BioFactors 30 (2007) 243–248 243 IOS Press Role of endogenous zinc in bones of newborn rats Z. Drzazga a,∗ , K. Michalik a , K. Maciejewska a , H. Trzeciak b and M. Kaszuba c a A. Chelkowski Institute of Physics, Department of Medical Physics, University of Silesia, Katowice, Poland b Department of Prosthetic Dentistry, Medical University of Silesia, Bytom, Poland c Institute of Stomatology, Katowice, Poland Abstract. Concentration of abundant elements e.g. calcium as well as of elements present in trace amount e.g. zinc in mandibles of 7, 14 an 28 day old newborn rats were determined by X-ray fluorescence analysis. The measurements were carried out by using a measurement system containing X-ray tube ECLIPSE-III and X-ray and gamma ray detector XR-100T-CdTe (Amptek Inc.). Concentration of calcium and zinc depended on the region of interest on the rat’s mandible due to mineralization degree conditioned by its function. Increasing age produced a remarkable increase in Ca content in contrast to Zn content in the bone tissue obtained from 7, 14 and 28 day old newborn rats. The calculated Zn/Ca concentration ratio was the biggest for 7 day old newborns and successively decreased with age indicating the important role of zinc at the beginning of bone ontogenesis. Keywords: Calcium, mandible, ontogenesis, X-ray fluorescence, zinc 1. Introduction The hardness and rigidity of bones depends on incorporation of the mineral into protein matrix containing crystals of hydroxyapatite. Calcium, phosphorus, magnesium and zinc (Ca, P, Mg and Zn) are the primary bone-forming minerals. This paper is focused on the role of Ca and Zn in bone development. It is known that Ca is responsible for the stimulation of bone formation and the inhibition of bone resorption [1] Crystallization of bone salt occurs in several stages, proceeding from amorphous calcium phosphate through intermediate crystalline structures, such as octocalcium phosphate [9]. Zinc plays a physiologically important role in bone tissues especially in the regulation of bone metabolism and bone protein synthesis [10]. Its supplementation could have beneficial effects on bone density [5]. In contrast to Ca the role of Zn as a bone growth factor in growing animals and humans has not been fully explained [6,7]. Several techniques have been used in trace elements analysis of bones, e.g. atomic absorption spectrophotometry, neutron activation analysis, X-ray microanalysis [2–4,6]. X-ray fluorescence (XRF) is a useful non-destructive analytical technique to study the concentration of various elements in bone, blood, head hair as well as kidney stones. The present study was undertaken to determine the role of endogenous calcium and zinc in bone mineralization of newborn rats with age by means X-ray fluorescence. * Address for correspondence: Professor Z. Drzazga, A. Chelkowski Institute of Physics, Department of Medical Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice, Poland. E-mail: drzazga@us.edu.pl. 0951-6433/07/$17.00  2007 – IUBMB/IOS Press and the authors. All rights reserved