Experimental Acceleration of Secretion of Urine in Fetal Rats. ∗

Abstract

In the fetal rat, ligation of the ureter causes the development of hydroureter and hydronephrosis, while ligation of the urogenital papilla causes the storing of urine † in the bladder. 1 The rate of secretion of urine, especially during the last 2 days of gestation, is much more rapid than studies in certain mammals suggest. 2

The present account deals with attempts to speed up the rate of secretion by introducing urea into the fetal circulation and by causing metabolites to accumulate in the maternal circulation (ligation of renal pedicles of mother). Using a method recently described 3 and ether for anesthetizing the mother, each fetus except those in Groups A and H (Table I) was transferred to the abdominal cavity of the mother. The outlet of the bladder was blocked by ligating the urogenital papilla. The fetuses in Group J were subjected to laparotomy before ligating the papilla; by means of micro-pipette prepared for the purpose, the bladder was punctured and the urine already present was removed. After completing the several steps, the abdominal incision of the mother was closed (by suturing) and ether was discontinued. Subsequently, exactly 2 hours after tying off the papilla, each fetus was secured by severing the umbilical cord and killed by decapitation (decapitated at about the 16th hour before expected parturition or, in other words, at the end of the 21st day after observation of coitus). The bladder was dissected, removed from the body and weighed before and after removing the urine.

The data show that when a highly concentrated solution of urea was injected under the fetal skin the rate of secretion was accelerated (Group E). Although this is of interest in that it demonstrates the ability of the fetal kidney to secrete urine more rapidly than normally, the changes in osmosis thus produced suggest that the urea did not act solely as a specific diuretic agent. This view is supported by the data obtained from GroupsF and G.