The mRNA expression of the members of the IGF-system in bovine corpus luteum during induced luteolysis

The components of the IGF-system were shown to be differentially regulated in bovine antral follicles and corpora lutea (CL) during different stages of the estrous cycle, and to have important functions for specific stages. The aim of this study was to investigate the detailed pattern of mRNA expression of most constituents of the IGF-system and their possible involvement in prostaglandin (PG)F2alpha-induced luteolysis in the bovine CL. Therefore, cows in the mid-luteal phase (days 8-12) were injected with the PGF2alpha-analogue Cloprostenol, and CL were collected by transvaginal ovariectomy at 2, 4, 12, 48 and 64 h after PGF2alpha-injection. Real-time RT-PCR using SYBR Green I detection was employed to determine mRNA expressions of the following factors: ubiquitin (UBQ), insulin-like growth factor I (IGF I), IGF II, IGF-receptor type 1 (IGFR-1), growth hormone receptor (GH-R) and IGF-binding proteins-1-6 (IGFBP-1-6). Total extractable RNA decreased with ongoing luteolysis. IGFBP-1 mRNA was significantly up-regulated at 2h after PGF2alpha and maximal at 4h with a 34-fold increase. IGFBP-5 mRNA was significantly up-regulated after 12h with a maximum of an 11-fold increase at 64 h. For GH-R, IGFR-1, IGF II, IGFBP-3 and -4 mRNA expression, we found a significant down-regulation in certain stages. There was a significant up-regulation for IGFBP-2 and -6 mRNA at 64 h after induced luteolysis. There were no significant changes in IGF I mRNA expression. In conclusion, the IGF-system with all its components seems to play an important role in the very complex process of PGF2alpha-induced luteolysis in bovine CL.

Expression and localisation of oestrogen and progesterone receptors in the bovine mammary gland during development, function and involution

It is now well established that oestrogen and progesterone are absolutely essential for mammary gland development. Lactation can be induced in non-pregnant animals by sex steroid hormone treatment. Most of the genomic actions of oestrogens are mediated by two oestrogen receptors (ER)-alpha and ERbeta, and for gestagens in ruminants by the progesterone receptor (PR). Our aim was the evaluation of mRNA expression and protein (localisation and Western blotting) during mammogenesis, lactogenesis, galactopoiesis (early, middle and late) and involution (8, 24, 28, 96-108 h and 14-28 days after the end of milking) in the bovine mammary gland (total no. 53). During these stages, the mRNA was assessed by means of real-time RT-PCR (LightCycler). The protein for ERalpha, ERbeta and PR was localised by immunohistochemistry and Western blotting. The mRNA expression results indicated the existence of ERalpha, ERbeta and PR in bovine mammary gland. Both ERalpha and PR are expressed in fg/ micro g total RNA range. The highest mRNA expression was found for ERalpha and PR in the tIssue of non-pregnant heifers, followed by a significant decrease to a lower level at the time of lactogenesis with low concentrations remaining during lactation and the first 4 weeks of involution. In contrast, the expression of ERbeta was about 1000-fold lower (ag/ micro g total RNA) and showed no clear difference during the stages examined, with a significant increase only 2-4 weeks after the end of milking. Immunolocalisation for ERalpha revealed a strong positive staining in nuclei of lactocytes in non-pregnant heifers, became undetectable during pregnancy, lactogenesis and lactation, and was again detectable 14-28 days after the end of milking. In contrast, PR was localised in the nuclei of epithelial cells in the mammary tIssue of non-pregnant heifers, in primigravid animals, and during late lactation and involution. During lactogenesis, peak and mid lactation, fewer nuclei of epithelial cells were positive, but increased staining of the cytoplasm of epithelial cells was obvious. ERalpha and ERbeta protein was found in all mammary gland stages examined by Western blotting. In contrast to mRNA expression, the protein signal for ERalpha was weaker in the tIssue of non-pregnant heifers and during involution (4 weeks). ERbeta protein showed a stronger signal (two isoform bands) in non-pregnant heifers and 4 weeks after the end of milking. This correlated with the mRNA expression data. Three isoforms of PR (A, B and C) were found by Western blotting in the tIssue of non-pregnant heifers, but only isoform B remained during the following stages (lactogenesis, galactopoiesis and involution). In conclusion, the mRNA expression and protein data for ER and PR showed clear regulatory changes, suggesting involvement of these receptors in bovine mammary gland development and involution.

Effects of different sexual stimuli on oxytocin release, uterine activity and receptive behavior in estrous sows

This study was designed to assess effects of exogenous oxytocin (OT) on uterine activity, and to compare three different sexual stimuli in their effects on OT release, uterine activity and receptive behavior in estrous sows. Uterine activity was recorded nonsurgically, by transcervical insertion of an open-end catheter into the caudal part of the uterine lumen. After recording spontaneous uterine activity, exogenous OT was administered (Experiment 1), or one of the following stimuli was applied to the sow (Experiment 2): tactile stimuli, i.e. manual stimulation of the sow's back and flanks, tactile stimulation in combination with boar pheromone spray (5alpha-androstenon), or tactile stimuli in the presence of a boar. Both exogenous OT and endogenously released OT increased uterine activity. The effect depended on the uterine activity before treatment, with the effect being greater in those sows with lower uterine activity before treatment. In Experiment 2, boar presence was the only stimulus that elicited a clear, surge-like release of OT, and also clearly increased uterine activity. Release of OT was not necessary for induction of receptive behavior: tactile stimulation alone and in combination with pheromone spray elicited a standing response in one third of the sows, but had no effect on OT release.

Steroidogenesis during in vitro maturation of bovine cumulus oocyte complexes and possible effects of tri-butyltin on granulosa cells

Steroids are known as important factors on the route of oocytes development and cumulus oocyte complexes (COC) as well as follicular granulosa cells (GC) are suggested to be themselves involved in steroidogenesis. The aim of this study was to characterize such a local sex steroidogenic system during in vitro maturation (IVM) of bovine COCs according to the production of estradiol (E), testosterone (T) and progesterone (P). The expression of two steroid-converting key-enzymes was measured in parallel by quantitative RT-PCR. Furthermore, possible effects of the environmental pollutant tri-butyltin (TBT) were elucidated for the first time on bovine COC and GC in vitro concerning that steroidogenic system. During IVM of bovine COCs concentrations of P increased continuously, corresponding with steady-state levels of 3-beta-hydroxy-steroid-dehydrogenase (HSD) transcripts. In contrast, E together with P450 aromatase mRNA (ARO) increased in the first hours of IVM but declining thereafter, whereas T reached almost balanced levels. However, TBT showed only slight effects during IVM of COC. In cultured GC, LH caused highest P- and E-production within 24h and treatment with 50pM TBT induced a significant decrease of E in contrast to 100pM TBT and the control. These results indicate, that (1) COCs were able to modulate their steroidogenic environment in vitro and that (2) TBT may possibly influence or disturb steroidogenesis in the cows reproductive tract shown here for GC.

Investigations on the re-establishment of the positive feedback of oestradiol during anoestrus in the bitch

To test for the re-establishment of the positive feedback of oestradiol (E2) during anoestrus in the dog, the hypothalamo-pituitary-ovarian axis of five beagle bitches was challenged by treatments with oestradiol benzoate (EB), mimicking the course of the pro-oestric E2 secretion. Treatments in anoestrus started 7 days following the decline of progesterone (P) <1 ng/ml; they were repeated in 5 week intervals until onset of pro-oestrus; another treatment was performed during dioestrus 50 days after onset of the preceding pro-oestric bleeding. Each dog served as its own control by receiving vehicle-treatments in one of the following cycles. Each observation period covered a time window of 168 h and blood samples were collected for the determination of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and E2 in 6 (0-24 h) and 8 h (24-168 h) intervals. In the control periods and as indicated by the parameters area under curve (AUC), basal and maximal values, the availability of LH, FSH and E2 decreased from dioestrus to early anoestrus to increase again during the course of anoestrus (p < 0.05), indicating a gradual desensitization of the hypothalamus towards the negative feedback of oestradiol. At all times treatments with EB lowered the availability of FSH (decreased AUC and basal levels). A delay in the occurrence of the first LH peak after treatments with EB (p < 0.001) and decreased maximal values (p < 0.001) indicated a suppression of the LH-release. In no case treatment with EB led to a pre-ovulatory like LH-surge. In each dog the last trial with EB in anoestrus passed over into pro-oestrus/oestrus, with a reduced AUC and peak value of the pre-ovulatory LH-surge being the only differences to the control group. The observed differences in the response of LH and FSH to treatments with EB point towards subtle differences in the mechanisms controlling the release of these two hormones during anoestrus. From the data obtained, it may be concluded that the time window for E2 to act via a positive feedback seems to be very small and restricted to the end of anoestrus, and that full follicular function is a pre-requisite to allow for this phenomenon.

Steroids as local regulators of ovarian activity in domestic animals

The presented overview gives clear evidence for steroids as local regulators of follicular and luteal activity. In the follicle, estrogen receptor-alpha (ERalpha) and ERbeta expression are demonstrated in cow, ewe and pig. Besides species specific effects in general, there is evidence that estradiol-17beta (E(2)) exerts a dose-dependent inhibition on the secretion of progesterone (P(4)) by both theca interna cells (TI) and granulosa cells (GC). GC enhance the ability of the TI to produce androstendione by supplying them with progestin precursor. Androgen produced by TI enhances the ability of the GC to make E(2), and high concentrations of E(2) in the preovulatory follicle inhibit 3beta-HSD in both TI and GC and thus, may promote the use of the pathway Delta(5) for TI androgen production. The authors suggest that E(2) acts within the follicle to exert positive feedback on androgen and E(2) production, and exerts mitotic and anti-atretic or anti-apoptotic effects on follicular cells. Parts of the E(2)-mediated local action are regulated by stimulating effects on hormone receptors (LH, FSH, oxytocin). Gap junctions permit transfer of nutrients and cytokines to and from the avascular GC and oocyte, and formation is stimulated by estrogens. In bovine corpus luteum (CL) there is evidence that P(4) may directly regulate the production of P(4), oxytocin and prostaglandins (PGs) in a cycle dependent fashion. In most of domestic animal species, there is clear evidence for CL production of E(2) with clear stimulatory and luteotropic effects on P(4), and an intraluteal circuit that involves paracrine effects of E(2), oxytocin and PGF(2alpha) (especially in pigs). In contrast, there are species (ruminants, mares) in which the evidence for important local effects of E(2) is less clear, although expression of ERalpha, ERbeta and progesterone receptor (PR) is documented. Progesterone is very important for the regulation of CL lifetime by effects on the endometrium and release of the luteolytic signal PGF(2alpha). In conclusion, steroids as local regulators of ovarian activity are now documented and may stimulate further research in this field.

Expression and localization of IGF family members in bovine antral follicles during final growth and in luteal tissue during different stages of estrous cycle and pregnancy

The objectives of the study were to monitor the detailed pattern for mRNA expression (RT-PCR and RPA) of IGFs, IGFR-1, IGFBPs, GHR and localization of protein (immunohistochemistry) for IGF-1 and IGFR-1 in bovine follicle classes during final maturation and different corpus luteum (CL) stages during estrous cycle and during pregnancy. A relative high expression of IGF-1 in theca interna (TI) was observed before selection (E<0.5ng/mL). In GC, mRNA expression increased after selection. In contrast, IGF-2 was mainly expressed in the TI. The IGFR-1 mRNA was present in the TI and GC with increasing levels during final development. The expression results were confirmed by localization of IGF-1 and IGFR-1 proteins in GC and TI. There is clear evidence for the local expression of IGFBPs in TI and GC compartment with clear regulatory differences. In CL, the highest mRNA expression of IGF-1, IGF-2 and IGFR-1 was observed during early luteal phase, followed by a decrease, and then by a tendency of an increase during the mid and late luteal phases of the cyclic CL. This level remained low during pregnancy. Intense immunostaining for IGFR-1 in CL was observed mainly in large luteal cells. Evidence for a mRNA for all six IGFBPs were obtained with distinct differences for BP-3, -4 and -5. In conclusion, this comprehensive study gives clear evidence for an important role of the IGFs and IGFBPs in bovine follicular development and CL function. The relative amounts of IGFBPs may ultimately determine ovarian IGF action.

Estradiol-17beta is produced in bovine corpus luteum

The aim of this study was to investigate the expression of cytochrome P450 aromatase (aromatase) mRNA, its activity, and estradiol-17beta (estradiol) secretion in bovine corpus luteum (CL) during the estrous cycle. Expression of aromatase mRNA was examined in CL at the early, mid, late, and regressed luteal stages by using a reverse transcription-polymerase chain reaction. Aromatase mRNA was detected in all luteal stages examined, although aromatase expression was significantly lower during the early and regressed luteal phases compared to the mid and late luteal phases. Moreover, cultured midluteal cells clearly converted exogenous [(3)H]androstenedione into estradiol, and an aromatase inhibitor significantly inhibited this conversion. To characterize the local release of estradiol within the CL during the estrous cycle, an in vitro microdialysis system (MDS) of CL was conducted. Estradiol in MDS perfusate was confirmed by a reverse-phase high-performance liquid chromatography in combination with enzyme immunoassays. Basal release of estradiol from microdialyzed CL did not change during the estrous cycle. Additionally, when freshly prepared midluteal cells were exposed to estradiol (10(-14) to 10(-9) M), estradiol stimulated prostaglandin (PG) F(2alpha) secretion (P < 0.05), although it did not affect progesterone and oxytocin secretion. The overall results indicate that estradiol is produced locally in bovine CL throughout the estrous cycle, and they suggest that estradiol plays a role in regulating PGF(2alpha) production in CL as an autocrine/paracrine factor.

Inhibition of oxytocin release and milk let-down in postpartum primiparous cows is not abolished by naloxone

About 10% of primiparous cows have no milk ejection during the first milkings after delivery. Therefore, 17 Brown Swiss dairy cows in their first lactation were used to evaluate the extent of disturbed milk let-down and the corresponding oxytocin (OT) plasma values in the 1st 5 days after delivery. The first milking was 9-22 h after parturition and served for classification of the cows to groups with inhibited (INH), bimodal (BIMO), or normal (NOR) milk let-down. The OT plasma levels before the start of manual teat stimulation and machine milking were comparably high during the first milking especially in NOR and BIMO cows. Ten minutes before the second milking (M2), 300 mg of the opioid antagonist naloxone was injected to test whether the disturbance was affected by the action of endogenous opioids on the neurohypophysis. The milk yield was not influenced by the naloxone treatment, and the INH cows had milk ejection only after a vaginal stimulation. Afterwards, the cows were milked twice every day, until the milk let-down and the OT release were unaffected (equal to control milking). Then, at the next milking, the cows were injected with 300 mg morphine 10 min before milking. The central OT release in response to manual teat stimulation and machine milking was completely blocked in all cows, but a vaginal stimulation was able to abolish this block, at least partially, in 16 cows. Thus, morphine produced a milk let-down characteristic as in the INH cows during the first three milkings. For the following milking, the cows were pre-treated with 300 mg naloxone (-15 min) plus 300 mg morphine (-10 min) before milking. The OT release and the milk yields were unaffected when compared with the control milking. This experiment demonstrates that exogenous opioids can affect the central release of OT in a naloxone-reversible manner even very soon after parturition. However, endogenous opioids are probably not the main mediators of disturbed central OT release and alveolar milk ejection in post-partum primiparous cows.

Stimulatory and synergistic effects of luteinising hormone and insulin like growth factor 1 on the secretion of vascular endothelial growth factor and progesterone of cultured bovine granulosa cells

Vascular endothelial growth factor (VEGF) is the most important factor in the regulation of angiogenesis. Associated with luteinisation and formation of corpus luteum (CL) are alterations in luteal vascularity. The aim of the study was to test under in vitro conditions the stimulation of VEGF and progesterone (P) secretion of bovine granulosa cells by LH, IGF1 (insulin like growth factor) or by factors known to be produced by luteinised granulosa cells or in the early CL. Localisation of VEGF protein in preovulatory follicle and early CL were achieved by immunohistochemistry. LH and IGF1 stimulated dose dependently and significantly P and VEGF when tested alone. Both hormones added simultaneously had clear additive and even more interesting far greater (synergistic) effects on P with LH (0.1 ng/ml) plus 5 or 10 ng IGF1. In contrast, VEGF was stimulated only additively with 0.1 ng/ml of LH plus 5 or 10 ng IGF1. But with the higher dose of LH (1 ng/ml) additionally to the additive effect a tendency for a synergistic action (which was significant with 1 ng LH plus 5 ng IGF1/ml) was observed. Endothelin, oxytocin, progesterone, atrial natiuretic peptide, angiotensin II, prostaglandin F2 alpha alpha, prostaglandin E2, cortisol, fibroblast growth factor 1 and 2 and growth hormone showed no effect neither on P nor on VEGF. Tumour necrosis factor alpha (TNF alpha) stimulated (P < 0.05) VEGF with 10 or 100 ng/ml but not P. TPA (12-0 tetra decaenoyl-phorbol-13-acetate) or Ca2+ ionophore did not show a stimulatory effect in contrast to forskolin which increased P and VEGF secretion dose dependently. The VEGF protein was localised in follicle (granulosa cells, theca cells and some endothelial cells) and early (about 24 h after ovulation) CL (granulosa-lutein cells and endothelial cells). The same signalling pathway by stimulation of cAMP production and proteinkinase A activation for luteinisation and neo-vascularisation demonstrates a close temporal and spatial relationship of these normal physiological processes.

Uterine responses to exogenous oxytocin before and after pre-partum luteolysis in the cow

The aim of this study was to test the functional status of uterine oxytocin receptors in cows in vivo around parturition. The animals received consecutive, intra-arterial injections of 800, 1,600 and 3,200 mU of oxytocin at three different stages: during late gestation (days 260-274), at 12 h and at 24 h after intramuscular injection of a prostaglandin F2alpha analogue at day 275 to induce parturition. Cows (n = 6) had been provided with myometrial electrodes and a catheter had been installed in the aorta and in a branch of the uterine vein (UV). Regular blood samples were obtained from the UV from 5 min before until 45 min after each oxytocin injection to measure plasma levels of prostaglandin F2alpha (PGF2alpha) and oxytocin. Uterine electromyographic (EMG) activity was registered continuously during each experiment. The increase of oxytocin levels in UV plasma after intra-arterial injections was dose dependent (p < 0.02). Pre- and post treatment oxytocin levels at 24 h after induction of parturition were significantly increased (p = 0.0313). Both during late pregnancy and at 12 h after induction of parturition, oxytocin caused a significant increase in EMG activity (p = 0.022). After the 3,200 mU dose the increase was significantly higher than with the other 2 doses (p = 0.004). After each dose, EMG activity returned to baseline levels within some 15 min. At 24 h after induction of parturition, the pre-treatment level of EMG activity had increased. Doses of 800 mU and 1,600 mU of oxytocin produced a significant (p = 0.022) increment of EMG activity, which was of the same magnitude as during the preceding stages; after 3,200 mU of oxytocin the response was significantly higher than before (p = 0.008). No significant increases of PGF2alpha levels in UV plasma could be measured after oxytocin injections at any of the three stages. It is concluded that the myometrium of the pregnant cow responds in vivo to physiological doses of oxytocin. At 24 h after induction of parturition, when luteolysis has occurred and a parturient pattern of parturient myometrial activity has already started to develop, the response is enhanced. Physiological doses of oxytocin did not evoke a spurt release of PGF2alpha in uterine venous blood during the peripartal period.

Production and localisation of angiotensin II in the bovine early corpus luteum: a possible interaction with luteal angiogenic factors and prostaglandin F2 alpha

The newly formed corpus luteum (CL) rapidly develops after ovulation and has the features of active vascularisation and mitosis of steroidogenic cells. These stage-specific mechanisms also may contribute to gain the function of prostaglandin F2 alpha (PGF2 alpha)-resistant CL at this stage. Recent studies suggest that the vasoactive peptide angiotensin II (Ang II) regulates luteal function. Thus, this study aimed to investigate (i) the expression of angiotensin-converting enzyme (ACE) mRNA by RT-PCR and the ACE protein expression by immunohistochemistry, (ii) the effects of angiogenic growth factors, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), on the secretion of Ang II, PGF2 alpha, progesterone and oxytocin (OT), and (iii) the effects of luteal vasoactive peptides (Ang II and endothelin-1 (ET-1)) or OT on the secretion of PGF2 alpha, progesterone and OT from bovine early CL (days 3--4 of the oestrous cycle), and evaluate a possible interaction of these substances with PGF2 alpha. The expression of mRNA for ACE was found in theca interna of mature follicle, early CL and endothelial cells from developing CL as well as pituitary and kidney, but granulosa cells of mature follicle were negative. The immunohistochemical analysis revealed that blood capillaries (endothelial cells) were stained for ACE, but luteal cells were negative in early CL. To examine the effects of substances on the secretory function of the CL, an in vitro microdialysis system was used as a model. The infusion of bFGF and VEGF stimulated Ang II and PGF2 alpha secretion as well as progesterone, but not OT secretion in early CL. The infusion of Ang II after PGF2 alpha infusion continued the stimulatory effect on progesterone and OT release within early CL until 3 h thereafter. However, the infusion of ET-1 alone had no effect on progesterone or OT release. The infusion of luteal peptides such as Ang II and OT stimulated PGF2 alpha secretion, whereas the infusion of ET-1 did not. In conclusion, the overall results of this study indicate that a functional angiotensin system exists on the endothelial cells of early CL, and that angiogenic factors bFGF and VEGF upregulate luteal Ang II and PGF2 alpha secretion, which fundamentally supports the mechanism of progesterone secretion in bovine early CL. This idea supports the concept that the local regulatory mechanism involved in active angiogenesis ensures the progesterone secretion in the developing CL in vivo.

The effects of conditioning to suckling, milking and of calf presence on the release of oxytocin in dairy cows

The aim of the study was to record the oxytocin (OT) release during milking (M) without or with calf presence, suckling (S) and finally calf removal just before the next milking in cows during postpartum or early lactation periods. Furthermore, the release of OT was examined during S and M in unknown surroundings (parlour). A total of 20 Brown Swiss cows kept under loose housing environment were used in our experiment. In both periods, the cows were milked twice daily at 07.00 and 18.00h and suckled three times daily at 09.00, 14.00 and 20.00h in the stall (tie housing). In the postpartum period, 13 cows were suckled and milked in the presence of their calves in the stall for the first 5 days of postpartum. Five from seven primiparous cows were additionally suckled by their own calves in the parlour on day 5 at 20.00h. On day 6, calves were separated and moved from mothers to the calf barn 10min before morning M. After evening milking cows were relocated to the herd within the same stable and milked in the parlour for a period of 4 weeks without contact to their calf. For control, additional seven primiparous cows without calf presence (not suckled) were also milked in the tie housing. In the early lactation period, suckled cows were moved back to the tie housing 2 days before the start of two consecutive days of S by their own calves and milking. Afterwards, 10min before M calves were separated again. Before S, two consecutive M were considered as controls. Results: The S stimulus during postpartum resulted in a higher OT release as compared with M in the calf presence and M after calf separation but not during M of not suckled cows. S in parlour reduced OT release. However, when not suckled primiparous cows were first milked in parlour, OT release was more reduced and in some cows total inhibition was observed. In early lactation during the first S, release of OT was lower than during control M, but increased gradually with repeated S and reached a maximum already on the second day. After two S, during evening M, the M related OT release was reduced as compared with controls. Calf removal 10min before M reduced OT release as compared with control M or M in calf presence. In conclusion, the calf presence and its removal can negatively influence OT secretion during M. Conditioning to machine milking caused a short-term reduction of OT release during first suckling, which normalised within 1 day.

Naloxone cannot abolish the lack of oxytocin release during unexperienced suckling of dairy cows

To evaluate the role of opioids for the regulation of oxytocin release in response to teat stimulation, 10 brown-Swiss dairy cows were randomized to two experiments during mid of lactation. In the first experiment, four cows without previous suckling experience were suckled by an alien calf between two normal milkings. Before and during milking or suckling, frequent blood samples were collected via a jugular cannula for determination of oxytocin and beta-endorphin. In the second experiment, six cows were treated with naloxone or saline, 10min before the start of the first or second suckling, respectively. The collected blood samples were assayed for oxytocin.In the first experiment, the plasma levels of beta-endorphin were elevated during and after the unexperienced suckling in three cows, but not in the fourth cow, and the release of oxytocin during suckling was markedly reduced, suggesting no release of alveolar milk. In the second experiment, the release of oxytocin during suckling was again significantly reduced. Pretreatment with naloxone before suckling did not completely abolish the adverse effect of suckling and the oxytocin plasma level did not increase to levels comparable with control milking.In emotional stress situations, the release of oxytocin from the pituitary is inhibited with simultaneously elevated beta-endorphin plasma levels. Although there is some evidence for a regulatory role of opioids for the release of oxytocin, other mediators are suggested to be more potent in regulating oxytocin under stress conditions.

Expression and localization of growth factors during mammary gland development

Growth and differentiation of the mammary gland during development and lactation are controlled by complex hormonal mechanisms. Additionally growth factors are supposed to act as local mediators of the hormonally controlled developmental processes. Mammary tissue for this study was obtained from non pregnant control heifers, primigravid heifers (second part of pregnancy), around parturition, during lactation (early and late) and from dry cows. Using RT-PCR and ribonuclease protections assay (RPA) the expression of the following growth factors was studied in the different phases bovine mammary gland development: Insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), fibroblast growth factor 1 (FGF-I), fibroblast growth factor 2 (FGF-2), transforming growth factor alpha (TGF-alpha). Additionally the expression of fibroblast growth factor receptor (FGFR) and growth hormone receptor (GHR) was investigated. The cellular distribution pattern of several of these growth factors and GHR was obtained using Immunocytochemical techniques. The detailed expression and localization pattern of these growth factors are presented and their role in the local regulation of the bovine mammary gland is briefly discussed.

The expression of the IGF family and GH receptor in the bovine mammary gland

To study the involvement of the IGFs in mammary development and lactation of the cow, the temporal expressions of IGF-I and -II, its receptor type 1 (IGFR-1), IGF-binding proteins (IGFBPs)-1 to -6 and GH receptor (GHR) mRNA were examined. This was carried out for different stages of mammogenesis, lactogenesis, galactopoiesis and involution in the bovine mammary gland of 26 animals. Furthermore, IGF-I was localised by immunohistochemistry. The highest mRNA concentrations for IGF-I were detected in the mammary tissue of late pregnant heifers (days 255-272) and significantly lower expression was detected during lactogenesis and galactopoiesis. Immunohistochemistry of IGF-I revealed only a weak staining in the epithelium of the ducts during mammogenesis. The epithelium of the alveoli were negative during mammogenesis, lactogenesis and galactopoiesis but displayed distinct IGF-I activity during involution. In the stroma a distinct staining of the cytoplasm of adipocytes and of vascular smooth muscle cells was observed. A certain percentage of fibroblasts (usually 20-30%) were also immunopositive. In contrast, highest expression for IGFR-1 was detected during galactopoiesis and involution. The lowest mRNA concentration for IGFR-1 was found during pregnancy (days 194-213). In general, the expression of IGF-II was not regulated during mammogenesis and lactation, but decreased during involution. The mRNA for the six binding proteins was detected in the bovine mammary gland. The dominant binding proteins were IGFBP-3 and -5. The highest expression of IGFBP-3 was observed during mid-pregnancy and the lowest during late lactation, involution and in non-pregnant heifers. The mRNA for IGFBP-5 increased during late mammogenesis and lactogenesis followed by a decrease thereafter. In general, the mRNA concentrations for IGFBP-2, -4 and -6 were barely detectable during all stages. In contrast, the expression for IGFBP-1 was upregulated in the mammary gland of virgin heifers and increased around the onset of lactation. mRNA for GHR was found during all stages examined without outstanding fluctuations. In conclusion, locally produced IGF-I and -II may mediate mammogenesis. The high mammary IGFR-1 mRNA during lactation suggests a role for peripheral IGF-I in maintenance of lactation. The role of IGFBPs in the mammary gland needs further evaluation.

Growth hormone, but not luteinizing hormone, acts with luteal peptides on prostaglandin F2alpha and progesterone secretion by bovine corpora lutea in vitro

Prostaglandin F2alpha (PGF2alpha) is a major physiological luteolysin in the cow. However, injection of PGF2alpha before day 5 (day 0 = estrus) of the estrous cycle dose not induce luteolysis. On the other hand, the early corpus luteum (CL) actively produces PGF2alpha. This indicates that luteal PGF2alpha may play a key role in the refractoriness to PGF2alpha injected during the early luteal phase when angiogenesis is active in the CL. Thus, this study aimed to investigate the possible interaction between pituitary hormones and local factors (luteal peptides) on secretion of PGF2alpha and progesterone (P) by the early bovine CL, and to evaluate the effect of growth hormone (GH) as well as its interactions on production of PGF2alpha in the developing CL. A RT-PCR analysis revealed that mRNA for GH receptor in CL was fully expressed from early in the luteal phase throughout the estrous cycle, while luteinizing hormone (LH) receptor mRNA was expressed less by the early and regressing CL than those at mid or late luteal phases (P < 0.05). For the stimulation test, an in vitro microdialysis system (MDS) was used as a model. Each bovine early CL (days 3-4) was implanted with the MDS, and maintained in an organ culture chamber. The infusion of GH, insulin-like growth factor-I (IGF-I) and oxytocin (OT) increased (P < 0.05) PGF2alpha and P release. In contrast, LH had no effect (P > 0.05) on PGF2alpha secretion and little effect on P release. Unexpectedly, there was no distinct interaction between pituitary hormones and luteal peptides on secretion of PGF2alpha and P. These results indicate that GH is a more powerful stimulator of PGF2alpha and P production in the early bovine CL than LH and suggest that GH and luteal peptides, IGF-1 and OT, contribute to maintenance of elevated PGF2alpha production in the developing bovine CL.

Expression and localisation of vascular endothelial growth factor and basic fibroblast growth factor during the final growth of bovine ovarian follicles

Locally produced growth factors may have important modulatory roles in final ovarian follicular growth. The aim of this study was to investigate the possible participation of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF2) in bovine follicles during final growth. Ovaries were collected from a slaughterhouse within 10-20 min after exsanguination. A classification of follicles into five groups (<0.5; >0.5-5; >5-20; >20-180; >180 ng/ml) was performed according to the follicular fluid (FF) oestradiol-17 beta content. For a better characterisation of classes the mRNA expressions of FSH receptor, LH receptor and aromatase cytochrome P450 in theca interna (TI) and granulosa cells (GC) were determined. Analysis of VEGF transcript by RT-PCR showed that GC and theca cells express predominantly the smallest isoforms (VEGF(121) and VEGF(165)). VEGF mRNA expression in both tissues (TI and GC) and VEGF protein concentration in total follicle tissue increased significantly (and correlated) with developmental stages of follicle growth. The expression of mRNA for VEGF receptor (VEGFR)-1 and VEGFR-2 was very weak in GC, without any regulatory change during final follicle growth. In contrast, TI showed strong expression of mRNA for both receptors in all follicle classes examined. VEGF protein concentrations in FF increased significantly and continuously to maximum levels in preovulatory follicles. As shown by immunohistochemistry, VEGF protein was clearly localised in TI and GC of preovulatory follicles. FGF2 and FGF receptor (FGFR) mRNA expression in TI increased significantly during final growth of follicles. In contrast, the FGF2 and FGFR mRNA expression in GC was very weak and without any regulatory change during follicle growth. Histological observation revealed that FGF2 protein was localised in theca tissue (cytoplasm of endothelial cells and pericytes) but not in GC. Our results suggest that VEGF and FGF families are involved in the proliferation of capillaries that accompanies the selection of the preovulatory follicle resulting in an increased supply of nutrients and precursors, and therefore supporting the growth of the dominant follicle.

Cortisol and ACTH release in dairy cows in response to machine milking after pretreatment with morphine and naloxone

The aim ot the study was to examine the effect of morphine and naloxone pretreatment on cortisol and ACTH concentrations in response to machine milking in dairy cows. In the first part of the experiment, the effects of i.v. morphine doses (0, 21, 70 and 210 mg, one dose each day) 10 min before morning milking were studied in six Brown Swiss dairy cows. In the second part, four cows were treated 1 d after the control milking with 210 mg morphine at 10 mm before milking and the next day with 210 mg naloxone at 15 min before milking followed by 210 mg morphine at 10 min before milking. In addition, four other cows were treated 1 d after the control milking with 210 mg naloxone at 10 min before milking. Pretreatment with morphine significantly suppressed the machine milking-induced increase of cortisol in blood plasma as compared with controls. Naloxone pretreatment overcame the inhibitory effect of morphine and elevated milking-induced cortisol concentrations. Naloxone administration alone significantly increased cortisol concentration resulting from milking as compared with controls. However, ACTH concentrations did not change in either control or treated animals, suggesting an ACTH-independent release mechanism for cortisol during milking. We conclude that the release of cortisol in response to machine milking seems to be modulated by emidogenous opioids at the adrenal level and does not appear to be under the control of ACTH.

Periovulatory changes in the local release of vasoactive peptides, prostaglandin f(2alpha), and steroid hormones from bovine mature follicles in vivo

We previously proposed that an endothelin-angiotensin-atrial natriuretic peptide system may contribute to inducing ovulation of mature bovine follicles by modulating follicular secretion of steroids and prostaglandins (PGs). Thus, this study aimed to determine the real-time changes in the local release of angiotensin II (Ang II), endothelin (ET), atrial natriuretic peptide (ANP), PGF(2alpha), and steroid hormones from bovine mature follicles during the periovulatory period in vivo. Seven cows were treated for superovulation using FSH and PGF(2alpha) injections. Two dialysis capillary membranes per follicle were surgically implanted into the theca layer of mature follicles and connected to a microdialysis system (MDS). Fractions of the perfusate were collected from Day -1 (Day 0 = LH surge) to Day 3. Five out of seven treated cows were normally ovulated, and the newly formed corpora lutea were observed at the end of the experiment. In these five ovulated cows, the release of estradiol, androstenedione, and progesterone in the theca layer increased (P < 0.05) synchronously with the LH surge. Acute increases in PGF(2alpha) and Ang II concentrations in the ovarian venous plasma (OVP) were observed at 24-48 h after the peak of the LH surge, when multiple ovulations were expected to occur. The follicular Ang II release was low during the pre-LH surge period and rose (P < 0.05) at the beginning of the increase in the LH surge. On the other hand, ET-1 release dropped (P < 0.05) when plasma LH started to increase. However, no clear changes in ANP concentration in the MDS perfusate and plasma were observed. The above local changes in Ang II, PGF(2alpha), as well as steroid hormones were not observed in cows (n = 2) that did not show an LH surge and ovulation. The present results demonstrate for the first time the local release of Ang II, ET-1, and ANP from the bovine mature follicle in real-time in vivo and show that Ang II and PGF(2alpha) concentrations in the OVP acutely increase around the time of ovulation. The overall results support the concept of a local functional ET-Ang-ANP system in the bovine mature follicle that may be involved in the ovulatory process.

Expression and tissue concentration of vascular endothelial growth factor, its receptors, and localization in the bovine corpus luteum during estrous cycle and pregnancy

The presence of vascular endothelial growth factor (VEGF) in the ovary has been reported in a number of species. The objective of the present study was to demonstrate the expression of VEGF, VEGF receptor (R)-1, and VEGFR-2 in detail by different methodological approaches in bovine corpora lutea (CL) obtained from different stages of the estrous cycle and during pregnancy. VEGF and VEGF receptor transcripts were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and ribonuclease protection assay. All components of the VEGF system were found in the bovine CL during the estrous cycle and pregnancy. Analysis of VEGF transcript by RT-PCR shows that CL tissues expressed predominantly the smallest isoforms (VEGF(121) and VEGF(165)). The highest mRNA expression for VEGF and VEGFR-2 mRNA was detected during the early luteal phase, followed by a significant decrease of expression during the mid and late luteal phase and a further decrease of VEGF mRNA after regression. During pregnancy, high levels of expression were always present. In contrast, no significant change in VEGFR-1 mRNA expression during the estrous cycle and pregnancy was found. The VEGF protein concentration in CL tissue was significantly higher (20.9-23.4 ng/g wet weight) during the early luteal phase (Days 1-7), followed by a decrease at the late luteal phase (14.3-18.7 ng/g wet weight) and, especially, after CL regression (2.8 ng/g wet weight). However, relatively high levels were found during pregnancy (10.1 ng/g wet weight). As achieved by immunohistochemistry, VEGF protein was localized predominantly in luteal cells. High VEGF protein and transcript concentrations and increased VEGFR-2 expression during the early luteal phase coincided with luteal vascularization. These results suggest an important role of VEGF in angiogenesis of the newly formed CL. The high VEGF mRNA expression and protein levels during matured vasculature in the mid-stage CL and pregnancy also suggest also a survival function for endothelial cells.

Cellular localisation of GH receptor in the bovine mammary gland during mammogenesis, lactation and involution

We have used immunohistochemistry and non-radioactive in situ hybridisation to localise the GH receptor and its transcript in the bovine mammary gland during mammogenesis, lactation and involution. We found a characteristic pattern of immunoreactive GH (irGH) receptor distribution in the epithelial and stromal compartments during the different stages of mammary gland development: The ductular epithelium showed a distinct staining for irGH receptor during most stages, whereas the alveolar epithelium contained a modest amount of GH receptor during pregnancy which increased during lactation and galactopoiesis. In dry cows, the immunostaining for GH receptors in the alveolar epithelium was very weak or negative. Curiously, the amount of GH receptor mRNA appeared relatively constant during mammogenesis and lactation. The epithelial cells of the alveoli and ducts as well as the endothelial cells showed a distinct signal in our in situ hy! bridisation studies. The predominant localisation of GH receptors in the epithelium of ducts and alveoli is supportive of a role for GH in epithelial differentiation and maintenance. Furthermore, the increased intensity of immunostaining in bovine mammary tissue post partum suggests a direct role for GH receptor in mediating the effect of GH in milk production and secretion.

Cellular localization of fibroblast growth factor 2 (FGF-2) in benign prostatic hyperplasia

Fibroblast growth factor 2 (FGF-2, basic fibroblast growth factor) has been reported to be elevated in tissues from benign prostatic hyperplasia (BPH), the most frequent neoplastic disease in aging men. This suggests that FGF-2 may play a significant role in the development of BPH. In this study the cellular distribution pattern of FGF-2 in tissues from BPH has been investigated by immunohistochemical and molecular biological methods. Radioimmunoassay revealed high concentrations of FGF-2, ranging between 450 and 950 ng per g tissue. Immunoblots confirmed the presence of a 18 kDa FGF-2 in tissue extracts. By immunohistochemistry done with a polyclonal antibody to recombinant FGF-2 on paraffin sections, FGF-2 was localized in fibroblasts, endothelial cells and smooth muscle cells of tissue samples of BPH. Nuclei of these cells were labelled distinctly. Moreover the cytoplasm of smooth muscle cells was labelled moderately. No immunostaining was seen in prostatic epithelium. Non-radioactive in situ hybridization with digoxygenin-labelled oligonucleotides revealed the presence of mRNA for FGF-2 in smooth muscle cells of the prostatic stroma. These results provide evidence that FGF-2 may be produced locally in the human prostate as a stroma-specific mitogen and may play a causal role in the development of BPH.

Growth factors and extracellular matrix proteins in interactions of cumulus-oocyte complex, spermatozoa and oviduct

The expression and localization of selected growth factor systems and extracellular matrix (ECM) components that may influence oocyte maturation and fertilization within the mammalian oviduct are reported. Fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) systems could be detected by use of RT-PCR, RNase protection assay (RPA) and immunohistochemistry in bovine follicles, bovine cumulus-oocyte complexes (COC) and bovine and marmoset oviducts. Two different subtypes of the FGF receptor (FGFR-1 and -2) were identified in distinct cell types, indicating a functional difference. A complete epidermal growth factor (EGF) system was found in the porcine, but not in the bovine, oviduct. There were additional differences between bovine and primate oviducts: FGF-1/2 and FGFR were increased in the marmoset around ovulation, in contrast to an increase in FGF-1 in the cow. Immunohistochemistry revealed accumulation and storage of FGF and VEGF on the surface of the epithelium, possibly due to their binding property on heparanglycoproteins. Other ECM components, matrix metalloproteinase 1 (MMP-1) and tissue inhibitor of metalloproteinase 1 (TIMP-1), were found to be modulated in the ovarian follicle, COC and oviduct during the cycle. An oviduct-mediated depletion of sperm surface proteins (BSP1-3) was discovered as well as a sperm-induced novel oviductal mRNA related to an anti-oxidant protein family. Associated systems of growth factors and ECM components can be suggested as paracrine or autocrine mediators during fertilization in a species-, cycle- and tissue-dependent manner.