Expression of receptors for ovarian steroids and prostaglandin E2 in the endometrium and myometrium of mares during estrus, diestrus and early pregnancy.

The objective of this study was to compare expression of estrogen receptor alpha (ER-α), ß (ER-ß), progesterone receptor (PR), as well as prostaglandin E2 type 2 (EP2) and 4 (EP4) receptors in the equine myometrium and endometrium during estrus, diestrus and early pregnancy. Tissues were collected during estrus, diestrus, and early pregnancy. Transcripts for ER-α (ESR1), ER-ß (ESR2), PR (PGR), EP2 (PTGER2) and EP4 (PTGER4) were quantified by qPCR. Immunohistochemistry was used to localize ER-α, ER-ß, PR, EP2 and EP4. Differences in transcript in endometrium and myometrium were compared by the ΔΔCT method. Expression for ESR1 (P<0.05) tended to be higher during estrus than diestrus in the endometrium (P=0.1) and myometrium (P=0.06). In addition, ESR1 expression was greater during estrus than pregnancy (P<0.05) in the endometrium and tended to be higher in estrus compared to pregnancy in the myometrium (P=0.1). Expression for PGR was greater (P<0.05) in the endometrium during estrus and diestrus than during pregnancy. In the myometrium, PGR expression was greater in estrus than pregnancy (P=0.05) and tended to be higher during diestrus in relation to pregnancy (P=0.07). There were no differences among reproductive stages in ESR2, PTGER2 and PTGER4 mRNA expression (P>0.05). Immunolabeling in the endometrium appeared to be more intense for ER-α during estrus than diestrus and pregnancy. In addition, immunostaining for PR during pregnancy appeared to be more intense in the stroma and less intense in glands and epithelium compared to estrus and diestrus. EP2 immunoreactivity appeared to be more intense during early pregnancy in both endometrium and myometrium, whereas weak immunolabeling for EP4 was noted across reproductive stages. This study demonstrates differential regulation of estrogen receptor (ER) and PR in the myometrium and endometrium during the reproductive cycle and pregnancy as well as abundant protein expression of EP2 in the endometrium and myometrium during early pregnancy in mares.

Progesterone production in mares and echographic evaluation of the corpora lutea formed after follicular aspiration.

Ultrasound-guided follicular aspiration was performed in 26 Criollo crossbred mares, followed by the evaluation of ultrasonographic images of the Corpus luteum (CL) that was formed after puncture of follicles of different diameters (Group 25-29 mm; Group 30-35 mm and Group >35 mm). Serum progesterone (P(4) ) concentrations were measured to determine CL function. The size of the CL was measured and the CL was classified based on the following echoscore: 1- anechoic tissue; 2- poorly defined luteal structure with low echogenicity; 3- echogenicity analogous to a luteal structure. The proportion of aspirated follicles that formed a functional CL (based on P(4) concentration) 8 days after aspiration was 57.1% (4/7; CL size 25-29 mm), 75.0% (6/8; CL size 30-35 mm) and 72.7% (8/11; CL size >35 mm), respectively (p > 0.05). The echographic scores of aspirated follicles (indicating the presence or absence of a CL) were consistent with serum P(4) concentrations (p < 0.0001). Of 26 aspirations, 18 resulted in luteal function confirmed by increased progesterone concentrations ([P(4) ] > 1.0 ng/ml); 17 of these mares (94.4%) had an echoscore (2-3) compatible with luteinization (p = 0.0372). Eight days after aspiration, serum [P(4) ] > 2.0 ng/ml was associated with high (p = 0.0056) CL echoscore (3) in 15 of 17 mares (88.2%). The echoscore used in this study was valuable as a screening test to detect the presence of a functional CL after aspiration. An echoscore of 3 served as a practical and efficient method to confirm luteinization.

Luteal function induced by transvaginal ultrasonic-guided follicular aspiration in mares.

Ultrasonic-guided transvaginal follicle aspiration was performed in 58 crossbreed mares in order to determine whether aspiration of various dominant follicle diameters resulted in luteal tissue capable of producing progesterone (P(4)). The mares were randomly assigned to three groups according to follicular diameter (25-29 mm; 30-35 mm and >35 mm). Mares that had ovulations naturally served as controls. The serum progesterone (P(4)) concentrations in the aspirated mares were greater (P < 0.0001; r(2) = 0.6687; CV = 21.52) in mares with natural ovulation compared to mares with aspirated follicles regardless of groups. Serum P(4) concentration in aspired mares with follicular diameter of 25-29 mm declined 0.365 ng/ml/day (P = 0.0065) from the day of aspiration (D0) up to D8. In mares with follicle diameter of 30-35 mm, serum P(4) concentration increased (0.258 ng/ml/day; P = 0.001), as well as in the mares with follicles >35 mm diameter (0.481 ng/ml/day; P < 0.0001), and in mares with natural ovulation (1.236 ng/ml/day; P < 0.0001). Out of the 25 mares with follicular aspirations that formed Corpora hemorragica (P(4) >1 ng/ml), 23 (92%) had greater (>2 ng/ml) serum P(4) concentrations on Day 8 after aspiration. Of these 23 mares, 75% were in the 25-29 mm group, 9/10 (90%) in the 30-35 mm group, and 11/11 (100%) of the mares in the >35 mm follicular diameter group had luteinization (P(4) >2 ng/ml). These results suggest that a functional Corpus luteum can be induced in mares using follicular aspiration and that a minimum 35 mm follicular diameter is needed to reach a progesterone serum concentration compatible with that of a Corpus luteum produced by natural ovulation.

Induction of parturition in alpacas and subsequent survival of neonates.

OBJECTIVE: To evaluate use of fluprostenol, dexamethasone, and oxytocin for induction of parturition in alpacas, and to determine viability of the newborn crias. DESIGN: Prospective, randomized, controlled trial. ANIMALS: 36 pregnant alpacas within 10 days of parturition. PROCEDURE: Animals were randomly assigned to treatment groups. Plasma progesterone and plasma and urine estrone sulfate concentrations were measured for 5 days after treatment. Clinical signs of the neonates were determined. RESULTS: Time between treatment and parturition was significantly shorter for animals that received fluprostenol than for animals in any other group. The highest dose of dexamethasone (0.5 mg) caused fetal death. None of the other treatments induced early parturition. Time between birth and first suckling, body weight, rectal temperature, pulse rate, and respiratory rate at birth and serum IgG concentration 24 hours after birth were not different between crias born after fluprostenol treatment and crias born to control alpacas. CLINICAL IMPLICATIONS: Fluprostenol was effective at inducing parturition in these alpacas, but dexamethasone and oxytocin were not. Crias born after fluprostenol treatment were similar to crias born to control alpacas.