Abstract
I. The presence of 0.16M magnesium chloride in the incubation mixture for the Gomori method for localizing alkaline phosphatase activity, markedly increases the enzyme activity in the nuclei of the guinea pig endometrium, ovary and adrenal cortex, rendering them visible after 5 minutes' incubation. The activity in cytoplasmic and extracellular sites is decreased. The staining of these same nuclei could be demonstrated by the Loveless and Danielli method of visualizing the phenolic component of a complex phosphate ester instead of precipitating the phosphate ions with calcium salts. The activity described may be specific for the tissues mentioned and serves as an instance in which nuclear staining in phosphatase preparations is clearly valid.
II. The effect of magnesium and cyanide ions and other factors on the enzyme activity noted histochemically in nuclei and biochemically in nuclear cell fractions, was reviewed. The data support the validity of some earlier histochemical observations describing a nuclear phosphomonoesterase activity in many organs which differs from that in cytoplasmic and extracellular sites. They also suggest that the phosphatase activity in cell fractions of those biochemical preparations prepared in aqueous media are altered by diffusion and adsorption phenomena.