Baboon corpus luteum: presence of oxytocin receptors.
To determine whether the effect of oxytocin (OT) on progesterone production in primate luteal tissue may be receptor-mediated, we used biochemical procedures to examine the CL of the baboon (Papio anubis) for the presence of OT receptors (OT-R). CL (n = 5) were obtained by luteectomy from the early (LH + 1-5 days), mid- (LH + 6-10 days), and late (LH + 10-15 days) luteal phases. Biopsies from the uterine fundus were also obtained at the same time. Total receptors were measured by incubating the membrane fractions (120,000 x g fraction) with increasing concentrations of [3H]oxytocin (0.08-1.6 nM) for 30 min at 22 degrees C with a protein concentration of 200 micrograms per tube. Nonspecific binding was evaluated by the addition of excess nonradioactive OT. The receptor-bound tritiated ligand was separated from the nonreceptor-bound ligand through use of polyethylene glycol. For the midluteal phase CL, the affinity Kd was 1.70 +/- 0.03 nmol/L and the mean receptor number (RT) was 122.6 +/- 8.3 fmol/mg protein. In comparison, myometrial tissue examined at the same phase of the cycle had a Kd of 1.3 +/- 0.1 nmol/L and an RT of 205.0 +/- 49.7 fmol/mg protein. Receptors were not detectable in the late luteal phase CL and were significantly lower in the early luteal phase CL (50.7 +/- 6.9 fmol/mg protein), with no difference in the Kd value. Competitive studies with structurally related and nonrelated peptides indicated the presence of specific receptors for OT in baboon CL.(ABSTRACT TRUNCATED AT 250 WORDS)
Khan-Dawood
F S
FS
Department of Obstetrics, Gynecology and Reproductive Sciences, University of Texas Medical School, Houston 77030.
Kanu
E J
EJ
Dawood
M Y
MY
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003338:Corpus Luteum / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D005260:Female; D008183:Luteal Phase / Q000378:metabolism; D010121:Oxytocin / Q000378:metabolism; D010215:Papio; D018045:Receptors, Oxytocin; D017483:Receptors, Vasopressin / Q000378:metabolism*; D014316:Tritium
D018045:Receptors, Oxytocin; D017483:Receptors, Vasopressin; D014316:Tritium; D010121:Oxytocin; D004492:Edetic Acid