High abundance androgen receptor in goldfish brain: characteristics and seasonal changes
Testosterone (T) exerts its actions in brain directly via androgen receptors or, after aromatization to estradiol, via estrogen receptors. Brain aromatase activity in teleost fish is 100-1000 times greater than in mammals and would be expected to significantly reduce the quantity of androgen available for receptor binding. Experiments were carried out on the goldfish Carassius auratus to determine if androgen receptors are present in teleost brain and whether their physicochemical properties reflect elevated aromatase. Cytosolic and nuclear extracts were assayed with the use of (/sup 3/H)T and charcoal, Sephadex LH-20, or DNA-cellulose chromatography to separate bound and free steroids. Binding activity was saturable and had an equally high affinity for T and 5 alpha-dihydrotestosterone. Although mibolerone was a relatively weak competitor, the putative teleost androgen 11-ketotestosterone, methyltrienolone (R1881), estradiol, progesterone, and cortisol were poor ligands. Characteristics that distinguish this receptor from a steroid-binding protein in goldfish serum are the presence of binding activity in both nuclear and cytosolic extracts, a low rate of ligand-receptor dissociation, electrophoretic mobility, sedimentation properties in low vs. high salt, and tissue distribution. DNA cellulose-adhering and nonadhering forms were detected, but these did not differ in other variables measured. Although goldfish androgen receptors resembled those of mammals in all important physicochemical characteristics, they were unusually abundant compared to levels in rat brain, but comparable to levels in prostate and other male sex hormone target organs. Moreover, there were seasonal variations in total receptors, with a peak at spawning (April) 4- to 5-fold higher than values in reproductively inactive fish.
- Research Organization:
- Boston Univ., MA (USA)
- OSTI ID:
- 6838490
- Journal Information:
- Endocrinology; (United States), Vol. 123:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANDROGENS
RECEPTORS
ISOMERASES
ENZYME ACTIVITY
BIOCHEMICAL REACTION KINETICS
BRAIN
CELLULOSE
CENTRIFUGATION
CHEMICAL PROPERTIES
CHROMATOGRAPHY
DNA
GOLDFISH
PHYSICAL PROPERTIES
SEASONAL VARIATIONS
TESTOSTERONE
TISSUE DISTRIBUTION
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANDROSTANES
ANIMALS
AQUATIC ORGANISMS
BODY
CARBOHYDRATES
CENTRAL NERVOUS SYSTEM
DISTRIBUTION
ENZYMES
FISHES
HORMONES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KETONES
KINETICS
LABELLED COMPOUNDS
MEMBRANE PROTEINS
NERVOUS SYSTEM
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
PROTEINS
REACTION KINETICS
SACCHARIDES
SEPARATION PROCESSES
STEROID HORMONES
STEROIDS
VARIATIONS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques