[Radioligand binding assay of progesterone receptors on normal fertile human sperm membrane].
OBJECTIVE
To investigate the progesterone-binding site on the normal fertile human sperm membrane after 2 hours of in vitro capacitation.


METHODS
Viable spermatozoa were selected by a swim-up method. After 2 hours of in vitro capacitation, multipoint saturation binding experiments were performed. Sperm suspension and increasing concentrations of progesterone-11alpha-glucuronide-[125I] iodotyramine (125I-P) were added to 7 total binding tubes respectively, and equal amounts of sperm suspension and 125I-P were added to another 7 corresponding non-specific binding tubes in the presence of 10 micromol/L progesterone. After incubation for 1 hour at 4 degrees C, the radioactivity of both the tubes and the pellets after centrifugation was measured respectively. The equilibrium dissociation constant (Kd) and maximum binding capacity (Bmax) were calculated using the mathematical model of single site multi-point saturation method of Scatchard function and least-squares regression.


RESULTS
Kd was (0.61 +/- 0.04) nmol/L and Bmax was (830 +/- 344) sites/cell. The significance test of the regression equation indicated that r = -0.980, P < 0.01.


CONCLUSIONS
There is a high affinity and low capacity binding site for the progesterone (progesterone receptor) on the normal fertile human sperm membrane.
Huo
Yong-wei
YW
Research Center of Reproductive Medicine, Xi'an Jiaotong University School of Medicine, Key Laboratory of Environment and Diseases-related Genes, Ministry of Education, Xi'an, Shaanxi 710061, China.
Qiu
Shu-dong
SD
Tian
Hong
H
Xu
Yong-jun
YJ
Wang
Li-rong
LR
Ge
Ling
L
D000328:Adult; D002462:Cell Membrane / Q000737:chemistry; D006801:Humans; D008297:Male; D011374:Progesterone; D011869:Radioligand Assay; D011980:Receptors, Progesterone / Q000032:analysis*; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000737:chemistry*
D011980:Receptors, Progesterone; D011374:Progesterone