GONADOTROPIN AND PROSTAGLANDINS BINDING-SITES IN NUCLEI OF BOVINE CORPORA-LUTEA

Highly purified nuclei isolated from bovine corpora lutea showed marked enrichment of NAD pyrophosphorylase, a marker for this organelle. Rough endoplasmic reticulum and lysosomal markers were undetectable, whereas plasma membrane and Golgi markers were detectable but not enriched in nuclei. These highly purified nuclei exhibited specific binding with 125I-labeled human choriogonadotropin, [3H]prostaglandin E1 and [3H]prostaglandin F2α. However, these bindings were only 15.4% (human choriogonadotropin), 7.9% (prostaglandin E1) and 8.9% (prostaglandin F2α) of the plasma membrane binding observed under the same conditions. Washing of nuclei and plasma membranes twice with buffer containing 0.1% Triton X-100 resulted in gonadotropin and prostaglandin F2α binding site and 5′-nucleotidase (EC 3.1.3.5) losses from nuclei that were different from those observed for plasma membranes. More importantly, the washed nuclei exhibited 44% (human choriogonadotropin), 21-26% (prostaglandins) of original specific binding despite virtual disappearance of 5′-nucleotidase activity. The nuclear membranes isolated from nuclei, specifically bound 125I-labeled human choriogonadotropin and [3H]prostaglandin F2α to the same extent or significantly more ([3H]prostaglandin E1, P < 0.05) than nuclei themselves, despite the marked losses of chromatin. In summary, our data suggest that gonadotropin and prostaglandins bind to nuclei and that this binding was intrinsic and was primarily associated with the nuclear membrane. © 1979.