Electrophoretic characterization of proteins in oviduct fluid of cows during the estrous cycle

This study was undertaken to examine the in vivo protein composition of the bovine oviduct during the estrous cycle. Oviduct fluid was collected daily from four oviduct-cannulated dairy cows for a total of four complete estrous cycles. Fluid secretion followed a definite cyclic pattern, with maximum secretion occurring at estrus in all cycles. Protein concentration fluctuated during the cycle and varied among animals. In general, protein concentration was lower at the time of estrus. Total protein in oviduct fluid, however, was higher around estrus, indicating increased transudation or secretion by the oviduct. One-dimensional SDS-PAGE separation revealed the protein pattern of oviduct fluid to be generally similar to that of blood serum and follicular fluid. Two proteins appeared to be oviduct-specific. The first, a protein of approximately 47 kDa, was evident in oviduct fluid throughout the estrous cycle. The second protein, evident as a broad diffuse staining band above albumin, appeared for only 3-4 days at or near ovulation. This protein had a molecular weight of 80-95 kDa and stained positive for carbohydrate with periodic acid-Schiff reagent. These studies indicate that the in vivo protein composition of oviduct fluid varies with the estrous cycle, and that around estrus, an oviduct-specific glycoprotein is present.     

Identification,characterization and localization of three proteins expressed by the porcine oviduct

At estrus, the oviduct undergoes endocrine-induced changes which provide an essential microenvironment for maturation of gametes, fertilization and embryonic development. Several oviduct expressed proteins which interact with gametes or embryos, including the oviduct-specific, estrogen-dependent glycoprotein (OGP), have been identified and characterized. The objective of the present study was to identify, characterize and localize other proteins expressed by the porcine oviduct during estrus that may function in an autocrine or paracrine manner to enhance fertilization and embryonic development. Oviducts were collected during the estrous cycle or early pregnancy, flushed and divided into functional segments, and portions of the infundibulum, ampulla and isthmus were fixed for immunocytochemical analysis or cultured. Culture media was semi-purified by heparin-agarose affinity chromatography, proteins were transferred to polyvinylidene fluoride (PVDF) membrane after two-dimensional (2D)-SDS-PAGE and three different proteins were identified, excised and subjected to N-terminal amino acid analysis. These proteins were identified as complement component C3b, the carboxy-terminal propeptide of alpha 1 (III) procollagen (PIIICP), and the heavy chain variable region of IgA. Electrophoresis and fluorography of media from Days 0 to 12 of early pregnancy or the estrous cycle revealed both spatial and temporal expression of C3b and IgA heavy chain but not PIIICP by the oviduct. Further, all three proteins were identified in oviduct fluid by electrophoresis, immunoblot or immunoprecipitation analysis. Complement component C3b and IgA heavy chain were immunolocalized in all three oviduct segments on all days; however, temporal and spatial differences were demonstrated. Staining was greater in the infundibulum and during estrus for all three identified proteins. In summary, three proteins expressed by the oviduct at estrus and during early pregnancy were identified; characterization and localization suggest they may play a critical role in protecting the luminal environment, participating in ECM remodeling and gamete interactions.     

Distribution of NADPH-diaphorase and nitric oxide synthase (NOS) in different regions of porcine oviduct during the estrous cycle.

Nitric oxide synthase (NOS) is responsible for the biological production of nitric oxide (NO) in several organs, including those of the reproductive tract. We investigated potential changes in NADPH-diaphorase (NADPH-d) activity (marker for NOS activity) and the presence and distribution of NOS in the porcine oviduct. Tissues were obtained from gilts (n=16) on different days of the estrous cycle. One fallopian tube was used for histo- and immunohistochemistry and the other for Western blotting analysis. NADPH-d activity was much higher in the epithelium of the mucosa than in the myosalpinx. The highest activity of NADPH-d was always found in the epithelium of the isthmus. The intensity of the reaction (arbitrary units +/- SEM) in isthmus epithelium increased from the postovulatory period until early proestrus (96.2 +/- 11.2) and then gradually decreased. The lowest intensity of NADPH-d reaction in the epithelium of the isthmus was seen at estrus (58.4 +/- 7.7). The most intense NADPH-d activity in myosalpinx of all parts of the oviduct was observed at the postovulatory stage of the estrous cycle (isthmus 38.3 +/- 2.5; ampulla 35.6 +/- 4.2; infundibulum 24.7 +/- 0.8) and then decreased during the remaining stages of the estrous cycle (p< 0.001). The presence of endothelial NOS (eNOS) was detected in epithelial cells of mucosa and in endothelium of vascular tissues and myosalpinx during all studied days of the estrous cycle. The positive reaction for inducible NOS (iNOS) was restricted only to the endothelium of lymph vessels and some blood vessels. Because our Western blotting analysis revealed that porcine oviduct contains eNOS but not iNOS, we suggest that eNOS is the main isoform of NOS expressed in the porcine oviduct. We concluded that the different activity of NADPH-d in the various regions of the oviduct, accompanied by changes in its activity during the course of the estrous cycle, could indicate an important role of NO in regulation of tubal function.     

Capacitation of bovine spermatozoa by oviduct fluid

Oviduct fluid collected from chronically cannulated oviducts of heifers was evaluated for its effect on capacitation of bovine sperm in vitro. Capacitation was determined by the ability of sperm to fertilize bovine oocytes in vitro and to undergo an acrosome reaction (AR) upon exposure to lysophosphatidylcholine (LC). After incubation of sperm with 0-25% (v/v) estrual oviduct fluid (collected +/- 1 day from estrus) for 4 h, addition of LC (100 micrograms/ml) for an additional 0.25 h resulted in an increasing percentage of acrosome-reacted sperm as the concentration of oviduct fluid increased. Sperm incubated 4 h with 25% estrual oviduct fluid fertilized more oocytes than sperm incubated in medium alone (p less than 0.05) but was not different from sperm incubated with 10 micrograms/ml heparin (p greater than 0.05). Glucose inhibited the ability of LC to induce ARs in sperm incubated 4 h with heparin or estrual oviduct fluid. Incubation of sperm with 25% oviduct fluid collected at various days over the estrous cycle demonstrated that peak capacitating activity was found at estrus but was also present +/- 1 day from estrus. The active capacitating factor in oviduct fluid was found to be heat stable. In addition, when extraction procedures were applied in sequential order, oviduct fluid capacitating activity was resistant to protease digestion, precipitable by ethanol, size-excluded by Sephadex G-25, and destroyed by nitrous acid. These results suggest that a heparin-like glycosaminoglycan from the oviduct is a potential in vivo capacitating agent in the bovine.     

In vitro and in vivo association of an oviduct estrus-associated protein with bovine zona pellucida

The interaction between the bovine egg zona pellucida and a 97 kDa estrus-associated protein produced by the oviduct was examined in vitro and in vivo. In vitro matured bovine eggs were incubated with oviduct fluid recovered throughout the estrous cycle from separate indwelling cannulae placed in the ampulla and isthmus of the same oviduct. Immunofluorescence techniques and a polyclonal antiserum against the 97 kDa protein were used to localize this protein on washed eggs previously incubated with oviduct fluid. Intensity and distribution of immunofluorescence varied with stage of cycle and to a lesser degree with region of oviduct from which the oviduct fluid was obtained. The most intense fluorescence was observed on the zonae pellucidae of eggs incubated with oviduct fluid pooled from days near estrus and ovulation compared to fluid pooled from luteal stage days. The immunofluorescence of isthmus-derived oviduct fluid was more intense than was ampulla-derived oviduct fluid collected near estrus. The zonae pellucidae of 7-day-old embryos flushed from the uterus displayed immunofluorescence comparable to that observed on the zonae pellucidae of eggs incubated in vitro with peri-estrus oviduct fluid. No immunofluorescence was observed associated with the perivitelline space, egg cytoplasm, or blastomeres. The apparent uptake of a 97 kDa estrus-associated protein by the zonae pellucidae of eggs in vitro and embryos in vivo may indicate that this protein functions in fertilization and/or early embryo development.     

Detection of glycosyltransferases in the golden hamster (Mesocricetus auratus) oviduct and evidence for the regulation of O-glycan biosynthesis during the estrous cycle

Recently, we provided evidence that the glycosylation of hamster oviductin, a member of the mucin family of glycoproteins, is regulated during the estrous cycle. In order to further elucidate the glycosylation process of oviductal glycoproteins, we identified biosynthetic pathways involved in the assembly of mucin-type O-linked oligosaccharide (O-glycan) chains in the hamster oviduct. Our results demonstrated that the hamster oviduct has high activities of glycosyltransferases that synthesize O-glycans with core 1, 2, 3 and 4 structures as well as elongated structures. Oviduct therefore represents a typical mucin-secreting tissue. Our results also showed that specific glycosyltransferase activities are regulated during the estrous cycle. Mucin-type core 2 beta6-GlcNAc-transferase (C2GnT2) is responsible for synthesizing core 2 and core 4 structures in the oviduct. Specific assays for C2GnT2 revealed a cyclical pattern throughout the estrous cycle with high activity at the stages of proestrus and estrus and low activity at diestrus 1. Using semiquantitative RT-PCR, the mRNA levels for C2GnT2 in the estrous cycle stages could be correlated with the enzyme activities. An increase in glycosyltransferase activity in the hamster oviduct at the time of ovulation suggests that glycosylation of oviductal glycoproteins may be necessary for these proteins to exert their functions during the process of fertilization.     

Identification and content of insulin-like growth factors in porcine oviductal fluid.

Oviductal fluid (OvF) was collected from gilts by indwelling catheters during the estrous cycle and analyzed for content of insulin-like growth factors (IGF-I, IGF-II). Group 1, composed of 9 gilts in a summer environment near a boar, yielded mean daily fluid volumes of 1.18 +/- 0.16 ml during estrus and 0.69 +/- 0.03 ml post-estrus. Group 2, composed of 7 gilts in a moderate-temperature, light-regulated room, yielded 1.20 +/- 0.18 ml during estrus and then OvF flow essentially stopped. Serum samples were also collected 2 times daily during the cycle and analyzed along with the OvF for IGF-I and IGF-II. Serum was also analyzed for estradiol-17 beta (E2). For group 1, OvF content (concentration x fluid volume) of IGF-I and IGF-II was greater (p less than 0.05) at estrus than pre- and post-estrus. Daily mean content values (ng/day) for IGF-I and IGF-II during peri-estrus were 30.9 +/- 6.3 and 62.2 +/- 12.3, respectively. During nonestrus, values were 6.8 +/- 6.3 and 11.7 +/- 12.3, respectively. For group 2, OvF content of IGF-I and IGF-II during estrus was similar to that of group 1. Whereas IGF content differed between estrus and nonestrus periods, IGF concentrations were similar (p greater than 0.05), a finding that results from the difference in OvF produced. Compared with OvF concentrations of IGF for a given pig, blood plasma concentrations of IGF-I and IGF-II were 2- to 5-fold higher in the plasma sample collected the same day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antioxidant defenses are modulated in the cow oviduct during the estrous cycle

The balanced presence of reactive oxygen species and antioxidants has a positive impact on sperm functions, oocyte maturation, fertilization, and embryo development in vitro. The mammalian oviduct is likely to provide an optimal environment for final gamete maturation, sperm-egg fusion, and early embryonic development. However, the expression and distribution of antioxidant enzymes in the bovine oviduct are poorly characterized. We analyzed the mRNA expression and enzymatic activities of major antioxidants glutathione peroxidase (GPx), superoxide dismutase (Cu,ZnSOD), and catalase in the bovine oviduct throughout the estrous cycle. The high levels of expression for GPx-3 in the isthmus were in contrast to expression of GPx-1 and GPx-2, which occurred mostly in the ampulla and infundibulum of the oviduct. The highest levels of mRNA expression for GPx-1 were observed toward the end of the estrous cycle before ovulation, whereas GPx-2 was mostly expressed at midcycle. Catalase and Cu,ZnSOD mRNA analyses revealed a homogenous expression along the oviduct. The highest levels of glutathione and enzymatic activities for GPx and catalase occurred at the middle (10-12 days) and end (18-20 days) of the estrous cycle, whereas total SOD activity remained constant throughout the estrous cycle in the oviductal fluids. These findings underscore the importance of hydrogen peroxide and hydroperoxide removal by GPx in the oviduct. The heterogeneous expression of antioxidants such as GPx along the oviduct is a possible indication of their physiological role in the events leading to successful fertilization and implantation in vivo.     

Nuclear estrogen and progesterone receptors in the oviduct of heifers under natural and superovulated estrous cycles

Oviducts from 22 crossbred heifers were examined for the presence of nuclear estrogen (ERalpha) and progesterone (PR) receptors at different phases (estrus, metaestrus and diestrus) of naturally occurring estrous cycles and estrous cycles during which superovulation was induced. Receptors were detected by immunohistochemistry in the epithelial cells, connective tissue and muscular layer of oviductal infundibulum, ampulla, ampullary/isthmic transition and isthmus. Epithelial ERalpha was found along the entire oviduct regardless of the cycle phase and of the circulating concentrations of 17beta-estradiol (E(2)) and progesterone (P(4)). Epithelial PR was found mainly at the ampullary-isthmic transition and isthmus and more intensely at the estrus phase but their amount was not correlated with P(4) concentrations. ERalpha in the connective tissue was more abundant at the infundibulum and ampulla, regardless of the phase of the estrous cycle and of E(2) and P(4) circulating concentrations. PR in the connective tissue was found mostly at the ampulla, regardless of the estrous cycle phase but no correlations were found between amount and P(4) concentrations. ERalpha staining intensity in the muscular layer was similar at all phases of the estrous cycle and at all anatomical segments of the oviducts. However, PR staining was more intense at the isthmus during the metaestrus phase and it was negatively correlated with P(4) concentrations. In general, data from the present research suggest that P(4) exerts an inhibitory role upon ERalpha and PR. Also, no differences were found between animals subjected or not to superovulation.     

Concentrations of 13, 14-dihydro-15-keto-prostaglandin F(2)alpha, estradiol-17beta and progesterone during the peripubertal period in heifers

Twenty prepubertal Holstein heifers were utilized to assess plasma 13, 14-dihydro-15-keto-prostaglandin F(2)alpha (PGFM), serum progesterone (P(4)) and estradiol-17beta (E(2)) concentrations as well as the E(2):P(4) ratio during the onset of puberty in cattle. All animals were maintained as a group along with a sterile marker bull to assist in the detection of estrus. Upon detection of the first estrus (Day=O), daily blood samples were collected from a jugular vein until the heifers had completed 3 estrous cycles. The average body weight and age at first estrus were 247.6+/-4.8 kg and 304.0+/-7.5 days, respectively. Frequency of abnormal length estrous cycles was greater (P<0.02) during the first (40%) and second (35%) cycles than during the third estrous cycle (0%). All heifers had normal cycle lengths (18 to 24 days) by the third estrous cycle. Serum P(4) was greater during the third cycle (P<0.05) from Day 10 to Day 4 before the next estrus compared with the same period of the first estrous cycle. Serum E(2) did not peak until the day of estrus in the first cycle, whereas E(2) reached a maximal level 2 days before estrus in the third estrous cycle. Serum E(2) was higher (P<0.0001) 2 days before estrus in the third cycle than in the first estrous cycle. Plasma PGFM reached maximum concentrations 3 days before estrus in the third cycle compared with 1 day before estrus at the end of first estrous cycle. As estrus approached during the third cycle, PGFM rose 1 day before E(2) rose and P(4) declined, while the rise in PGFM and E(2) occurred simultaneously, with P(4) declining at the end of the first estrous cycle. During diestrus, the E(2):P(4) ratio was lower (P<0.07) in the third cycle than in the first, but it was higher (P<0.04) at estrus and 1 day before in the third estrous cycle. These data reveal a high incidence of abnormal length estrous cycles during the first two estrous cycles of the peripubertal period, and demonstrate anomalies in uterine and ovarian endocrine activity during the peripubertal period in cattle.     

In situ oviduct and uterine pH in cattle

Knowledge of oviduct and uterine pH in cattle is lacking mainly because of the difficulty of accessing these reproductive tissues, which for the oviduct at least necessitates anesthesia. Because halothane anesthesia is known to depress respiratory function and thus increase blood CO2 and decrease pH, oviduct and uterine pH was measured both in the presence and absence of halothane. Using short-term anesthesia with thiopentone only, oviduct pH was measured on days 2-4 of the estrous cycle and uterine pH on days 6 and 8; there was no significant effect of day of the cycle but oviduct pH ( 7.60+/-0.010 ) was greater ( P<0.001 ) than uterine pH ( 6.96+/-0.009 ). Oviduct pH was higher ( P<0.001 ) and uterine pH lower ( P<0.001 ) than venous blood pH ( 7.41+/-0.007 ). Using thiopentone/halothane anesthesia, oviduct pH was measured on days 0, 2, 3, 4 and 6, and uterine pH on days 6, 8 and 14; there was no effect of day of cycle but oviduct pH values were generally higher than uterine values and significantly so ( P<0.001 ) on day 6 where direct comparison was possible. To our knowledge these are the first published in situ measurements of oviduct pH in cattle.     

GRP78 expression and immunohistochemical localization in the female reproductive tract of mice

The 78-kDa glucose-regulated protein (GRP78) is an endoplasmic reticulum chaperone, with multiple functional roles in protein processing and provision of cellular protection. However, the physiological role of GRP78 in embryo development is not clear. Localization of GRP78 and expression of its mRNA in the reproductive organs throughout the estrous cycle in mice were investigated by immunohistochemistry and real-time polymerase chain reaction, respectively. Whereas there was intense staining for GRP78 in the oviduct at estrus, the ciliated cells of isthmus had better staining than those of infundibulum and ampulla at all phases of the cycle. Furthermore, GRP78 was located in the uterine luminal and glandular epithelial cells throughout the estrous cycle, particularly during the estrus phase. However, levels of GRP78 mRNA in the oviduct and uterus varied during the cycle, with peaks at estrus. In conclusion, GRP78 expression varied with the phase of the murine estrous cycle; this might be related to gamete transport, fertilization and early development of the zygote/embryo.     

Relationships between insulin and glucose metabolism and pituitary-ovarian functions in fasted heifers

The effects of fasting between Days 8 and 16 of the estrous cycle on plasma concentrations of luteinizing hormone (LH), progesterone, cortisol, glucose and insulin were determined in 4 fasted and 4 control heifers during an estrous cycle of fasting and in the subsequent cycle after fasting. Cortisol levels were unaffected by fasting. Concentrations of insulin and glucose, however, were decreased (p less than 0.05) by 12 and 36 h, respectively, after fasting was begun and did not return to control values until 12 h (insulin) and 4 to 7 days (glucose) after fasting ended. Concentrations of progesterone were greater (p less than 0.05) in fasted than in control heifers from Day 10 to 15 of the estrous cycle during fasting, while LH levels were lower (p less than 0.01) in fasted than in control heifers during the last 24 h of fasting. Concentrations of LH increased (p less than 0.01) abruptly in fasted heifers in the first 4 h after they were refed on Day 16 of the fasted cycle. Concentrations (means +/- SEM) of LH also were greater (p less than 0.05) in fasted (11.2 +/- 2.6 ng/ml) than in control (4.7 +/- 1.2 ng/ml) heifers during estrus of the cycle after fasting; this elevated LH was preceded by a rebound response in insulin levels in the fasted-refed heifers, with insulin increasing from 176 +/- 35 pg/ml to 1302 +/- 280 pg/ml between refeeding and estrus of the cycle after fasting. Concentrations of LH, glucose and insulin were similar in both groups after Day 2 of the postfasting cycle. Concentrations of progesterone in two fasted heifers and controls were similar during the cycle after fasting, whereas concentrations in the other fasted heifers were less than 1 ng/ml until Day 10, indicating delayed ovulation and (or) reduced luteal function. Thus, aberrant pituitary and luteal functions in fasted heifers were associated with concurrent fasting-induced changes in insulin and glucose metabolism.     

Pregnancy rates and sexual behavior under pasture breeding conditions in mares

Pony mares (n=480) and 16 stallions were assigned to four herds of 60 mares and one stallion (large herds) and to 12 herds of 20 mares and one stallion (small herds). The stallions remained with the herds continuously for all of the large herds and seven of the small herds. In the five remaining small herds the stallion was put into a herd for three hours every two days for 12 observation periods. Pregnancy rates and day of ovulation were estimated by size of embryonal enlargements. Mean pregnancy rates of 51% and 54% were obtained in the small herds and 42% in the large herds during a 48-day period (equivalent to two estrous cycles). Pregnancy rates for herds with the stallion present continuously were higher (P<0.01) for the small herds than for the large herds for days 1-24 (42% versus 19%). There was no effect of herd size on number of mares becoming pregnant per herd on days 1-24, but more mares (P<0.01) became pregnant during days 25-48 in the large herds (13.2 mares per herd versus 1.8). In the herds in which the stallion was present intermittently, the number of times that the stallion rebred the same mare when more than one mare was in estrus was greater (P<0.01) than what would be expected to occur by chance (observed, 21%; expected, 11%). Repeated breeding of the same mare seemed related to the availability or activity of the mare, since such mares more frequently followed and positioned themselves in the vicinity of the stallion. Most of the interferences by a mare which involved keeping the stallion and another mare apart were directed at the mare, whereas most of the interferences during mounting were directed at the stallion (P<0.01). Mares were more likely (P<0.01) to interfere when in estrus than when in nonestrus. When interfering mares were in nonestrus, their hostility was usually directed at the stallion (92%), whereas when in estrus their interference was more frequently directed at a mare (73%, P<0.01).     

Sperm migration into and through the oviduct following artificial insemination at different stages of the estrous cycle in the rat

In order to examine whether sperm migration into and through the oviduct follows an invariable pattern or is subject to regulation, rats in proestrus, estrus, metestrus, or diestrus were inseminated in the upper third of each uterine horn with 10-20 million epididymal spermatozoa. Three or eight hours later, the numbers of spermatozoa free and adhering to the epithelium in the ampullary and isthmic segments were determined. A significantly higher number of spermatozoa were recovered in estrus than in other stages, at 3 h than at 8 h, and at all stages from the isthmus than from the ampulla. Spermatozoa adhering to the epithelium were observed only in proestrus and estrus and in the isthmus. The effect of exogenous estradiol-17beta (E2) and progesterone (P4) on sperm migration was investigated in rats in which the estrous cycle was inhibited pharmacologically. E2 facilitated sperm migration into the oviduct and P4 antagonized this effect, whereas P4 alone had no effect. Concomitant treatment with E2+P4 induced adhesion of spermatozoa to the oviductal epithelium. In conclusion, the pattern of sperm migration into and through the rat oviduct varies with the stage of the cycle, being dependent on E2 and P4. The adhesion of spermatozoa to the rat oviductal epithelium is stage- and segment-specific and requires the combined action of both hormones.     

Luteal competency during the resumption of ovarian cyclicity in postpartum Brahman cows

Twenty pluriparous, spring-calving Brahman cows were used to determine luteal competency, as measured by serum progesterone concentrations, during the first and the second postpartum estrous cycles. Prior to and after calving, all cows were maintained in good body condition on Coastal bermudagrass pasture (IFN 1-00-703). The calves were allowed to suckle ad libitum, and sterile marker bulls were maintained with the cow herd as an aid in estrus detection throughout the trial. Cow weight and body condition score were recorded within 24 hours after calving and again at the first behavioral estrus observed. From day 1 through day 14 (day 0 = estrus) of both the first and the second postpartum estrous cycles, blood samples were collected from each cow, processed to yield serum and analyzed by radioimmunoassay for progesterone concentrations. There was a higher incidence of abnormal estrous cycles following the first postpartum estrus (35%) than following the second (5%) postpartum estrus (P<0.05). The abnormal first estrous cycles were characterized by either a short luteal phase (four cows) or by standing estrus behavior without luteal tissue formation (three cows). When serum progesterone concentrations were compared for all cows during the first estrous cycle with those during the second estrous cycle, there was less progesterone released during the cycle (P<0.05) and lower peak progesterone concentrations (P<0.10) during the first estrous cycle. However, if the abnormal cows were excluded from the analyses, there was no difference (P>0.10) in either progesterone concentrations through the 14 days measured or in peak progesterone concentrations between the first and the second postpartum estrous cycles. It can be concluded from this study that the higher incidence of abnormal luteal function following the first postpartum estrus may contribute to the decreased conception rates observed when cows are bred at their first postpartum estrus.     

Endocrine control of estrous cycle in mithun (Bos frontalis)

The objective of the present study was to establish the profiles of luteinising hormone (LH), follicle stimulating hormone (FSH), estradiol 17beta (E2) and progesterone (P4) secretion and their interrelationships during the natural estrous cycle of mithun (Bos frontalis). Daily blood samples were collected from second or third postpartum estrous cycles for determination of plasma concentrations of LH, FSH, E2 and P4. Concentration of P4 was found to be lowest on the day of estrus. It increased following estrus, attained the highest concentration on day 11 and decreased thereafter. Concentrations of LH and FSH varied significantly (p<0.01) during the first and last 6 days of the cycle and their variations were found to be synchronised. Both LH and FSH attained a biphasic peak during the estrous cycle. This biphasic peak lasted on from day -5 to day 3 of the cycle. The variations in maximum LH and FSH concentrations of both the phases did not differ significantly. During the entire estrous cycle, the E2 concentrations attained either one peak or two peaks. The first peak, approximately on day 4 before estrus was common in all animals. One additional peak was found on the day of estrus in 45% animals. A significant (p<0.01) negative relationship was found between P4 and, LH and FSH during the first and last 6 days of cycle. But a significant (p相似文献   

Intrauterine infusion of prostaglandin E2 and subsequent luteal function in cattle.

The objective was to evaluate the effect of intrauterine infusion of prostaglandin E2 (PGE2) on luteal function in cattle. Heifers and cows were randomly assigned after two normal estrous cycles to either PGE2 or control treatment groups. Females in Treatment A were infused with 1 mg of PGE2 once daily into the uterine horn ipsilateral to the corpus luteum between days 7-10 of the estrous cycle with a 0.25 ml plastic semen straw and an artificial insemination pipette. Females in Treatment B were similarly infused with 1 mg of PGE2 once daily in 20 ml of a carrier vehicle via a catheter on days 10 and 11 of the estrous cycle. Control animals were infused with the carrier vehicle using either a semen straw (Treatment C) or via a catheter (Treatment D) on the same days of the estrous cycle. Blood samples were collected daily to monitor plasma progesterone concentrations during the treatment period. Females infused with PGE2 on days 7-10 of the estrous cycle returned to estrus in a mean of 23.5 days (range 22-25 days) and were similar (P > 0.05) to those infused on days 10 and 11 which returned to estrus in 23.5 days (range 22-25 days). Animals similarly infused with carrier vehicle on the same days of the estrous cycle returned to standing estrus in 20.2 days (range 17-23 days). Plasma progesterone concentrations indicated an extended period of elevated progesterone concentrations in PGE2-treated animals compared with control animals. These results indicate that short term administration of PGE2 early in the estrous cycle may result in extended luteal maintenance.