During a two year experiment, local
sarcomas developed in 5 of 20 rats injected intramuscularly (i.m.) with 120 mumol of
nickel(II)hydroxide air-dried gel (DRY), in 3 of 20 rats similarly injected with 120 mumol of crystalline industrial
nickel(II)hydroxide (CRST) and in 16 of 20 rats injected i.m. with 40 mumol of
nickel subsulfide (Ni3S2). I.m.
injections of 120 mumol of freshly precipitated colloidal
nickel(II)hydroxide (COL) did not produce
tumors. No
tumors were found in animals which had been injected i.m. with 15 doses of 4.4 mumol of
nickel(II)
sulfate (NiSO4) (total dose equalled 66 mumol/rat) or
sodium sulfate (Na2SO4; controls). Statistical analysis ranked the
tumor yields as follows: Ni3S2 greater than CRST = DRY greater than COL = NiSO4. The in vitro solubilization rates of the
hydroxides and
nickel subsulfide in human blood serum, artificial lung fluid and
ammonium acetate buffer, pH 7.4, were found to increase in the following order: Ni3S2 less than CRST less than DRY less than COL. Hence, an inverse relation may exist between the
tumor yield and rate of solubilization of the compounds tested.