SERUM VASOCONSTRICTOR (SEROTONIN)

Abstract

In the first paper of this series (1) the partial purification of a vasoconstrictor substance from beef serum was reported. Further purification of the active substance led to its isolation. A preliminary report of the method together with analytical and pharmacological data has also been published (2). It is the purpose of this paper to present the details of the method of isolation, the more complete analyses now at hand, and some further characterizations of the substance. The problem of isolating this principle presented the difficulties usually encountered in vitamin research (3) in that the substance was present in the source material (beef serum) in a dry weight concentration of about 0.005 per cent. Initial obstacles were overcome with the preparation of a stable concentrate which was 0.8 per cent pure and contained 25 to 35 per cent of the activity originally present in the serum (the percentages are calculated from the activity of the pure substance). This concentrate was composed mainly of the ammonium salt of 5-nitrobarbituric acid (the precipitating agent). The active principle appeared to be involved in this concentrate in some kind of complex, since repeated recrystallization did not effect important changes in activity of the crystals so obtained. After many procedures which resulted in large losses of activity were tried, it was found possible to separate 90 per cent of the inactive materials from the concentrate with a loss of less than 5 per cent of the total activity by precipitating them with acetone from hot aqueous solution. Concentration of the filtrate and recrystallization of the residue from methyl alcohol led to the isolation of a crystalline substance with vasoconstrictor action in the rabbit ear preparation approximately twice that of commercial epinephrine.