Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding sites for [125I]LHRH were characterized in membranes from the hypthalamus and the effect of estrogen on the binding characteristics was studied in ovariectomized female rats. The radioligand, [125I]LHRH, was found to bind specifically to membranes from the hypothalamus at a maximal level, with an optimal temperature of 0 degrees C and a pH between 7 and 8. The binding was enhanced by NaCl at a concentration of 0.1-0.2 M. The specifically bound [125I]LHRH was only displaced by LHRH, but not by sodium iodide (NaI), bovine serum albumin and other hormones, such as thyrotropin-releasing hormone, bradykinin, oxytocin, prolactin, luteinizing hormone and growth hormone. The divalent metal ions, copper (Cu2+) and mercury (Hg2+), inhibited the specific binding of [125I]LHRH completely, whereas magnesium (Mg2+) and calcium (Ca2+) caused a decrease in binding. As revealed from Scatchard plot analysis, the binding sites for [125I]LHRH in the hypothalamus had a dissociation constant of 0.40 +/- 0.03 microM and the maximum number of binding sites was 98.55 +/- 4.34 pmol/mg protein. Treatment of female rates (ovariectomized for 3 weeks) with 4 micrograms of estradiol benzoate caused a statistically significant decrease in the maximal number of binding sites without any significant effect on the dissociation constant. However, the direct addition of estradiol hemisuccinate to the membrane preparations had no statistically significant effect on the specific binding of [125I]LHRH. The present study provides the evidence that estrogen decreases the density of binding sites for [125I]LHRH in the hypothalamus in vivo.
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PMID:The effect of estrogen on luteinizing hormone-releasing hormone binding sites in hypothalamic membranes. 331 92

1. Ouabain-sensitive 86Rb+ uptake in slices of lactating rabbit mammary gland significantly increased after 20 min or 1 hr of incubation with ovine prolactin (NIH-P-S12; 1 microgram/ml.). 2. Total K+ content of the tissue significantly increased at 20 min of incubation with prolactin. 3. Neither vasopressin nor oxytocin, at concentrations of 2,20 or 40 mui.u./ml., had a significant effect on ouabain-sensitive 86Rb+ uptake or total K+ of the tissue after 30 min or 1 hr of incubation. 4. Tissue slices incubated in cycloheximide at 10 micrograms/ml. for up to 260 min showed a reduction in ouabain-sensitive 86Rb+ uptake and total K+ content, with half-lives of 115 and 63 min, respectively. 5. No consistent in vitro effect of prolactin on (Na+ + K+)-activated ATPase activity in homogenates, crude microsomal fractions or NaI-activated membrane fractions from lactating rabbit mammary gland was found. 6. After 3 hr of incubation of tissue slices in the presence or absence of prolactin (5 micrograms/ml.), no significant differences in the number of [G-3H]ouabain molecules bound per cell (5.2 X 10(4) and 6.2 X 10(4), respectively) or in the dissociation constant (KD) for ouabain binding (5.4 X 10(-7) M and 5.9 X 10(-7) M, respectively) were observed. 7. Incubation of the tissue with cycloheximide (10 micrograms/ml.) for 1-6 hr caused an exponential decrease in [G-3H]ouabain binding with a half-life of 3 hr. 8. It is concluded that prolactin stimulates the activity of the (Na+ + K+)-activated ATPase in slices of lactating rabbit mammary gland within one hour but over this period does not affect the number of ouabain-binding sites, which are apparently turned over with a half-life of 1-3 hr.
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PMID:Effect of prolactin on 86Rb+ uptake, potassium content and [G-3H]ouabain binding of lactating rabbit mammary tissue. 630 27