End Of Incubation Period Research Articles

Metabolism of 14C-antipyrine in suspensions of isolated rat liver cells.

Suspensions of liver cells isolated from perfused rat livers were incubated with antipyrine-N-methyl-14C. Antipyrine was eliminated by first-order kinetics during incubations for 3 hours with primary suspensions (parenchymal cells + non-parenchymal cells) and suspensions of purified parenchymal cells. Antipyrine concentrations were unchanged when incubated with suspensions of non-parenchymal cells, dead cells or medium only. At the end of incubation period, 4-OH-antipyrine and 3-CH2OH-antipyrine were detected mainly as the glucuronide or sulphate conjugates, and evidence for the N-demethylation of antipyrine was also obtained. Half-lives for elimination of antipyrine in primary cell suspensions were not significantly different from the half-lives measured in parenchymal cell suspensions. This finding together with the lack of metabolism of antipyrine found in non-parenchymal cell suspensions suggest that oxidation and conjugation of antipyrine is mainly confined to the parenchymal cells. There was significant inhibition of antipyrine metabolism in primary suspensions by phenylbutazone (1.6 X 10(-3)M), dexamethasone (2 X 10(-4)M) and ethanol (1.3 X 10(-2)M, 0.75%). We suggest that the use of primary suspensions of isolated rat liver cells provide a rapid and simple method for the study of factors influencing drug metabolism in the liver.

EFFECT OF MIXING VARYING QUANTITIES OF DICYANDIAMIDE WITH AMMONIUM FERTILIZERS ON NITRIFICATION OF AMMONIA IN SOILS

A series of laboratory experiments were conducted to evaluate the effect of dicyandiamide on the transformation of fertilizer nitrogen in Georgia soils. These studies indicated that dicyandiamide inhibited nitrification of ammonium sulphate at all rates utilized. The inhibitory action of dicyandiamide was attributed to its toxic effect on the nitrifying organisms which failed to function in the presence of dicyandiamide. Complete nitrification eventually occurred but only after a long period.Decomposition of dicyandiamide was more rapid in fine-textured Cecil sandy loam containing relatively more organic matter than on the coarse-textured and low organic matter Lakeland sandy soil. Soil texture and organic matter content are two factors that must be considered in evaluating the length of time that dicyandiamide will inhibit nitrification in any given soil.Sucrose apparently provided a quickly available source of energy for soil microorganisms that utilized the dicyandiamide as a source of nitrogen and preventing its inhibiting effect on nitrification. The nitrogen from the dicyandiamide was eventually mineralized as indicated by the higher total ammonium and nitrate nitrogen found at the end of incubation period.