Selenium, cadmium, zinc, and copper in human kidney cortices and post mortem indices of hypertension

Abstract

Kidneys from 32 autopsied Caucasian human subjects aged 16-60 were frozen then lyophilized while the flasks were kept in insulating containers. (Subjects with evidence of extensive weight loss, chronic renal failure, or carcinoma were not included). Replicate samples of cortex were removed, weighed, and wet-ashed in HNO3-HClO4. Zn, Cd, and Cu were estimated by atomic absorption spectrophotometry with the 2261 Å line used for Cd background correction. Se was estimated by fluorescence with DAN in a Turner fluorimeter, but a #74 Kodak Wratten filter was added to minimize the 500 nm interference noted by E. Pickett (personal communication, 1980).Means and variability for the three elements in kidney cortex were similar to those in a North Carolina study as was Cd/(Cd+Zn)×100. Cortical Cd (P<0.05), Zn (P<0.10), and Cd/(Se·Zn) (P<0.05) increased with age, whereas Se showed no significant relationship with age. Age(2), nonlinear effects of age, had a slight influence upon Cu (P<0.05) only if data were not adjusted for gender. There was no influence of ageper se upon Cu with or without adjustment for gender. The scatter diagrams of element concentrations plotted vs age contained several provocative "outlier" values.A positive association of kidney cortex Cd concentration, or Cd/(Se ·Zn), with postmortem indices of hypertension existed only if age, gender, and age(2) were omitted from the multiple regression equation. This adjustment was not included in a similar study of North Carolina cases and appears to be the source of the major difference in their respective inferences drawn about the positive relationship of kidney cortex Cd with evidence of hypertension. This difference in statistical models does not however account for the failure of the West Virginia sample to indicate a protective role of kidney cortex Se suggested for the North Carolina subjects. Larger samples, drawn from regions differing in Se abundance, will be necessary to test the latter question adequately.