Introduction and objective:
Caffeine is a natural methylxanthine widespread throughout the food industry. Many research studies have shown that caffeine readily crosses the placenta causing teratogenic and embryotoxic effects. The objective of this study was to assess the influence of caffeine, administered at 10°C, on the development of a rat’s bone tissue, with particular reference to elemental bone composition using an X-ray microprobe.

Material and Methods:
The research was conducted on white rats of the Wistar strain. The fertilized females were divided into two groups: an Experimental Group (Group E) and a Control Group (Group C). The females in Group E were given caffeine orally (at 10°C) in 30 mg/day doses from the 8^th – 21^st day of pregnancy. The females in Group C were given water at the same temperature. The foetuses were used to assess the growth and mineralization of the skeleton. Qualitative analysis of the morphology and mineralization of bones was conducted using the alcian-alizarin method. For calcium and potassium analysis, an X-ray microprobe was used.

Results:
By staining the skeleton using the alcian-alizarin method, changes in 47 Group E foetuses were observed. The frequency of the development variants in the Group E rats was statistically higher, compared with Group C.

Conclusions:
On the basis of these results, it can be concluded that caffeine in high doses disturbs the development of bone tissue. An additional factor which enhances the adverse effects of this substance on bone tissue is the temperature of the administered solution (10°C). In the Experimental Group, a significant decrease in the calcium level, as well as an increase in the potassium level, was observed. The X-ray microprobe can be a perfect complement to the methods which enable determination of the mineralization of osseous tissue.