Distribution of insulin binding sites on Leydig cells of rat testes using insulin-coated gold particles.
The distribution of insulin binding sites in Leydig cells dispersed with collagenase from rat testes was studied using insulin-coated gold particles as an electron opaque ligand. Using electron microscope is convenient to distinguish Leydig cells among a variety of cells in crude preparations by their ultrastructural characteristics. Leydig cells were shown to possess insulin-binding sites on their plasma membranes. Initial binding sites of insulin were located to the microvillous surfaces. Following binding, receptor-ligand complexes seemed to move to the intermicrovillous plasma membrane, then to be internalized. Two modes of the internalization were confirmed. Most of the receptor-ligand complexes on Leydig cells appeared to be internalized via large, uncoated plasma membrane invaginations, while the remainder became internalized via small pits into vesicles. The receptor-ligand complexes were subsequently transferred to large subsurface vacuoles with electron-lucent lumens believed to correspond to endosomes. The reason why IGCs on the postendosomal pathway moving toward lysosomes was also discussed.
Kimura
M
M
Department of Anatomy, Aichi Medical University, Japan.
Lukinius
A
A
Ericsson
J L
JL
Grimelius
L
L
D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism*; D007985:Leydig Cells / Q000502:physiology / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains
D007328:Insulin