Abstract
It has been shown 1 that in rabbits the daily injection of aspartic acid and guanidine produces a definite rise in blood pressure. The blood proteins of these animals were analyzed both before and after a definite and prolonged elevation of the blood pressure was obtained. Control animals injected with putrescin, tyrosine, and tryptophane were observed for a similar length of time and their blood proteins were analyzed.
The red cells were separated from the oxalated blood by hypertonic sodium sulphate as suggested by Folin 2 , and the protein precipitated from the supernatant fluid with sulphuric acid. This procedure precipitates all the serum proteins from a definite volume of blood. The Van Slyke 3 method of protein analysis was adapted to micro methods.
The whole blood, the red cells, and the serum proteins from I cc. of blood were hydrolyzed with 10 cc, of concentrated HCl in a small Erlenmeyer flask covered with a funnel and placed on a sand bath. The hydrolysis was continued for 4 hours and the mixture evaporated to dryness on the water bath. The contents of the flask were diluted to 15 cc, transferred to a large centrifuge tube and magnesium hydroxide added, then aerated for 1 hour for the determination of the amide nitrogen. The residue is centrifuged, filtered, and washed, and the filtrate and washings diluted to 40 cc. Five cc. is removed for the determination of nitrogen after hydrolysis, and to the remaining filtrate, 5 cc. of 10% phosphotungstic acid in 10% H2SO4 is added, the mixture allowed to stand overnight, then centrifuged and washed with phosphotungstic acid solution. The entire precipitate obtained by centrifugation was digested and the total nitrogen determined, which gives basic amino nitrogen precipitated by phosphotungstic acid.
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