THE POTENCY OF BLOOD SERUM OF MARES IN PROGRESSIVE STAGES OF PREGNANCY IN EFFECTING THE SEXUAL MATURITY OF THE IMMATURE RAT

Abstract

The blood of 62 mares was tested for its potency in inducing sexual maturity of immature rats. Serum from non-pregnant mares was negative in all instances as was the serum of mares up to the 37th day of pregnancy. The time of pregnancy at which the serum first gave a positive reaction varied in different individuals from the 37th to the 42nd day. Between the 43rd and 80th day of pregnancy the serum had the most marked effect upon the size of the ovaries of the test animals. At this time medium doses produced marked enlargement and extensive histological alterations of the ovaries of the experimental animals. At later stages of pregnancy the reactions to the injections of the serum were confined to changes in the uterus and vagina. A correlation was observed to exist between the period of high concentration of anterior hypophyseal hormone in the serum and the time of implantation in the mare. The authors were able with the same sample of serum given in varying doses to demonstrate a quantitative relationship between the amount injected and the reaction manifested in the ovary at definite stages of pregnancy. The presence of the anterior hypophyseal sex maturing hormone in the blood of pregnant mares may be used as a means of diagnosing pregnancy of 6-7 weeks'' duration in these animals. This reaction continues until about the 100th day of pregnancy. Later reactions are characterized by changes in the uterus and vagina only and are probably elicited by folliculin. Tests were not made beyond the 222nd day of pregnancy.