morphological abnormalities, suggesting that ossification can be used as an indicator of prenatal exposure to potentially harmful substances in the C57BL/6 mouse strain.     

Phenytoin teratogenicity and midgestational pharmacokinetics in mice.

Mice of the A/J and C57BL/6J (C57) strains were dosed with phenytoin (PHT) every 48 hr throughout pregnancy by gastric intubation to test the hypothesis that maternal plasma PHT concentration may be the significant factor in determining PHT reproductive and developmental toxicity. Serial serum samples were obtained from each mouse from gestation day (GD) 10-GD 12 for determination of individual dam PHT pharmacokinetics. Maximum PHT concentration and PHT AUC (area under-the-time-concentration curve) were regressed to laparotomy and fetal evaluation endpoints to determine whether significant association existed. Although serum PHT concentrations exceeded levels associated with teratogenicity (greater than 10 micrograms/ml), few major malformations were induced in either strain. However, in the A/J strain, there was a significant increased incidence of hydrocephaly and open eyelid. Regression of pharmacokinetic parameters with embryo and maternal endpoints indicated significant associations between gestational weight gain and maximum concentration measured (Cmax) or AUC in both strains. This association was also found for fetal weight in the C57 strain. In the A/J strain, the induction of decreased ossification of the sternebrae was also associated with maternal PHT concentration; however, linear regression of hydrocephaly and open eyelid to PHT concentration was not statistically significant. These results suggest that maternal plasma PHT concentration may be a quantifiable determinant of certain aspects of PHT developmental toxicity in the mouse.     

The effect of prior exercise and caffeine ingestion on metabolic rate and hormones in young adult males

The purposes of this study were to examine (a) the effects of acute exercise on metabolic rate 24 and 48 h postexercise and (b) the interaction of acute exercise and the thermic effect of caffeine on metabolic rate and hormonal changes during the late postexercise recovery period. In six young males, who were regular consumers of caffeine, resting energy expenditure was measured before and after caffeine (5 mg.kg-1) and placebo ingestion under the following conditions: (i) control (e.g., no prior exercise), (ii) 24 h postexercise, and (iii) 48 h postexercise. Blood samples were drawn for plasma glucose, insulin, glycerol, free fatty acids, catecholamines, and thyroid hormones (triiodothyronine, thyroxine, and free thyroxine). Results showed that acute exercise did not exert a detectable effect on resting metabolic rate in the late postexercise recovery period, that is, resting metabolic rate was similar among the conditions of control (1.17 +/- 0.12 kcal.min-1), 24 h postexercise (1.16 +/- 0.12), and 48 h postexercise (1.16 +/- 0.11). Caffeine ingestion increased metabolic rate (approximately 7%), but the thermic effect was not different among the experimental conditions. Plasma insulin and norepinephrine were lower after caffeine ingestion, whereas an increase in plasma free fatty acids was noted. Other hormones and substrates did not change significantly in response to caffeine ingestion. Furthermore, the hormonal and substrate milieu was not significantly different 24 and 48 h postexercise when compared with the control condition. Our results support the view that acute exercise does not alter the resting metabolic rate in the late postexercise recovery period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Palate teratogenicity and embryotoxicity of cyclosporin A in mice.

Mice of the A/J and B10.A/SgSnJ strains were treated with 50 mg of cyclosporin A (CsA) per kg of body weight on day 12 of gestation. There were significantly more fetal resorptions in both the A/J and B10.A strain when treated with CsA than in controls treated with olive oil. A low frequency (7.6%) of isolated cleft palates were induced in the A/J strain, which was significantly greater than that observed in A/J mice treated with olive oil alone. No cleft palates were induced in B10.A, which suggests that any increase in susceptibility that was observed could not be attributed to H-2 linked genes.     

Meiosis suppression by caffeine in female mice

Summary The effects of caffeine on meiosis of mouse ova in vitro and in vivo have been studied. Concentrations of 200 g/cc or more suppressed entry of ova into in vitro meiosis without production of any numerical or structural abnormalities at dose levels above or below that. Acute superovulation by the standard technique was prevented at a dose of 0.25 mg/g/body weight and examination of the intrafollicular ova revealed presistence of the germinal vesicle stage. Chronic administration of the same dose (0.25 mg/g/bw) throughout the period from weaning to puberty did not induce any cytologically detectable meiotic abnormalities in ova studied in vitro at the end of that period. It is suggested that the reduced fertility seen by some previous authors may have been due to the suppression of entry into meiosis of the ova with diminished numbers of ova being ovulated.Aided by a grant from The National Foundation — March of Dimes.     

Exercise endurance 1, 3, and 6 h after caffeine ingestion in caffeine users and nonusers.

The purpose of the present study was to examine the duration of caffeine's ergogenic effect and whether it differs between users and nonusers of the drug. Twenty-one subjects (13 caffeine users and 8 nonusers) completed six randomized exercise rides to exhaustion at 80% of maximal oxygen consumption after ingesting either a placebo or 5 mg/kg of caffeine. Exercise to exhaustion was completed once per week at either 1, 3, or 6 h after placebo or drug ingestion. Exercise time to exhaustion differed between users and nonusers with the ergogenic effect being greater and lasting longer in nonusers. For the nonusers, exercise times 1, 3, and 6 h after caffeine ingestion were 32.7 +/- 8.4, 32.1 +/- 8.6, and 31.7 +/- 12.0 min, respectively, and these values were each significantly greater than the corresponding placebo values of 24.2 +/- 6.4, 25.8 +/- 9.0, and 23.2 +/- 7.1 min. For caffeine users, exercise times 1, 3, and 6 h after caffeine ingestion were 27.4 +/- 7.2, 28.1 +/- 7.8, and 24.5 +/- 7.6 min, respectively. Only exercise times 1 and 3 h after drug ingestion were significantly greater than the respective placebo trials of 23.3 +/- 6.5, 23.2 +/- 7.1, and 23.5 +/- 5.7 min. In conclusion, both the duration and magnitude of the ergogenic effect that followed a 5 mg/kg dose of caffeine were greater in the nonusers compared with the users.     

Lack of teratogenicity of aluminum hydroxide in mice

The embryotoxic and teratogenic potential of aluminum hydroxide, a therapeutic drug used as an antacid and phosphate binder, was investigated in Swiss mice. Mated female mice were given by gavage daily doses of 0, 66.5, 133 or 266 mg/kg of A1 (OH)3 on gestation days 6 through 15 and killed on gestation day 18. Females were evaluated for body weight gain, food consumption, appearance and behavior, survival rates, and reproduction data. No significant effects attributable to A1(OH)3 were noted in comparison of maternal body weight and food consumption values, appearance and behavior. No treatment-related changes were recorded in the number of total implants, resorptions, the number of live and dead fetuses, fetal size parameters or fetal sex distribution data. Gross external, soft tissue and skeletal examination of the A1-treated fetuses did not reveal differences at any dose in comparison with the controls. Thus, no evidence of maternal toxicity, embryo/fetal toxicity or teratogenicity was observed with A1(OH)3 in mice.     

Comparison of caffeine and theophylline ingestion: exercise metabolism and endurance.

This two-part investigation compared the ergogenic and metabolic effects of theophylline and caffeine. Initially (part A), the ergogenic potential of theophylline on endurance exercise was investigated. Eight men cycled at 80% maximum O(2) consumption to exhaustion 90 min after ingesting either placebo (dextrose), caffeine (6 mg/kg; Caff), or theophylline (4.5 mg/kg Theolair; Theo). There was a significant increase in time to exhaustion in both the Caff (41.2+/-4.8 min) and Theo (37.4+/-5.0 min) trials compared with placebo (32.6+/-3.4 min) (P<0.05). In part B, the effects of Theo on muscle metabolism were investigated and compared with Caff. Seven men cycled for 45 min at 70% maximum O(2) consumption (identical treatment protocol as in part A). Neither methylxanthines (MX) affected muscle glycogen utilization (P>0.05). Only Caff increased plasma epinephrine (P<0.05), but both MX increased blood glycerol levels (P<0.05). Muscle cAMP was increased (P<0.05) by both MX at 15 min and remained elevated at 45 min with Theo. This demonstrates that both MX are ergogenic and that this can be independent of muscle glycogen.     

Acute caffeine ingestion does not impair glucose tolerance in persons with tetraplegia.

Acute caffeine (Caf) ingestion impairs glucose tolerance in able-bodied humans during an oral glucose tolerance test (OGTT). The mechanism responsible for this effect remains unclear, however, it is suggested to be due to the accompanying increase in epinephrine concentration. We examined whether or not Caf would elicit a glucose intolerance in persons with tetraplegia (TP) who do not exhibit an increased epinephrine response following Caf ingestion. All TP [n = 14; 9 incomplete (Inc) lesion, 5 complete (Com) lesion] completed two OGTT 1 h after consuming either gelatin (Pl) or Caf capsules (dose = 4 mg/kg). Blood samples were collected at baseline (time = 0 min), 1 h after capsule ingestion (time = 60 min), and every 30 min during the OGTT (time = 90-180 min). Glucose, insulin, proinsulin, and C-peptide responses were similar (P > 0.05) between treatments, demonstrating no effect of Caf on glucose tolerance. This lack of a Caf effect may be due to the low epinephrine concentration that remained unchanged (P > 0.05) throughout all experiments. Interestingly, the Com exhibited a 50% higher glucose response (P 0.05) lower insulin response (vs. Inc), suggesting a more pronounced glucose intolerance within this subgroup. Furthermore, nine TP (5 Com, 4 Inc) had glucose levels of >or= 7.8 mM at the end of the OGTT (time = 180 min), classifying them as glucose intolerant. In summary, acute Caf ingestion does not increase epinephrine concentration or impair glucose tolerance in TP.     

Acute and habitual caffeine ingestion and metabolic responses to steady-state exercise.

This study compared the exercise catecholamine and metabolic responses to a caffeine challenge in trained subjects before and after a 6-wk period of increased caffeine ingestion. Trained subjects (n = 6) were challenged with 500 mg of caffeine followed by prolonged exercise before and after 6 wk of increased caffeine ingestion (500 mg ingested before each daily run). A control group (n = 6) of trained subjects followed the same protocol except for caffeine ingestion. Acute caffeine ingestion resulted in increased plasma epinephrine and decreased respiratory exchange ratio (RER) during exercise. After 6 wk of caffeine supplementation, the epinephrine response to exercise or caffeine plus exercise was decreased, although the latter still resulted in a lower RER value compared with exercise without caffeine ingestion. Activity of key metabolic enzymes (hexokinase, citrate synthase, phosphorylase, and 3-hydroxyacyl-coenzyme A dehydrogenase) from biopsies of the gastrocnemius showed no response to 6 wk of this increased adrenergic receptor stimulation and, on the basis of the lower RER, enhanced fat metabolism. This study suggests that caffeine ingestion by trained subjects causes increases in plasma epinephrine and reduces the RER during exercise. However, habitual stimulation results in a general dampening of the epinephrine response to caffeine or exercise. There was no indication that increased adrenergic stimulation and fat oxidation caused any adaptation in the activity of metabolic enzymes.     

Cytogenetic investigation of meiotic chromosomes of male mice after chronic caffeine treatment

Summary Male C3H inbred mice and male (101xC3H) F₁ hybrids were treated with various caffeine doses over a long period. After the end of treatment the animals were dissected and the metaphase I figures of the cycle of spermatogenesis were analysed. The experiments revealed no distinct evidence for the induction of chromosomal aberrations in the cycle of spermatogenesis caused by caffeine up to metaphase I.This study was supported by the Deutsche Forschungsgemeinschaft.