Binding and internalization in vivo of (/sup 125/I)hCG in Leydig cells of the rat
The present study was performed to demonstrate the binding, mode of uptake, pathway and fate of iodinated human chorionic gonadotropin ((/sup 125/I)hCG) by Leydig cells in vivo using electron microscope radioautography. Following a single injection of (/sup 125/I)hCG into the interstitial space of the testis, the animals were fixed by perfusion with glutaraldehyde at 20 minutes, 1, 3, 6 and 24 hours. The electron microscope radioautographs demonstrated a prominent and qualitatively similar binding of the labeled hCG on the microvillar processes of the Leydig cells at 20 minutes, 1, 3, and 6 hours. The specificity of the (/sup 125/I)hCG binding was determined by injecting a 100-fold excess of unlabeled hormone concurrently with the labeled hormone. Under these conditions, the surface, including the microvillar processes of Leydig cells, was virtually unlabeled, indicating that the binding was specific and receptor-mediated. In animals injected with labeled hCG and sacrificed 20 minutes later, silver grains were also seen overlying the limiting membrane of large, uncoated surface invaginations and large subsurface vacuoles with an electron-lucent content referred to as endosomes. A radioautographic reaction was also seen within multivesicular bodies with a pale stained matrix. At 1 hour, silver grains appeared over dense multivesicular bodies and occasionally over secondary lysosomes, in addition to the structures mentioned above, while at 3 and 6 hours, an increasing number of secondary lysosomes became labeled. At 24 hours, binding of (/sup 125/I)hCG to the microvillar processes of Leydig cells persisted but was diminished, although a few endosomes, multivesicular bodies and secondary lysosomes still showed a radioautographic reaction. No membranous tubules that were seen in close proximity to, or in continuity with, endosomes and multivesicular bodies were observed to be labeled at any time interval.
- Research Organization:
- McGill Univ., Montreal (Canada)
- OSTI ID:
- 5175848
- Journal Information:
- J. Androl.; (United States), Vol. 9:1
- Country of Publication:
- United States
- Language:
- English
Similar Records
Different processing of LH/hCG receptors in cultured rat luteal cells and murine Leydig tumor cells (MLTC-1)
Subcellular distribution of ( sup 3 H)-dexamethasone mesylate binding sites in Leydig cells using electron microscope radioautography
Related Subjects
GONADOTROPINS
AUTORADIOGRAPHY
BIOCHEMICAL REACTION KINETICS
ANIMAL CELLS
BIOLOGICAL PATHWAYS
CELL MEMBRANES
CYTOPLASM
IN VIVO
IODINE 125
LYSOSOMES
RATS
SPECIFICITY
TESTES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GONADS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
KINETICS
MALE GENITALS
MAMMALS
MEMBRANES
NUCLEI
ODD-EVEN NUCLEI
ORGANOIDS
ORGANS
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOISOTOPES
REACTION KINETICS
RODENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques