Gonadotropin stimulation of cyclic adenosine monophosphate and testosterone production without detectable high-affinity binding sites in purified Leydig cells from rat testis

Journal Article · Fri Feb 01 00:00:00 EST 1991 · Steroids; (USA)

DOI:https://doi.org/10.1016/0039-128X(91)90129-J· OSTI ID:5642841

Browne, E S; Bhalla, V K ^[1]

---

1. Medical College of Georgia, Augusta (USA)

Rat testicular interstitial cells were separated by three different gradient-density procedures and, with each, two biochemically and morphologically distinct cell fractions were isolated. The lighter density cells in fraction-I bound iodine 125-labeled human chorionic gonadotropin (hCG) with high-affinity (apparent equilibrium dissociation constant, Kd, approximately 10{sup {minus} 10} M) without producing either cyclic adenosine monophosphate or testosterone in response to hormone action. The heavier-density cells displayed morphologic features typical of Leydig cells and produced cyclic adenosine monophosphate and testosterone in the presence of hCG without detectable {sup 125}I-labeled hCG high-affinity binding. These cell fractions were further characterized by studies using deglycosylated hCG, a known antagonist to hCG action. Cell concentration-dependent studies with purified Leydig cells revealed that maximal testosterone production was achieved when lower cell concentrations (0.5 x 10(6) cells/250 microliters) were used for in vitro hCG stimulation assays. Under these conditions, the {sup 125}I-labeled hCG binding was barely detectable (2.24 fmol; 2,698 sites/cell). Furthermore, these studies revealed that the hCG-specific binding in Leydig cells is overestimated by the classic method for nonspecific binding correction using excess unlabeled hormone. An alternate method is presented.

• OSTI ID: 5642841
• Journal Information: Steroids; (USA), Vol. 56:2; ISSN 0039-128X
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
AMP
BIOSYNTHESIS
GONADOTROPINS
BIOCHEMICAL REACTION KINETICS
TESTOSTERONE
AFFINITY
ANIMAL CELLS
DOSE-RESPONSE RELATIONSHIPS
IODINE 125
MAN
RATS
RECEPTORS
TESTES
TRACER TECHNIQUES
ULTRACENTRIFUGATION
ANDROGENS
ANDROSTANES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CENTRIFUGATION
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
GONADS
HORMONES
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KETONES
KINETICS
MALE GENITALS
MAMMALS
MEMBRANE PROTEINS
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PITUITARY HORMONES
PRIMATES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RODENTS
SEPARATION PROCESSES
STEROID HORMONES
STEROIDS
SYNTHESIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques