Characterisation of receptors for 1,25-dihydroxyvitamin D3 in the human testis.
Specific high affinity receptors for 1,25-dihydroxyvitamin D3 have been demonstrated in the human testes. The mean binding affinity (Kd +/- SD) of the receptor for 1,25-dihydroxyvitamin D3 was 1.75 +/- 0.32 x 10(-10) M but the binding capacity was low (mean Nmax +/- SD = 0.53 +/- 0.18 fmol/mg protein). Binding was time- and temperature-dependent, with a maximum binding achieved after 1 h at 25 degrees C. Although binding also took place at 4 and 37 degrees C, higher and more rapid binding was found at 25 degrees C. Furthermore, the binding between the ligand and the receptor was specific since only unlabelled 1,25-dihydroxyvitamin D3 competed with the labelled ligand. Binding of 1,25-dihydroxyvitamin D3 was abolished by trypsin and heat. Sucrose density gradient centrifugation revealed a sedimentation coefficient of 3.6S.
Habib
F K
FK
University Department of Surgery, Western General Hospital, Edinburgh, Scotland.
Maddy
S Q
SQ
Gelly
K J
KJ
D001667:Binding, Competitive; D002117:Calcitriol / Q000378:metabolism*; D006801:Humans; D008297:Male; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000032:analysis*; D013379:Substrate Specificity; D013696:Temperature; D013737:Testis / Q000032:analysis*
D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D002117:Calcitriol