Abstract
Roussy, Oberling and Guerin 1 have reported that thorium dioxide is carcinogenic when administered intraperitoneally to rats. Doerr 2 and Hara 3 report that thorium and some of the associated periodic members agglutinate bacteria, red blood cells, spores, and precipitate proteins. The effects produced upon enzymes by carcinogenic substances, especially arsenites and hydrocarbons, have been rather extensively investigated. Recently Sure et al. 4 found marked reduction in the blood serum amylase, blood serum esterase and in the trypsin of tumour bearing albino rats. Pancreatic amylase and blood serum phosphatase were only slightly decreased according to their findings. The present communication reports the results of a series of experiments upon the effects of thorium, zirconium and titanium which are members of Group IV-A of the Periodic System, and cerium, which is a Rare Earth metal but which shows many physiological properties in common with these others, upon amylase, invertase, phosphatase and trypsin activity. The salts employed wrere thorium nitrate, Th(NO3)4; cerium nitrate, Ce(NO3)3 · 6 H2O; zirconium nitrate, Zr(NO3)4; and titanous chloride, TiCl3, which was allowed to oxidize and must be considered as tetravalent titanium.
Amylase activity was determined by estimating the amount of maltose liberated from a one per cent starch solution by a purified bacterial amylase (B. mesentericus) (Kindly supplied by the Wallerstein Laboratories, N. Y.) by the iodine titration method of Willstatter-Schudel. 5 A veronal buffer 6 at pH 6.8 was employed. Inorganic phosphate buffers were avoided since the phosphates of the rare metals are very insoluble. Twenty-five cc. of one per cent starch solution, 10 cc. veronal buffer, 2.0 cc. of 10-2 M rare metal salt were brought to 60°C. and 1.0 cc. of enzyme solution containing 2.0 × 10-2 mg. solid per cc. was added.
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