Studies of hCG binding and endocytosis in rat ovary by ultrastructural immunocytochemistry

Abstract

Localization of hCG binding sites and the process of endocytosis in pseudopregnant rat ovaries were investigated by indirect electron-microscopic immunocytochemistry. Immature female rats were treated with pregnant-mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) to induce ovarian luteinization. Eight days after priming with PMSG-hCG and 1-6 h before sacrifice the animals were given another injection of hCG to bind the receptors. Receptor sites to hCG localized by reaction product were present in most luteal cells, but not in primary follicular cells. The receptor sites were distributed on luteal cell surfaces facing interstitial spaces. Endocytotic pits containing hCG binding sites were rarely seen 1 h after hCG injection. At 2h, hCG and presumably its receptor were taken up within endocytotic vesicles with the evidence of reaction product coated on the vesicle wall. With time, fusion of endocytotic vesicles with lysosome occurred and the reaction product appeared in phagolysosomes. The reaction product was localized on phagolysosomal inner surface or in free granular form. These findings suggest that hCG and its receptors were internalized through endocytotic pits and endocytotic vesicles and delivered to lysosomes probably for degradation. An additional experiment for localization of acid phosphatase was also performed to delineate the lysosomes and phagolysosomes.

Pathways of internalization of the hCG/LH receptor: immunoelectron microscopic studies in Leydig cells and transfected L-cells.

“…There have been several studies of the fate of hCG in target cells using either biochemical (5,6,14,15,45) or morphological (1,2,24,28,38) methods. However, no direct study of the LH receptor has been performed, at the electron microscopic level, probably due to the lack of specific antibodies.…”

Micropropagation and Acclimatization of Gymnocalycium cv. Fancy (Cactaceae): Developmental Responses to Different Explant Types and Hormone Conditions

“…The available information on in vitro propagation of Gymnocalycium is scarce and limited. Therefore, although relevant information exists for various species [42][43][44][45][46][47][48][49][50], more comprehensive research is needed to develop efficient and reproducible protocols for in vitro propagation. Additionally, these protocols should be feasible to implement and enhance performance in the ornamental plant industry.…”