Androgen binding to subcellular particles of rat testis.
Androgen binding activity was evaluated in different subcellular particulate fractions obtained by differential centrifugation of 32-day-old rat seminiferous tubules homogenates. After eliminating heavy particles by centrifugation at 4300 g during 4 min in 0.25 M sucrose buffer, a 27,000 g pellet was obtained and layered on 1.05 M sucrose buffer. The relatively light particulate interface (LPF) formed during centrifugation at 27,000 g 60 min, showed the highest androgen binding activity among particulate fractions. This binding was associated with the plasma membrane marker 5'-nucleotidase and it did not follow any of six other subcellular structure markers: DNA for nuclei, succinate dehydrogenase for mitochondria, acid phosphatase for lysosomes, NADPH-cytochrome C reductase for smooth endoplasmic reticulum, RNA for rough endoplasmic reticulum and lactate dehydrogenase for cytosol. In LPF, concentrations of sites were estimated to be 328 +/- 54 fmol per mg proteins and affinity constant 0.78 +/- 0.23 10(9) M-1. Heat stability, steroid specificity, affinity constant and rate of dissociation were similar to the well known androgen binding protein, ABP. Presence of ABP or a similar protein in subcellular particles might play a role in the mechanism of action of androgens in seminiferous tubules of maturing rats.
D000728:Androgens / Q000378:metabolism*; D000818:Animals; D002458:Cell Fractionation; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011944:Receptors, Androgen / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*; D012671:Seminiferous Tubules / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013737:Testis / Q000378:metabolism*; D014316:Tritium
D000728:Androgens; D011944:Receptors, Androgen; D011987:Receptors, Steroid; D014316:Tritium