Influence of Sex and Thyroid Principles on the Antiproteolytic Activity of Rat Serum

Abstract

SummaryExamination of antiproteolytic activity in rats administered sex steroids and thyroid principles revealed the following :Female rats display lower serum antitrypsin and antiplasmin activity than their male counterpart under all conditions investigated. In long-term experiments, antiplasmin values of castrated females returned to preoperative levels while male titers remained below the preoperative values. Testosterone pro-prionate administration to intact female rats produced significant elevation of antitrypsin and antiplasmin titers whereas estradiol benzoate was largely ineffective in producing any major change in antiproteolytic activity.Surgical or medical thyroidectomy (propylthiouracil) initially produced a marked depression of antiplasmin activity followed by a restoration of preoperative levels. Administration of thyroxine or triiodothyronine to intact or hypothyroid rats led to a further decrease in titer which persisted throughout the course of study. It would appear that acute alteration in metabolic state, regardless of direction, may initiate a reduction in net antiplasmin activity.