Comparison of cellular distribution of LH receptors and steroidogenic enzymes in the porcine ovary

Abstract

Previous studies have shown a heterogeneous expression of LH receptors in various structures of the porcine ovary. Specially striking was the existence in the preovulatory follicle of inner layers of theca interna cells devoid of LH receptor and the confinement in the corpus luteum of the LH receptor to the external cellular layers. In the present study, we have compared the steroidogenic capabilities of LH receptor-positive and -negative cells using immunocytochemistry for side-chain cleavage P450, 3 beta-hydroxysteroid-dehydrogenase, 17 alpha-hydroxylase P450 and aromatase P450. We have also examined, using the same methods, the evolution of the various cell types after ovulation and during the development of the corpus luteum. In preovulatory follicles the inner layers of theca cells which were not labelled with anti-LH receptor antibodies appeared to express the steroidogenic enzymes in a way similar to that of the outer LH receptor-positive cell layers. Ovulation per se did not change the distribution of LH receptors (present in the outer luteal cells and in the granulosa) or of steroidogenic enzymes. However, 48 h after follicular rupture there as a marked decrease in overall labelling with anti-LH receptor antibody, and especially a disappearance of immunostaining in the luteal cells of granulosa origin. In the mid-luteal phase (6 days after ovulation), the receptor content seemed to increase in the peripheral luteal cells derived from the theca but the receptor did not reappear in the granulosa-derived luteal cells. Thus the down-regulation of LH receptor appeared to be reversible in the external thecal layers but irreversible in the granulosa cells. Furthermore, the distribution of the various steroidogenic enzymes in the corpora lutea delineated granulosa-derived from theca-derived cells and showed that only the external layers of the latter expressed the LH receptor. These results showed the existence in the preovulatory follicle of two theca interna regions expressing the same steroidogenic enzymes but possibly submitted to a different hormonal control. Furthermore, the cells derived from these two regions as well as the cells of granulosa origin showed a distinct pattern of variation of LH receptivity during the development of the corpus luteum. During these studies we also observed that, in the interstitial tissue, only a minority of cells which derived from remnants of atretic follicles expressed both the LH receptor and the steroidogenic enzymes.

Endocrine Effects of GnRH Agonist Application to Early Pregnant Gilts

“…The absence of high LH pulses in our study may argue that a temporal increase in LH may not be sufficient to increase P4 levels. Furthermore, the existence of two theca interna regions expressing the same steroidogenic enzymes but submitting to different hormone controls has been demonstrated [24]. These two regions and the cells of granulosa origin revealed distinct patterns of LH receptivity during CL development.…”

Basolateral Localization and Transcytosis of Gonadotropin and Thyrotropin Receptors Expressed in Madin-Darby Canine Kidney Cells

“…This suggested that the corresponding targeting signals are embodied in the proteins themselves and are functional in heterologous polarized cells. Furthermore, the basolateral localization of the LH receptor in MDCK cells, a receptor which is not physiologically polarized (22,23), suggested that the LHR also possessed a basolateral targeting signal as the other members of this receptor subgroup. In vitro mutagenesis will allow us to identify the signals involved in all three receptors.…”

“…LH receptor-driven hormone transcytosis was observed through endothelial cells of testicular blood vessels (19). Recently immunocytochemistry using specific monoclonal antibodies demonstrated the basolateral distribution of the TSH receptor in thyroid cells (20) and of the FSH receptor in Sertoli cells (21), whereas the LH receptor was present all over the cell surface of thecal, granulosa, and luteal cells in the ovary and Leydig cells in the testes (22,23).The question was thus raised as to whether these differences in cellular distribution were due to differences in the structure of receptors or simply secondary to the fact that thyroid follicular cells and Sertoli cells are polarized, whereas the LH receptor-expressing cells are not polarized. Another question raised was whether the mechanisms of receptor basolateral delivery were cell-specific or whether the receptors contained specific signals that could direct them to this membrane compartment in any polarized cell.…”

“…LH receptor-driven hormone transcytosis was observed through endothelial cells of testicular blood vessels (19). Recently immunocytochemistry using specific monoclonal antibodies demonstrated the basolateral distribution of the TSH receptor in thyroid cells (20) and of the FSH receptor in Sertoli cells (21), whereas the LH receptor was present all over the cell surface of thecal, granulosa, and luteal cells in the ovary and Leydig cells in the testes (22,23).…”

Effects of luteinizing hormone and follicle stimulating hormone on the developmental competence of porcine preantral follicle oocytes grown in vitro

“…LH receptors are expressed on theca cells from preantral and antral follicles, and on granulosa cells from large antral follicles [15][16][17][18]. LH may play multiple roles throughout follicular development, but most studies have focused on the action in late-stage follicles and during the periovulatory period.…”