Relaxin Content of Blood, Urine and Other Tissues of Pregnant and Postpartum Guinea Pigs.

Abstract

Relaxin appears in the blood serum of guinea pigs on about the 21st day of pregnancy which can be correlated with the first appearance of pubic relaxation as detected by palpation. The concn. of relaxin reaches a plateau of 0.5 G. P. units/ml. on the 28th day and is maintained until the 63d day, at which time the concn. falls to 0.33 G. P. units/ml. Immediately after parturition, a precipitous decline in the relaxin content of the blood serum is noted. The urine shows a concn. of 0.5 G. P. units by the 63d day. 10 G. P. units/g. of fresh tissue is found in the uterus on the 56th and 63rd day of pregnancy, whereas the placenta shows 5 G. P. units on the 56th day and 2.5 G. P. units on the 63d day. It is suggested that the drop in serum relaxin in the latter part of pregnancy may be due to a decreased output from the placenta.