Effect of nickel(II)acetate on distribution of calmodulin in the rat kidney

The effect of subcutaneous injection of a single dose of nickel(II)acetate (95 mumol/kg body wt.) on the distribution of calmodulin in the membrane and cytosolic fractions of kidneys of F344/NCr rats was studied with the use of radioimmunoassay. Over the first 8 h post-injection, the membrane-bound calmodulin concentration increased by 20% versus the control value of 3.84 +/- 0.54 SE micrograms/g wet tissue. That increase was then followed by a gradual decrease to the control value in 7 d. At the same time intervals, the cytosolic calmodulin concentration first decreased by 13% from the control value of 8.81 +/- 2.1 SE micrograms/g wet tissue and then slowly increased, reaching a level of 12% above the control at day 7 post-injection. Statistical analysis of the results after 8 h revealed a downward trend in the membrane-bound (P less than 0.0014) and upward trend in the cytosolic (P less than 0.0207) calmodulin concentrations until day 7. However, the total renal calmodulin calculated from the membrane/cytosolic distribution data did not show any statistically significant treatment-related differences among the mean values (13.39 micrograms/g for the nickel(II)acetate-treated rats vs. 12.56 micrograms/g wet tissue for the controls between days 1 and 7). Therefore, the observed effect of nickel(II)acetate must be attributed only to temporary transfer of calmodulin from the soluble cytosolic form into an insoluble, membrane-bound form, without any detectable influence on its degradation or synthesis rate.