The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings were not evaluated in accordance with the levels of evidence for reproductive or developmental criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of NTP or the U.S. Government.
Theophylline (THEOP), a natural component in tea that also finds pharmaceutical use as a bronchodilator, vasodilator, and a smooth muscle relaxant, was tested for its effects on reproduction and fertility in CD-1 mice using the RACB protocol. Data on food and water consumptions, body weights, and clinical signs during a two week dose-range-finding study (Task 1) were used to set exposure concentrations for the Task 2 continuous cohabitation study at 0.075, 0.15, and 0.3% w/v in feed. Feed consumption was not altered by THEOP addition. These levels gave calculated consumption estimates of nearly equal to 126, 260, and 500 mg THEOP/kg/day.
Alopecia occured in both sexes of all groups of treated animals (20-25% in the 0.075 group, and greater than 50% in the 0.15 and 0.3% groups). Seven mice died during Task 2: 3 controls, and 4 in the low dose group. A single control mouse showed alopecia; this was less severe than that seen in the treated mice.
Significant reproductive effects were observed: there was a 19% reduction in the mean number of litters per pair for the high dose mice, fewer live pups per litter at all doses (reduced by 22%, 29%, and 42% in the low - high dose groups, respectively), and, at the highest concentration level, a 6% decrease in live pup weight adjusted for litter size. The number of days to deliver each litter was consistently greater in the 0.3% THEOP group, being longer by 3 days for the first litter, and by 5 days for the last litter, and similarly increased for all others.
Given the significant effects on reproductive performance, a crossover mating was used in an attempt to identify the affected sex. In this mating trial, there were no differences in the percent of pairs mating, or delivering a live litter. However, in the group cohabiting control males and 0.3% exposed females, the proportion of pups born alive was reduced by 16%, and the adjusted live pup weight was reduced by 15%.
After the litters in Task 3 were delivered, evaluated, and discarded, the females were evaluated for vaginal cyclicity for 7 days, and then the F0 mice in the control and 0.3% theophylline groups were killed and necropsied. There was a 5% increase in female terminal body weights in the 0.3% THEOP group, and an 11% increase in liver weight adjusted for body weight. Interestingly, there were no changes in the length of the estrous cycle, or in the percent of time spent in the various estrous stages. Treated male terminal body weights were reduced by 7% vs. controls. Body-weight-adjusted seminal vesicle weight decreased by 19%. Epididymal sperm density was reduced by 20% in the high dose group; the % motile and the percent of abnormal morphologic forms were unchanged by 0.3% THEOP exposure.
No second generation analysis was conducted.
In summary, theophylline, at these levels of intake, caused significant adverse reproductive effects (fewer live pups/litter, with reduced pup weight and fewer litters/pair at the high dose, as well as reduced seminal vesicle weight and epididymal sperm number) in the absence of changes in parental body weight. Although alopecia may be taken as evidence of "general toxicity", it is unlikely to "cause" the reproductive effects in the same way that, for example, hepatic or renal toxicity may adversely impact reproductive capability. Still unaddressed by this study is the possibility that early exposure may adversely influence the development of the reproductive system, as modeled in rodents.