The effects of neuraminidase and gangliosides on ovarian LH/hCG receptors during rat development.
Ovaries of neonatal rats are not endowed with specific LH/hCG receptors up to 6-8 days of age. Treatment of ovarian membranes of the neonatal rat with neuraminidase results in a specific binding of radioactively labeled hCG, while an increase of hormone binding is observed after neuraminidase treatment of ovarian membranes of the 21-day-old rat. These changes in hormone receptor sites in the ovary are dependent on the neuraminidase concentration used and are due to a receptor with a dissociation constant (KD) of about 10(-9) M. The KD of the receptor in the LH/hCG sensitive ovary without neuraminidase treatment is about 10(-10) M. These results indicate the presence of two different LH/hCG receptors in the ovarian membrane. The unmasking effect of neuraminidase onto LH/hCG receptors indicate that ganglioside-like structures are responsible for the masking of receptors in the neonatal, insensitive rat ovary and also in the 21-day-old sensitive ovary. Ganglioside preparations are able to inhibit the binding, and the fractionation of ovary gangliosides results in a fraction with a rather high inhibition potency of LH/hCG binding to the receptor. It is hypothesized that the masked receptor in the sensitive period represent a store of receptors for the reconstitution of the ovarian cells with active receptors after internalization of the hormone-receptor complex. Thus the masking of the receptors in the early postnatal rat ovary could be a prerequisite for the female differentiation of hypothalamic centers. The observed neuraminidase effect in vitro could reflect a physiologic situation. Neuraminidase was found in the ovary, and during early postnatal development the neuraminidase activity pattern coincides with that of the ovarian LH/hCG receptor changes.
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000378:metabolism; D005260:Female; D005732:Gangliosides / Q000494:pharmacology*; D008297:Male; D009439:Neuraminidase / Q000378:metabolism / Q000494:pharmacology*; D010053:Ovary / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011974:Receptors, LH; D013737:Testis / Q000201:enzymology
D006063:Chorionic Gonadotropin; D005732:Gangliosides; D011956:Receptors, Cell Surface; D011974:Receptors, LH; D009439:Neuraminidase