Vasodilator constituents of tissue extracts

IN a previous communication [Best, Dale, Dudley and Thorpe, 1927] we were able to prove that the chief vasodilator constituent of both ox liver and lung was histamine (/3-iminazolylethylamine) by the isolation of this substance in a state of chemical purity from alcoholic extracts of each organ under con- ditions which precluded its formation by autolysis or bacterial action during the process of isolation.Now since extracts of almost all organs of the body have been shown to provide depressor substances, it would be of considerable physiological im- portance if more definite information as to the chemical nature of these could be obtained; for until our own investigations began no depressor substance other than choline had been isolated under conditions which are absolutely free from suspicion of contamination by bacterial action.The important work of Abel and Kubota in this connection has been considered in the paper quoted above.With a view to selecting the most suitable organ for examination it became necessary to review the distribution of the depressor substances; for although this field has been explored by a number of workers their extracts have been both prepared and tested by different methods.To collect such data and use them as a comparative survey of the distribution of the vasodilators would in all probability be very misleading.Thus it seemed that reliable information could only be obtained by preparing and estimating the activity of the extracts under standardised conditions.For this purpose the alcohol method of extraction already described [Best, Dale, Dudley and Thorpe, 1927] seemed preferable since, while absolute sterility was ensured, this method would be least likely to permit of any hydrolytic changes taking place.Extracts from a number. of organs of horse and ox have been prepared by the alcohol method and the extracts thus obtained, after removal of alcohol and fat, were tested on the blood-pressure of the cat in comparison with pure histamine.Except in the case of spleen no attempt has been made to deter- mine the influence of choline on the histamine-like activity.Since the values