Effect of intrauterine injection of casein on fetal survival in rat: a new pharmacological approach for contraception.
BACKGROUND
The incidental finding of casein as a possible new local pharmacological contraceptive prompted us to assess its validity in an experimental rat model.


METHODS
The intrauterine injection of 150 microg of bovine alpha-casein dissolved in 150 microL phosphate-buffered saline (PBS) was performed on one uterine rat horn on days L(5)-L(7), whereas the contralateral horn was used for injection of 150 microL PBS as a control. Intraperitoneal injection of alpha-casein (5 mg/mL, 2 mL/rat) was performed on day L(5). The rats were killed by cervical dislocation on the day L(14).


RESULTS
The effect of an alpha-casein on fetal resorption rate was assessed following the unilateral injection of 150 microL of alpha-casein (1 mg/mL in PBS) and compared with the effect obtained following the contralateral injection of 150 microL PBS. The unilateral injection of alpha-casein on day L(5) caused a significant increase in fetal resorption rate as compared with the contralateral uterine horn injected with PBS (p<.00001). The decrease in alpha-casein concentration from 1 to 0.3 mg/mL caused a reduced, but still significant, effect on fetal resorption rate (p<.0001). The injection on days L(6)-L(7) caused a local effect of resorption near the injection site. There was no effect on fetal resorption rate following the injection of alpha-casein intraperitoneally.


CONCLUSIONS
Our data suggest a new pharmacological approach for contraception, based on local intrauterine effect of alpha-casein in an experimental rat model. The exact mechanism of action related to casein should be further studied.
Halperin
Reuvit
R
Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin 70300, Israel. ruvith@asaf.health.gov.il
Shinnar
Nili
N
Kronfeld-Schor
Noga
N
Hadas
Eran
E
D000818:Animals; D002364:Caseins / Q000008:administration & dosage / Q000494:pharmacology*; D002417:Cattle; D003267:Contraception / Q000379:methods; D005260:Female; D005327:Fetal Resorption / Q000139:chemically induced*; D007274:Injections, Intraperitoneal; D011247:Pregnancy; D051381:Rats; D014599:Uterus
D002364:Caseins