9 1991 by The Humana Press, Inc. All rights of any nature, whatsoever, reserved. 0163-4984/91/2901-0035 $02.00

Distribution of Structural and Trace Elements in Human Temporal Bone VLADIMIR KATI(~, ~ GORAN VUJICIC, 5 DAVOR IVANKOVI(~,4 ANA STAVLJENI(~, *'3 AND SLOBODAN VUKICEVI(~ 2

'Clinics of Otorhinolaryngoiogy; 2Department of Anatomy; qnstitute of Clinical Laboratory Diagnostics; 4Department of Statistics, Zagreb University School o f Medicine; and ~Department of Analytical Chemistry, School of Science, University of Zagreb, Zagreb, Yugoslavia Received April 2, 1990; Accepted April 30, 1990

ABSTRACT This study was undertaken to evaluate a systematic analysis of mineral and trace elements of individual functionally determined parts of adult temporal bone. Marked differences were observed in basic structural elements (Ca, P, Mg, and Zn) among different bone regions. The more so, molar Ca/P ratio was significantly different in various regions, being highest in the hammer and vestibular regions. Taxonomic analysis revealed specific differences in the mineral ratio between the two petrous bone regions believed to develop from various embryonal bases. According to results, the observed differences in mineral trace element composition of particular regions of human temporal bone might be explained by their developmental specificifies and functional adaptation. Key Words: Temporal bone; petrous bone; trace elements; ICPAES.

INTRODUCTION T e m p o r a l b o n e is a complex b o n e system, its constituents u n d e r g o ing various d e v e l o p m e n t a l courses to a d a p t t h e m to different a n d specialized functions. Anatomical location of the temporal bone, a n d role of *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research

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sense organs located in it appear to suggest the existence of various forces acting on the bony labyrinth and the pyramid-surrounding structures. These forces may induce both static and dynamic deformations of the temporal bone. Osseous tissue of the temporal bone is actively and functionally adapted to static and dynamic loading acting on it. This adjustment is manifested as a change in bone densitynprimarily in the content of minerals, and in the concentration and composition of elements taking part in the mineral segment construction. Few quantitative studies on the element composition of particular functionally and anatomically defined temporal bone sections have been published so far. The related studies have mostly been focused on the analysis of differences in the contents of calcium and phosphorus in the stirrup, and cortical bone of the cochlea in otosclerosis, because this material is much easier to obtain during surgical procedures (1-4). Systematic analyses of individual functionally determined parts of the temporal bone in adults concerning their contents of minerals and trace elements are, however, still lacking. This paper reports on the results of an extensive investigation of the levels of calcium, magnesium, phosphorus, zinc, strontium, copper, and iron in adult human petrous bone. MATERIAL AND M E T H O D S Temporal bones were obtained by autopsy from 27 subjects who had not suffered from any disease that might have influenced the bone mineral content. Subjects' age ranged between 36 and 77 yr. Immediately after autopsy, the bones were frozen at - 70~ and stored until preparation of temporal bone specimens. Each temporal bone was closely examined using an operating microscope, and the following regions were isolated: area vestibularis inferior (AVI), area vestibularis utriculoampullaris (AVU-A), basis stapedis (BS), cellula mastoidea (CM), crura et capitum stapedis (CS), canalis semicircularis inferior (CSI), foramen stylomastoideum (FS), incus (I), malleus (M), modiolus (MO), promontorium (P), and tractus spiralis foraminosus (TSF). After isolation, samples were first deffated for 72 h (alcohol:ether, 1:1) in quartz flasks and then lyophilized for 24 h. Nitric acid (HNO3, Suprapun, Merck, FRG) was then added in single drops until all organic material was destroyed. After cooling, the solution was transferred to 25 mL Erlenmeyer flasks and diluted with deionized water until the appropriate volume was reached (5). The content of minerals (Ca, P, Mg, and Zn) and trace elements (Fe, Cu, and Sr) was analyzed by inductively coupled plasma emission spectrometry (ICP-AES) on an ARL 35000 C spectrometer (Bausch & Lomb, ARL, USA). Statistical analysis was done by the standard and multivariate analyses (6). Biological Trace Element Research

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Elements in Human Temporal Bone Table 1 Distribution of Structural Minerals and Essential Trace Elements in Human Petrous Bone (U/rag dry wt) Element Ca (~g/mg) P (p~g/mg) Mg (p~g/mg) Zn (ng/mg) Sr (ng/mg) Cu (ng/mg) Fe (ng/mg)

n 174 174 174 174 174 77 77

~ 266.7 114.6 2.72 265.8 67.5 20.5 105.6

SD 23.4 10.1 0.18 15.4 6.8 9.2 16.3

CV (%) 8.7 8.8 6.9 5.8 10.1 44.6 15.4

RESULTS Table 1 shows m e a n values of minerals and trace elements in all examined specimens from 12 temporal bone regions. The content of calcium and p h o s p h o r u s in the temporal bone was found to be 266.7 p~g/ mg and 114.6 p,g/mg, respectively. Other minerals were present in considerably lower concentrations, whereas Sr, Cu, and Fe were found in ng a m o u n t s only. These results were lower than those obtained by neutron activation (7). Marked differences were observed, however, a m o n g the basic structural element contents, in particular, bone regions (Table 2). Namely, highest concentrations of Ca were found in the superior vestibular region (AVU-A) and perforated spiral tractus (TSF), and lowest in the h a m m e r (M) and stylomastoid opening (FS). Highest concentrations of phosphorus w e r e observed in the limbs and head of the stirrup (CS), whereas they w e r e lowest in stylomastoid opening (FS). According to the order of concentrations, calcium was almost without exception followed by phosphorus in the temporal bone regions u n d e r study (Table 3), with correlation of 0.987. In all the 12 regions studied, the m e a n concentration of m a g n e s i u m was 2.716 + 0.186 p~g/mg, and was lower in comparison with other adult h u m a n bones. The highest concentration of magnesium, h o w e v e r , was observed in the superior vestibular region (2.913 +_ 0.112 ~g/mg), and the lowest in the area of stylomastoid opening (2.536 + 0.121 p~g/mg). The concentration of m a g n e s i u m was found to positively correlate with the contents of calcium and p h o s p h o r u s (Table 3). Small a m o u n t s of strontium w e r e detected in the temporal bone. Highest concentrations w e r e present in the h a m m e r (0.07262 _ 0.004 p~g/ mg) and lowest in the stirrup plate (0.06117 + 0.003 p,g/mg). The content of strontium was found to positively correlate with the Concentration of m a g n e s i u m (Table 3), but not with the contents of calcium and phosphorus. Biological Trace Element Research

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