The concentrations of catecholamines and oxytocin receptors in the oviduct and its contractile activity in cows during the estrous cycle.

UNLABELLED

In vitro experiments on oviducts of cyclic cows were undertaken to study: (1) the content of dopamine (DA), noradrenaline (NA) and adrenaline (A) in infundibulum, ampulla and isthmus, (2) the concentration of oxytocin receptors (OTR) in oviductal tissues and (3) the motility of ampulla and isthmus. Changes of DA content were observed in the infundibulum and the ampulla with maximal values occurring on Days 6-10 of the estrous cycle. The mean NA content was greatest in infundibulum<ampulla<isthmus. NA concentrations were the highest in the isthmus on Days 1-5 and 16-21, whereas in infundibulum NA levels were low during the whole estrous cycle. Mean A content was the highest (P<0.001) in the isthmus and in the studied regions of the oviduct A content decreased from Days 1-5 to Days 16-21 (P<0.01). Oxytocin receptors densities were measured in oviducts collected from cows on Days 16-21 (277.1+/-151.4 fmol/mg protein; K(d) 20.5+/-10.9 nM). Oxytocin (10(-7) M) increased the area under the contractile curve (AUC) of the ampulla and the isthmus on Days 16-21 and of the isthmus on Days 1-5 (P<0.01). Acetylcholine (Ach) (10(-7) M) stimulated the ampulla and the isthmus contractions on Days 1-5 (P<0.05) and ampulla contractions on Days 6-10 and 16-21 (P<0.01). NA (10(-5) M) relaxed the ampulla and the isthmus during most of the studied days but was most effective on Days 1-5 and 16-21 (P<0.01).

IN CONCLUSION

(a) catecholamine content in the bovine oviduct varies by region and phase of the estrous cycle, (b) the presence of OTR and the stimulatory effect of oxytocin on oviduct motility are evident in the follicular-phase cows, (c) Ach and NA modify contractile activity in the oviduct of cows during follicular and early-luteal phases and (d) the studied oviductal parameters did not differ by ipsilateral and contralateral relationships to the active ovary in cow.