Oxytocin receptors in bovine mammary tissue.
Oxytocin receptors were identified and characterized in bovine mammary tissue. [3H]-oxytocin was specifically bound to the 105,000 X g particulate fractions from 5 lactating cows and 5 non-lactating cows. Binding reached equilibrium by 50 min at 20 degrees C and by 8 hr at 4 degrees C. The half-time of displacement at 20 degrees C was approximately 1 hr. ACTH, TRH, angiotensin I, angiotensin II, pentagastrin, bradykinin, xenopsin and L-valyl-histidyl-L-leucyl-L-threonyl- L-prolyl-L-valyl-L-glutamyl-L-lysine were not competitive in the dose range tested at 20 degrees C. The ability of other peptides to inhibit 3H-oxytocin binding was as follows: oxytocin greater than vasotocin greater than arginine - vasopressin greater than lysine - vasopressin greater than Pen1 Phe2 Thr4 - oxytocin. The Kd of the oxytocin receptor averaged 1.66 +/- 1.19 nMol/L for lactating cows and 0.97 +/- nMol/L for non-lactating cows, respectively. The maximum number of binding sites was 0.14 +/- 0.12 nM/mg protein and 0.15 +/- 0.08 nM/mg protein for lactating cows and non-lactating cows, respectively. Identification and characterization of these receptors now makes it possible to study the dynamics of hormonal binding throughout various physiological states of the animal.
Zhao
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Department of Animal Science, Cornell University, Ithaca, NY 14853.
Gorewit
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D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D005260:Female; D007700:Kinetics; D007774:Lactation / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism; D011247:Pregnancy; D011945:Receptors, Angiotensin / Q000378:metabolism*; D018045:Receptors, Oxytocin; D013696:Temperature
D011945:Receptors, Angiotensin; D018045:Receptors, Oxytocin; D010121:Oxytocin