Among soft tissue organs which store fluoride (F-), the aorta contains the highest levels. [1-2]. Calcifications of arteries of the Monckeberg type have been reported in relatively young persons afflicted with skeletal fluorosis from endemic areas. [3-5] It was, therefore, of interest to determine whether or not there is a systematic correlation of F- levels with those of calcium (Ca++) in the aorta.
Methods. Aorta tissues were selected at random from 23 autopsies, without reference to sex, age or cause of death, on persons who died in 3 Detroit hospitals  of various diseases. In 16 cases F- and Ca++ determinations were made on grossly calcified tissue and compared with those
in adjacent tissue which showed no gross evidence of calcification. In 7 additional cases only F- levels were determined in both grossly calcified and less calcified tissue.
The tissues were collected in plastic containers with an alkaline F–free formalin solution. From each aorta specimen all grossly calcified pieces were separated and placed together, as were pieces of the less calcified areas. Both sets of samples were finely chopped until they were homogeneous.
F- was separated by the double distillation method of WILLARD and WINTER  and titrated by the WILLIAMS  procedure as modified by SMITH and GARDNER . Two determinations were made on each sample.  For the Ca++ determination, another weighed portion of the same samples was ashed in platinum crucibles at 575? for 16 h. The ash was then taken up in the minimum quantity of 0.1 M HC1 and the Ca++ separated from orthophosphate and heavy metals through the use of gelatinous hydrolysis product of Zr4.+  The Ca ++ was then determined by a complexometric titration with EDTA with calcon as the indicator. [12,13]
Results. Ca ++ levels: In all instances, the grossly calcified tissues contained moderately more Ca++ than the less calcified tissue, except in case 8, a 49-year-old woman with a brain tumor (Table I). Here the Ca ++ levels of both specimens were relatively low and about equal, namely 2.4 and 2.8 mg/g (2400 and 2800 ppm). The highest Ca ++ level in the calcified group was 161 mg/g in case 2, the lowest 2.3 mg/g in case 15.
F- levels: Fluoride content of the aorta varied widely from person to person. In 4 out of the ‘less calcified’ tissues, the F- levels were nil. Only one (case 13), of the ‘grossly calcified’ specimens showed a F- level of 0. Here the Ca++ content was 14.2 mg/g. The highest F- content of 165 ppm was encountered in a ‘grossly calcified’ specimen (case 3).
Ca++/F- ratio: The Ca++/F – mole ratio varied non-systematically from 11-1820 between the ‘grossly calcified’ and the ‘less calcified’ tissues. There was no consistent proportion of Ca ++ to F- in either group of aorta samples.
Additional data. Aorta/bone fluoride ratio: Bones are known to store more F- than other tissues. A possible correlation between aorta F- and bone F- was explored by evaluating statistically the detailed data from another study. In 1960, CALL et al.  for F- analyzed 60 aortas
(Table II). Their F- levels showed a remarkably wide range, from 0.3 in a 69-year-old person to 258 ppm in an 80-year-old person, with a mean of 30.0 ppm. The F- content of dry fat-free bones ranged from 40 ppm to 2025 ppm with a mean of 557 ppm. Bone Ca ++ levels were more consistent. They ranged from 14.0-29.5%. Statistical evaluation of these data detected no correlation between aorta F- and bone F. 
Age and F-: In the present study, as well as in that of CALL et al. , there was a strong numerical correlation between age and aorta F-.
Aorta F- and disease : CALL et al.  noted a significantly higher storage of bone F- in cases with pyelonephritis, but no relationship of aorta F- levels with the causes of death. In the present study, no correlation could be established between aorta F- levels and the disease.
Discussion. As indicated in Table I, F- levels in the aorta depend little, if at all, on the amount of Ca++ present. That F- does not seem to be bound in appreciable amounts as calcium-fluoride (CaF2), has been recognized by others, with respect to bones and teeth.  The erratic
fluctuations of F- levels in the aorta from person to person are noteworthy in this as well as in CALL’s study. Some samples of aorta tissue contained virtually no F-, and others up to 258 ppm. In a single organ such as the placenta  or in the skin of patients with various dermatological lesions  F- levels vary widely in closely adjoining tissue areas.
Since the F- content of the aorta does not parallel F- levels in the skeleton, bone F- cannot be considered a criterion of F-‘s presence elsewhere in the system nor can possible ill effects in the system be precluded on the basis of low F- levels in bones.
1. F. A. SMITH, D. E. GARDNER, N. C. LEONE, and H. C. HODGE, Am. Med. Ass. Arch. Ind. Hlth. 21, 330 (1960).
2. R. A. CALL and D. A. GREENWOOD, Progress Report on the Effect of Atmospheric Fluorides in Man, Grant S.83, Sept. 1, 1957-Aug. 31, 1958, Div. Research Grants, N.I.H., U.S. Dept. Health, Education and Welfare; R. A. CALL, D. A. GREENWOOD, W.H. LECHEMINANT, J. L. SHUPE, H. M. NIELSEN, L. E. OLSON, R. E. LAMBORN, F. G. MANGELSON, and R. V. DAVIS, Publ. Hlth. Rep., Wash. 80, 529 (1965).
3. S. P. KUMAR and R. A. KEMP HARPER, Dr. J. Radiol. 36, 467 (1963).
4. G. NALBONE and F. PARLATO, Folia med. 40, 81 (1956).
5. S. CHAWLA, K. KANWAR, O. P. BAGGA, and D. ANAND, J. Ass. Physns India 72, 221 (1964).
6. Case 16 was obtained through the courtesy of Dr. J. B. BACON of Ames, Iowa, and reported by him in J. Am. med. Ass. 181, 933 (1964).
7. H. H. WILLARD and O. B. WINTER, Ind. Engng Chem. analyt. Edn. 5, 7 (1933).
8. H. A. WILLIAMS, Analyst 71, 175 (1946).
9. F. A. SMITH and D. E. GARDNER, J. dent. Res. 30, 182 (1951).
10. Analyses were made by GEORGE KOSEL, Passaic General Hospital, Passaic, New Jersey.
11. M. D. DERDERIAN, Analyt. Chem. 33, 1796 (1961).
12. C. L. YARBRO and R. L. COLBY, Analyt. Chem. 30, 504 (1958).
13. G. P. HILDEBRAND and C. N. REILLEY, Analyt. Chem. 29, 258 (1957).
14. The statistical work was performed on the basis of the 1958 N.I.H. Research Report prior to the appearance of the published paper in Public Health Report 80, 529 (1965), by J. M. LvcAs and Prof. L. J. SAVAGE of the Department of Statistics at Yale University.
15. S. M. WEIDMANN, J. A. WEATHERALL, and R. G. WHITEHEAD, J. Path. Bact. 78, 435 (1959).
16. R. FELTMAN and G. KOSEL, Science 122, 560 (1955).
17. G. L. WALDBOTT, J. Asthma Res. 2, 51 (1964).
18. I appreciate the cooperation of Drs. E. BOOTH and J. R. MCDONALD, pathologists at Hutzel and Harper Hospitals respectively, for furnishing the aorta specimens; D. L. J. SAVAGE and Mr. J. M. Lucas of the Department of Statistics at Yale University for their statistical interpretation of my data; Dr. R. A. KEMP HARPER, St. Bartholomew’s Hospital, London, England, and Dr. G. NAL-
BONE, Department of Industrial Medicine, University of Palermo, Italy, for furnishing the illustrations in Figures 1 and 2.