Table 2.—Effect of added Mg**on NAD reductase activity with and 
without added @-glycerophosphate. E dilution factor is 10x. Sam- 
ple is pool of three control livers of cunners, Tautogolabrus adsper- 
sus. 
NAD reductase activity 
(A A*°X10%/min/0.10 ml E) 
Final concen without added with @-GP 
Mg**(mM) substrate (10 mM final conc) 
0 5 41 
2 29 48 
20 65 75 
vertebrates), but the assay protocol here was designed 
to reduce that variable as much as possible, by using 
the enzyme activity without added magnesium as a 
base from which to measure magnesium activation. 
Table 3 lists data showing a mild cadmium effect 
upon the magnesium activation of cunner liver 
NADR: in fish exposed for 96 hr to 24 ppm Cd, an ap- 
proximately 10-fold increase in magnesium concen- 
tration (20 mM) is required to activate NADR as 
much as 2 mM Mg does in the control fish. 
In frozen-stored cunner skeletal muscle, what 
appeared to be a significant difference in ME proper- 
ties of pooled fish exposed to cadmium, as contrasted 
with pooled controls, must be ascribed to individual 
variation. @GPdH activity was very high, but there 
was no apparent difference in properties between the 
cadmium-exposed and the control fish. 
Electrophoretic studies are as yet inconclusive. 
Despite considerable variation in the total-protein 
pattern, there is an area of tentatively labeled metal- 
protein complexes that appeared in most cases (8 
series out of 10) to increase in fish that had been ex- 
posed to cadmium (Fig. 1); many more data would be 
necessary to establish statistical validity, however, 
and individual variation renders this approach 
questionable in an acute-static study. Detoxification 
mechanisms of this nature may be more prominent in 
a chronic study. 
Of the serum enzymes tested for isoenzyme varia- 
tion, only a-naphthyl butyrate esterase activity 
produced a difference in pattern between cadmium- 
exposed and control fish; but here again, individual 
variation was very strong. 
On the whole, the observations made in the course 
of this preliminary experimentation seem to point to 
further work with metal-activated enzymes and with 
the stress-indicator transaminases. The most clear- 
cut effects were obtained by using assays designed to 
measure the degree of ligand activation or inhibition. 
LITERATURE CITED 
AMADOR, E., and W. E. C. WACKER. 
1965. Enzymatic methods used for diagnosis. In D. Glick 
(editor), Methods of biochemical analysis, Vol. 13, p. 265-356. 
Interscience Publ., N.Y. 
ANONYMOUS. 
1972. ‘“‘Itai-itai byd’”’ and other views on cadmium,. Food 
Cosmet. Toxicol. 10:249-255. 
BERGMEYER, H.-U., and E. BERNT. 
1963. Glutamate-oxaloacetate transaminase. In H.-U. Berg- 
meyer (editor), Methods of enzymatic analysis, p. 837-845. 
Academic Press, N.Y. 
CALABRESE, A., R. S. COLLIER, and J. E. MILLER. 
1974. Physiological response of the cunner, Tautogolabrus 
adspersus, to cadmium. I. Introduction and experimental 
Table 3.—Mg-dependent NAD reductase activity in liver of cunner, Tautogolabrus adspersus, 
exposed for 96 hr to 24 ppm Cd, 25 ppt salinity. Each value is the average of two tests, and each sam- 
ple is a pool of three livers. 
Increase in activity (A A**°X10*/min) 
effected by addition of Mg** to assay medium 
0 ppm Cd 
24 ppm Cd 
final concen Mg**+(mM) 
Homogenate 
final concen MG*+(mM) 
dilution 
factor 0 (Init. A A) 2 20 0 (Init. A A) 2 20 
10x 0 (5) 24 60 0 (13) 1 35 
10X 0 (9) 29 54 0 (22) 0 26 
5X 0 (21) 10 83 0 (23) 4 32 
5x 0 (22) 35 56 0 (18) 12 27 
2X 0 (23) 26 57 - - 
5x ) (18) 20 88 = 
5X 0 (20) 24 dl - = = 
5x 0 (2) 10 45 
