No abstract

Studies to determine the physiological effects and functions of progesterone started in the twentieth century. Progesterone is a steroid-structured hormone with 21 carbon atoms originating from cholesterol. The corpus luteum, formed after ovulation in ruminants, secretes progesterone, which plays a role in the continuity of the pregnancy. Progestagens can be used for estrus synchronization in cows and heifers. Similarly, they are used for estrus synchronization during the breeding season or outside the breeding season by taking advantage of the negative feedback effect of progesterone in small ruminants. It is applied for the treatment of embryonic deaths due to luteal insufficiency in cows with high milk yield. In anovulatory anestrus, exogenous progesterone applications can be very useful. Progesterone treatment contributes to the resolution of the anestrus by rearranging hypothalamic functions in cattle with follicular cysts. The oxidative stress index in the luteal phase, when progesterone is high in ruminants, is higher than in the follicular phase. In the critical period of pregnancy, a high index of oxidative stress-induced progesterone causes embryonic death. Factors that cause stress in high milk-yielding cows can affect the amount of progesterone synthesis by inhibiting luteal cell function due to excessive free radical production.

SummaryLong-acting GnRH agonists have been used both in canine estrus induction and prevention. The objective of the study was to investigate the clinical and endocrine short-term effects of a deslorelin implant (4.7 and 9.4 mg) in terms of initial "flare-up" in prepubertal bitches. Fourteen healthy, cross-breed prepubertal female dogs, aged 4 months, were used in the study. An implant containing 9.4 mg (G1, n=5) and 4.7 mg (G2, n=4) deslorelin (Suprelorin®) or a placebo (sodium chloride 0.9%, G3, n=5) was inserted subcutaneously. Estrus was monitored once daily by physical and sexual behavioral changes. Vaginal cytology, serum progesterone (P4) and estradiol 17β (E2) concentrations were monitored weekly for the first five weeks throughout the treatment. None of the bitches in the treatment (G1 and G2) and control (G3) group showed any signs of estrous throughout the study period. No local reactions were observed at the implantation site. Two bitches showed an increase in serum P4 concentrations (>1.0 ng/ml) in G1 (2/5; 40%), however, only one of these two animals (P4=6.37 ng/ml) showed an increase in serum E2 concentrations up to 37 pg/ml. No marked increase in serum P4 and E2 concentrations were observed during the first 13 weeks of treatment in G2. These data demonstrate that in prepubertal bitches, insertion of a deslorelin implant does not cause a "flare-up effect" which commonly occurs in anestrus adult bitches during the first month after implantation. However, further studies are needed to demonstrate that the "flare-up" effect of deslorelin implant in bitches especially during later prepubertal stages. Keywords: Prepubertal bitches, Suprelorin®, Flare-up effect Prepubertal Köpeklerde GnRH Analoğu Deslorelinin Kısa DönemKlinik ve Endokrinolojik Etkileri: "Flare-up" Gözlenir mi? ÖzetUzun etkili GnRH agonistleri köpeklerde hem östrusun uyarılmasında hem de baskılanmasında kullanılmaktadırlar. Bu çalışmada, pubertas öncesi dönemdeki dişi köpeklerde deslorelin implant (4.7 ve 9.4 mg) kullanımının "flare-up" dönemi olarak değerlendirilebilecek klinik ve endokrinolojik kısa dönem etkilerinin varlığı araştırılmıştır. Bu amaçla pubertas öncesi dönemde olduğu belirlenen ortalama 4 aylık yaşta on dört adet sağlıklı melez dişi kopek kullanıldı. Köpeklere deri altı yolla 9.4 mg (G1, n=5) ve 4.7 mg (G2, n=4) deslorelin (Suprelorin®) etken maddesi içeren implantlar ya da plasebo (sodyum klorür %0.9; G3; n=5) uygulandı. Östrus belirtileri günlük olarak fiziksel değişiklikler ve davranış değişiklikleri yönünden takip edildi. Ayrıca çalışma süresince vaginal sitoloji, serum progesteron (P4) ve östradiol 17β (E2) konsantrasyonları haftalık olarak izlendi. Tedavi (G1 ve G2) ve kontrol grubundaki (G3) hayvanların hiçbirinde östrus bulgusu belirlenmedi. İmplantın yerleştirildiği bölgede herhangi bir lokal yan etki gözlenmedi. Grup 1'de iki köpekte (2/5; %40) serum P4 düzeyinde bir artış gözlenirken, bu köpeklerden yalnızca birinde (P4=6,37 ng/ml) serum E2 düzeyinin 37 pg/ml'ye kadar yükseldiği belirlendi. Grup 2'de 13 haftal...

Kuru M., Sogukpinar O., Makav M., Cetin N.Effect of barium selenate injections on fertility of Pirlak ewes subjected to estrus synchronization during non-breeding season Summary This study was aimed at determining the effect of barium selenate injections on the fertility of Pirlak ewes which had been subjected to progesterone-assisted estrus synchronization during the non-breeding season. A total of 150 Pirlak ewes between the ages of 2 and 5 years were used in the study. Sponges containing progesterone were inserted into the vaginas of the ewes for 11 (groups I and III) or 14 days (groups II and IV) for the purpose of estrus synchronization, and 500 IU equine chorionic gonadotropin (eCG) was administered on the day of sponge removal. In addition, barium selenate was injected s.c. immediately before estrus synchronization protocol in groups I and III. After the sponges had been removed, estrus was observed for four days. The ewes were mated with fertile rams. The pregnancy was determined by transrectal ultrasonography 30 days after mating. It was observed that the estrus rate, pregnancy rate, conception rate, lambing rate, twinning rate, and litter size were not statistically different (P > 0.05) between the groups, but estrus onset was different (P < 0.001). In conclusion, barium selenate injections did not affect the fertility parameters before progesterone-assisted synchronization was applied to the Pirlak ewes during the non-breeding season.

The goals of this study were as follows: (Experiment 1) to examine the basic capability of canine corpora lutea (CL) to respond to GnRH by assessing expression of gonadotropin-releasing hormone receptor (GnRH-R) in luteal samples collected throughout the luteal lifespan from non-pregnant dogs, and (Experiment 2) to investigate the effects of pre-pubertal application of the GnRH agonist deslorelin acetate on luteal function following the first oestrus. Mature CL were collected during the mid-luteal phase (days 30-45) from treated and control bitches. Transcript levels of several factors were determined: estrogen receptors (ESR1/ERα, ESR2/ERβ), progesterone (P4)-receptor (PGR), prolactin receptor (PRLR), PGE2-synthase (PTGES) and PGE2 receptors (PTGER2/EP2, PTGER4/EP4), vascular endothelial growth factor (VEGFA) and VEGF receptors (VEGFR1 and VEGFR2), cyclooxygenase 2 (COX2/PTGS2), steroidogenic acute regulatory protein (STAR) and 3β-hydroxysteroid dehydrogenase (3βHSD). Additionally, levels of Kisspeptin 1 (Kiss1) and its receptor (KISS1-R) were evaluated. Although generally low, GnRH-R expression was time dependent and was elevated during early dioestrus, with a significant decrease towards luteal regression. In deslorelin-treated and control dogs, its expression was either low or frequently below the detection limit. EP2 and VEGFR1 were higher in the treated group, which could be caused by a feedback mechanism after long-term suppression of reproductive activity. Despite large individual variations, 3βHSD was higher in the deslorelin-treated group. This, along with unchanged STAR expression, was apparently not mirrored in increased luteal functionality, because similar P4 levels were detected in both groups. Finally, the deslorelin-mediated long-term delay of puberty does not have negative carry-over effects on subsequent ovarian functionality in bitches.