Acidum Nucleicum. Nucleic Acid.
Synonyms.—Nucleinic Acid; Nuclein.
Nucleic acid, as used in medicine, is prepared from yeast. It consists chiefly of the true nucleic acid of yeast, with a proportion of albuminate (metaprotein) and carbohydrate. Other nucleic acids are known, notably those prepared from spleen pulp, from thymus gland substance, from salmon milt, and from pancreatic tissue. They are organic acids of unknown constitution which yield, as dissociation products, phosphoric acid, pyrimidine and purine derivatives; amongst the latter, hypoxanthine, xanthine, adenine, and guanine. If yeast, spermatozoa, or pus cells be extracted with acids a residue is obtained which has been termed nuclein. This residue is acid and contains a considerable amount of phosphorus. If it be further treated with alkalies or is subjected to tryptic digestion the protein is split off, the nucleic acid which remains containing all the phosphorus. The acid occurs as a greyish-white powder. It is gradually decomposed on boiling with dilute acids, or even by heating with water, but is resistant towards the action of alkalies, especially if sodium or potassium acetate be present. It is acid to litmus, will decompose carbonates, and forms salts with metals. The nucleic acids are amorphous bodies, and their alkaline solutions form precipitates with salts and mineral acids. The term "nuclein" is commonly used as a synonym of nucleic acid, but it is more correctly applied to the albumin nucleinates intermediate between nucleic acid and nucleo-protein.
Insoluble in alcohol and ether; very slightly soluble in water and dilute acids, soluble in dilute alkalies and in potassium acetate solution.
Action and Uses.—Nucleic acid is credited with some power to neutralise toxins present in the blood. It produces in tuberculosis a reaction similar to tuberculin. Nucleic acid is administered internally in pills and cachets; solutions of its sodium salt (5 per cent.) are used orally and by hypodermic injection. Given by injection, it increases the number of white blood corpuscles. This effect is preceded by a hypoleucocytosis lasting some three or four hours, the leucocytes then leave their normal situations and come out in rapidly increasing numbers into the free circulation. It has been suggested, but on no definite evidence, that they may act as an indirect bactericide in tuberculosis, endocarditis, septicaemia and other bacterial infections. Nucleic acid is also given to heal chronic and varicose ulcers. A hydrolytic product of nuclein is known as thymic or thyminic acid, and is also supplied under the trade-name Solurol. It is a brownish-yellow, slightly deliquescent, amorphous powder, practically without taste, with a feebly acid reaction, and soluble in water. It is given in powders, compressed tablets, or cachets, and is best taken with or immediately following a meal. Thyminic acid is a uric acid solvent, capable of holding in solution practically its own weight of uric acid at 20°, and one and a half times its weight at blood temperature (37°); on this evidence it has been prescribed in gout. Solutions of the acid are said to have no incompatibles. The dose of thyminic acid is from 2 ½ to 4 ½ decigrams (4 to 7 grains). In addition to the sodium compound, nucleinates of iron, silver, mercury and copper are prepared. Compounds of iron with nuclein are known under the trade-names Fer Ascoli and Nucleogen, the latter containing arsenic.
Dose.—Of powder, 6 to 30 centigrams (1 to 5 grains); of 5 per cent. solution of sodium salt, by the mouth, 4 to 8 mils (1 to 2 fluid drachms); by hypodermic injection, 1 mil (15 minims).