Analysis of ovarian structure and radioimmunoassay analyses of estradiol and progesterone: control versus tetrapeptide (TPAL)-treated hamsters.

The contraceptive tetrapeptide produced by Calbiochem, San Diego, Calif. (TPAL-CBC) was used to demonstrate that its primary effect is to prevent maturation of ovarian follicles. Other parameters (the presence of corpora lutea, ova in the oviducts, or embryos postcoitum, and levels of plasma estradiol and progesterone) are dependent on the initial observation of nonmaturation of ovarian follicles.