OBSERVATIONS ON THE HISTAMINOLYTIC ACTIVITY OF DOG THORACIC DUCT LYMPH

¹ Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois

The histaminolytic activity of dog thoracic duct lymph is considered to be the result, at least in part, of its diamine oxidase content.

An in vitro method for the quantitative determination of this histamine inactivating principle, based upon the biological assay of residual histamine and upon the kinetics of the lymph-histamine reaction, is described. The mean initial lymph DO activity of eleven control dogs was found to be 1.81 ± 0.539 microgm. histamine inactivated/ml. lymph/hour.

A spontaneous and precipitous fall in blood pressure is accompanied by a marked but transient increase in the DO activity of thoracic duct lymph of dogs, whether expressed in terms of concentration or in terms of absolute amount per unit time. Lymph DO activity was observed to be moderately increased during acute bilateral adrenalectomy, but in only one dog out of seven was there a further increase following completion of the operation. Three chronically adrenalectomized dogs displayed only a negligible lymph DO activity. The administration of cortisone or adrenal cortex extract to four normal and two chronically adrenalectomized animals produced no significant change in lymph histaininolytic activity. Natural epinephrine HCl in large doses produced a moderate but significant increase in normal dogs. The significance of these findings is discussed.