Uterine contractility is strongly influenced by steroids and glucose metabolism: an in vitro study on bovine myometrium.

BACKGROUND: Energetic substrates and hormonal phase are important for uterine contractions. Etomoxir a muscle carnitine palmitoyltransferase-1 inhibitor, able to diverge uterine metabolic pathways towards glycolysis, facilitates glucose utilisation. The aim of this study was to evaluate its effect on uterine contractility in different hormonal situations. METHODS: Uterine samples were collected from 60 cows during follicular phase, luteal phase and pregnancy. The cows were slaughtered at a local abattoir. Longitudinal strips were mounted vertically in a 30-ml organ bath connected to an isometric force transducer. Contractions were recorded with an ink-writing polygraph. After the equilibration period, etomoxir was added to the organ bath at different concentrations. The amplitude and frequency of contractions were registered before and after addition of etomoxir. RESULTS: In 17 strips from pregnant cows, etomoxir increased the amplitude (p < 0.05) of contractions but not the frequency in comparison with basal conditions. In 15 strips from cows in the luteal phase, etomoxir increased the amplitude (p < 0.05) and frequency of contractions (p < 0.05 at 5 µM and p < 0.01 at 8 and 10 µM). In 18 strips from cows in the follicular phase, etomoxir increased the frequency of contractions but not the amplitude (p < 0.01 at 5 µM and p < 0.05 at 8 and 10 µM). CONCLUSIONS: This study confirms the importance of glucose for uterine contractility and, moreover, it underlines different patterns of contraction with regard to the hormonal status.

Reactive oxygen species (ROS): involvement in bovine follicular cysts etiopathogenesis.

Ovulation is compared to an acute inflammatory process during which vasoactive agents, prostanoids, leukotrienes and Reactive Oxygen Species (ROS) develop. The aim of this study was to evaluate the levels of ROS in cystic and follicular fluid, in order to establish their involvement in the etiopathogenesis of Cystic Ovarian Follicle (COF) in dairy cows. The study was conducted in 30 healthy cows (group C) and 30 cows affected by COF (group COF). The fluid of follicular cysts and of preovulatory follicles was drawn by means of ultrasound guided aspiration from the cows of both groups. The fluid obtained was analyzed by a photometric analytical system to detect ROS level. ROS concentration was statistically lower in the cystic fluid than in the follicular one (62.4 +/- 13.36 U.Carr vs. 84.89 +/- 26.99 U.Carr) (p<0.05), thus suggesting that an alteration of the cascade responsible for ROS production may be implicated in the complex etipathogenesis of COF.

Serum levels of reactive oxygen species (ROS) in the bitch.

The aim of this study was to determine the serum concentrations of reactive oxygen species (ROS) during the different phases of the estrous cycle in the bitch, in order to establish their physiological values. 56 healthy mixed-breed bitches were enrolled at this purpose and divided into 4 groups, standing on the different phases of the estrus cycle. Blood samples were collected in all groups and serum ROS concentrations were determined. Proestral concentrations were statistically higher than anestral ones, and statistically lower than those found in estrus (p<0.001). The highest concentrations of ROS were detected at estrus, that is, in the peri-ovulatory period. This sharp increase in ROS concentrations is related to the acute inflammatory process underlying ovulation and to the increase in immune and metabolic activities, cytological changes and myometrial contractility promoted by the high levels of estrogens. In diestrus, the mean concentration of ROS decreases. This reduction did not show any statistically significant difference with the mean value observed in proestrus. In this phase, in fact, the high concentrations of progesterone, exerting an antioxidant and immunodepressive effect, justify the lower mean concentration of ROS detected. In anestrus, the lowest concentrations of ROS were observed, for the reduced metabolic and endocrine activity occurring in this phase of the estrous cycle. In conclusion our results establish the physiologic levels of ROS during the estrous cycle in the bitch and reflect the endocrine morphologic and metabolic changes occurring during it.

Thyreotropic effect of human Chorionic Gonadotropin (hCG) in mares at estrus.

The beta-subunits of thyroid stimulating hormone (TSH) and human chorionic gonadotropin (hCG) share a high homology, just like the ectodomains of their receptors, do. As a consequence, hCG was shown to exert a thyrotropic action in humans and hamsters. This study aimed to investigate whether hCG, used to induce ovulation, displays a thyrotropic effect in the equine species too. Forty mares at estrus were divided in two groups; 20 were intravenously treated with sterile saline solution (NaCl 0.9%) (group A); 20 were intravenously treated with 4000 I.U. of hCG (group B). All the mares were artificially inseminated 24 hours after the administration of the drugs and underwent blood collection at estrus detection (T1), 2, 6, 24 hours later (T2, T3, T4), and 3 and 6 days later (T5, T6), in order to detect serum fT3 and fT4 concentrations. fT3 concentrations gave rise to similar and constant trends in the two groups, without any statistically significant difference, whereas fT4 concentrations declined in both groups, remaining statistically higher in group B than in group A for 48 hours (p < 0.05), thus accounting for a thyrotropic effect of hCG. Pregnancy rate was 70% in group B and 40% in group A, respectively. The higher success in the outcome of pregnancy may result from the immunomodulating and steroidogenic effects of hCG and from the higher levels of thyroid hormones observed in the hCG treated group.

Effects of antibiotics on biochemical parameters, leukocytes and reactive oxygen species (ROS) in bitches after ovariectomy.

It is well known that following surgical procedures, a variety of patho-physiological alterations occurs in the host, such as changes in haemodynamic, endocrine and immune functions, as well as increase in Reactive Oxygen Species (ROS). Antibiotic administration, a common practice used in surgery, affects immune functions and ROS generation. Our study was aimed to investigate the effect of five different antibiotic regimens: amoxicillin, benzylpenicillin/dihydrostreptomycin, sulfametazine/sulfamerazine/ sulfathiazole, enrofloxacin, lincomycin/spectinomycin, administered twice (2 hours before skin incision and 6 hours after the end of the surgical suture), on biochemical parameters, leukocytes and ROS concentrations, in bitches undergoing open laparotomic ovariectomy. All treated bitches recovered from surgery without developing either systemic dysfunctions, or infections at the surgical site. Mean healing time was 7 +/- 3 days. An increase in white blood cell count, in differential leukocyte count and in ROS concentrations occurred 24 hours after the end of surgery, followed by a gradual decrease to basal values within the fourth day after surgery. The biochemical parameters remained quite constant throughout the study. In conclusion, our results show that the above antibiotic regimens, administered only twice, are efficient in inducing an uneventful recovery after laparotomic ovariectomy and preventing the development of infections in the bitch.

First demonstration of an increased serum level of reactive oxygen species during the peripartal period in the ewes.

Reactive Oxygen Species (ROS) are produced during oxidative metabolism, and regulate many biological processes. The acute inflammation characterizing parturition induces many physiological changes. Among them, there is evidence that ROS affect the synthesis of many factors involved in parturition. Our study aims to determine serum levels of ROS in periparturient ewes, as well as to establish a value of reference of their physiological concentration. ROS determination was performed on blood collected every 12 hours in periparturient twin pregnant ewes. Our results will show a significant increase in ROS concentrations from the beginning to the end of the experiment. This increase may be due to the inflammatory process establishing during parturition.

In vitro effects of L-arginine on spontaneous and homocysteine-induced contractility of pregnant canine uteri.

The L-Arginine-Nitric Oxide Synthase-Nitric Oxide (L-Arg-NOS-NO) system exerts a pivotal role in the maintenance of uterine quiescence during pregnancy, whereas Homocysteine (Hcy) promotes uterine contractility. The aim of this study was to test the in vitro effects of L-Arg on spontaneous and Hcy-induced contractions of uteri excised from pregnant bitches. 104 strips cut from pregnant uteri were mounted in an organ bath. 40 out of 104 strips (16 from mid-gestation uteri and 24 from close to term uteri, respectively) were exposed to cumulative doses of L-Arg; 40 strips (16 from mid-gestation-uteri and 24 from close to term-uteri, respectively) were exposed to N-nitro-L-arginine methyl ester (L-NAME), a NOS antagonist; the remaining 24 strips (from close-to-term uteri) were first exposed to a single dose of Hcy and then to increasing doses of L-Arg. L-Arg showed no effects on spontaneous contractility both in mid-gestation- and close to term-uterine strips, whereas it promoted a relaxant effect on Hcy-induced contractility. On the contrary, L-NAME increased amplitude of contraction both in mid-gestation and close to term strips. These findings suggest that the L-Arg-NO system is present in the uterus of pregnant bitches and that Hcy is able to modulate its actions. Further investigation of this system may provide the basis of future obstetrical therapies in bitches.