Local increase of steroid hormone concentrations in blood supplying the uterus and oviduct in anaesthetized and conscious gilts

Progesterone-Induced Sperm Release from the Oviduct Sperm Reservoir

In mammalian females, after sperm are deposited in the reproductive tract, a fraction of sperm migrates to the lower oviduct (isthmus) and forms a sperm storage site known as the functional sperm reservoir. The interactions between sperm membrane proteins and oviduct epithelial cells facilitate sperm binding to the oviductal epithelium and retention in the reservoir. Sperm are bound by glycans that contain specific motifs present on isthmic epithelial cells. Capacitated sperm are released from the reservoir and travel further in the oviduct to the ampulla where fertilization occurs. For decades, researchers have been studying the molecules and mechanisms of sperm release from the oviductal sperm reservoir. However, it is still not clear if the release of sperm is triggered by changes in sperm, oviduct cells, oviduct fluid, or a combination of these. While there is a possibility that more than one of these events are involved in the release of sperm from the reservoir, one activator of sperm release has the largest accumulation of supporting evidence. This mechanism involves the steroid hormone, progesterone, as a signal that induces the release of sperm from the reservoir. This review gathers and synthesizes evidence for the role of progesterone in inducing sperm release from the oviduct functional sperm reservoir.

Expression of hypoxia inducible factor 1α and antioxidant enzymes: Superoxide dismutases-1 and -2 in ischemic porcine endometrium

The aim of this study was to determine how 60-min ischemia changes the expression of hypoxia inducible factor 1α (HIF-1α) and superoxide dismutases (SOD)-1 and -2 in selected regions of porcine uterine horns. The results showed that 60-min ischemia of the porcine uterus conducted at the mid-secretory estrous phase caused decreased HIF-1α and increased SOD-2 gene expression. Higher expression of SOD-2 suggests that this enzyme may play an important role in the suppression of HIF-1α accumulation in an ischemic endometrium.

Contractile effect of PGF2alpha and PGE2 on isolated branches of uterine and ovarian artery in different days of estrous cycle and early pregnancy in pigs

The contractile effects of PGF2alpha (3 x 10(-6) to 10(-4) M) and PGE2 (10(-7) to 10(-5) M) were examined on isolated branches of ovarian artery (OA) and extramyometrial branches of uterine artery (UA) collected from pigs in the luteal (day 10-12) and follicular phase (day 17-20) of the estrous cycle, and during early pregnancy (day 10-12). Strong contraction was demonstrated in both arteries during all investigated periods in response to PGF2alpha, which was significantly higher (P < 0.01) than to PGE2, being negligible in the follicular phase. In UA, the effective dose of PGF2alpha (ED50) amounted 7.9 x 10(-6) M and 6.3 x 10(-6) M in the luteal and follicular phase, and 5.0 x 10(-6) M in early pregnancy. ED50 for PGE2 reached 5.0 x 10(-7) M in the luteal phase, and 4.1 x 10(-7) M in early pregnancy. For both prostaglandins, the contraction was much stronger (P < 0.01) in OA than in UA branches. In OA, the ED50 for PGF2alpha was 1.2 x 10(-5) M in the luteal phase and was significantly higher (P < 0.05) than in the follicular phase (3.1 x 10(-6) M) and early pregnancy (2.7 x 10(-6) M). ED50 for PGE2 amounted 7.3 x 10(-7) M in the luteal phase and 1.7 x 10(-7) M in early pregnancy. Studies showed the influence of the estrous cycle and early pregnancy on OA branches sensitivity to the contractile effect of PGF2alpha and the lack of this effect on UA branches, and the influence of the estrous cycle on UA and OA branch contraction in response to PGE2.

The effect of unilateral progesterone infusion into the ovarian artery during the middle luteal phase on progesterone secretion in gilts

The aim of the study was to determine, in an experiment performed on conscious gilts, whether an increased amount of progesterone (P4) supplied to the porcine corpus luteum (CL), maintained within a physiological systemic concentration would influence its own secretion. On day 9 of the estrous cycle the jugular veins as well as both ovarian arteries and both ovarian veins were cannulated. In the experimental gilts (n=5), P4 was infused into the right ovarian arteries on days 10, 11 and 12 of the estrous cycle at a rate adequate for physiological retrograde transfer found during the middle luteal phase. The left ovarian arteries of these gilts were infused with saline. Both ovarian arteries of the control gilts (n=5) were infused with saline. The P4 infusion rate was 0.62 microg/min (10 day), 2 x 0.62 microg/min ( 11 day) and 3 x 0.62 microg/min (12 day) and physiological levels of the steroid were maintained. Blood samples were collected from the jugular vein and both ovarian veins in the experimental and control animals on days 10, 11 and 12 of the estrous cycle during two periods on each day: before and after P4 or saline infusion. The mean plasma P4 level in the ovarian vein ipsilateral to the P4-infused ovary was significantly (p<0.001) higher on days 10-12 of the estrous cycle than those found in contralateral ovarian vein of the experimental gilts and in the ovarian vein of the control gilts. This was also true for day 12 of the estrous cycle (p<0.001). However, on days 10 and 11 plasma P4 in the vein from the P4-infused ovary tended (p<0.061) to be higher than those in veins from the saline-treated ovaries. The mean P4 concentration in the ovarian vein ipsilateral to the P4-infused ovary did not vary significantly (p>0.05) among the particular days of the experiment. In contrast, mean P4 levels in the contralateral ovarian vein of the experimental gilts as well as in the ovarian vein of the control gilts tended to decrease (p<0.06) between day 10 and day 12. The results of the present paper indicate that during the middle luteal phase of the porcine estrous cycle (days 10-12), ovarian P4 secretion remained unaltered due to the elevation of P4 concentration in blood supplying the steroid-infused ovary, while a decrease in P4 concentration was observed in ovarian veins of the saline-infused ovaries. The influence of the progestagen on its own secretion suggests that on days 10-12 of the porcine estrous cycle there is a short regulatory loop of positive feedback between P4 being retrograde transferred into the ovary and P4 ovarian secretion.

The role of the endometrium in endocrine regulation of the animal oestrous cycle

A critical analysis of the results of research in the function of the endometrium was carried out and a view point presented. The role of the endometrium in endocrine regulation of the oestrus cycle can be summarized as follows: 1. The transfer of prostaglandin F(2alpha) (PGF(2alpha)) from the uterus to an ovary, which causes luteolysis, occurs mainly via the lymphatic pathways. 2. The system of retrograde transfer of PGs enables PGF(2alpha) and PGE(2) to reach the myometrium and endometrium with arterial blood at high concentration. In the luteal phase, PGF(2alpha), together with the increasing concentration of progesterone, constricts the arterial vessels of the uterus; in the follicular phase and in early pregnancy, PGE(2) together with oestrogen and embryonic signals, relaxes the arterial vessels. In addition, this system protects the corpus luteum from premature luteolysis during the cycle and luteolysis during early pregnancy. 3. In days 10-12 of the cycle, the blood flow in the uterus decreases by 60-70% in pigs and around 90% in sheep. This causes ischaemia and local hypoxia confirmed by the presence of hypoxia inducible factor and thus remodelling of the endometrium commences. 4. The pulsatile elevations in PGF(2alpha) concentration occurring in the blood flowing out of the uterus during the period of luteolysis and the next few days, do not result from increased PGF(2alpha) synthesis as suggested in numerous studies. They are the effect of excretion of PGF(2alpha) and its metabolites together with lymph and venous blood and tissue fluids in which prostaglandin accumulates.

Retrograde and local destination transfer of uterine prostaglandin E2 in early pregnant sow and its physiological consequences

The local destination transfer of prostaglandin E2 (PGE2) from the uterine lymph to arterial blood supplying the ovary and its retrograde transfer to arterial blood supplying the uterine horn and the effect of additional delivery of PGE2 into the ovary on the secretion of steroid hormones was studied in early pregnant gilts. The injection of PGE2 under the perimetrium caused an increase (P<0.001) in PGE2 concentration in both uterine venous effluent and ovarian and uterine arterial blood. The infusion of PGE2 into the ovarian artery increased the concentration of progesterone in ovarian venous blood on day 13 of pregnancy during (P<0.05) and after (P<0.001) infusion, and on day 14 of pregnancy after infusion (P<0.01). In conclusion, local destination transfer of PGE2 from uterine lymph and venous blood to the ovary may affect luteal function, and retrograde transfer of PGE2 to the arterial blood supplying the uterus may contribute to the prevention of regressive changes of the endometrium in early pregnant gilts.

Male-induced short oestrous and ovarian cycles in sheep and goats: a working hypothesis

The existence of short ovulatory cycles (5-day duration) after the first male-induced ovulations in anovulatory ewes and goats, associated or not with the appearance of oestrous behaviour, is the origin of the two-peak abnormal distribution of parturitions after the "male effect". We propose here a working hypothesis to explain the presence of these short cycles. The male-effect is efficient during anoestrus, when follicles contain granulosa cells of lower quality than during the breeding season. They generate corpora lutea (CL) with a lower proportion of large luteal cells compared to small cells, which secrete less progesterone, compared to what is observed in the breeding season cycle. This is probably not sufficient to block prostaglandin synthesis in the endometrial cells of the uterus at the time when the responsiveness to prostaglandins of the new-formed CL is initiated and, in parallel, to centrally reduce LH pulsatility. This LH pulsatility stimulates a new wave of follicles secreting oestradiol which, in turn, stimulates prostaglandin synthesis and provokes luteolysis and new ovulation(s). The occurrence of a new follicular wave on days 3-4 of the first male-induced cycle and the initiation of the responsiveness to prostaglandins of the CL from day 3 of the oestrous cycle are probably the key elements which ensure such regularity in the duration of the short cycles. Exogenous progesterone injection suppresses short cycles, probably not by delaying ovulation time, but rather by blocking prostaglandin synthesis, thus impairing luteolysis. The existence, or not, of oestrous behaviour associated to these ovulatory events mainly varies with species: ewes, compared to does, require a more intense endogenous progesterone priming; only ovulations preceded by normal cycles are associated with oestrous behaviour. Thus, the precise and delicate mechanism underlying the existence of short ovulatory and oestrous cycles induced by the male effect appears to be dependent on the various levels of the hypothalamo-pituitary-ovario-uterine axis.

A dominant ovarian follicle induces unilateral changes in the origin of the blood supply to the tubal corner of the uterus

BACKGROUND

The blood supply to the tubal corner of the uterus may originate from the uterine and ovarian arteries. The border of supply from the arteries has been found to move in young women; the change seemed dependent on ovarian steroid production. The present work investigated whether the border of supply could differ between the two sides of the uterus in the same woman having one dominant follicle (>10 mm).

METHODS

Vagina was flushed with saline of room temperature in 15 women with a dominant follicle >10 mm. The temperature was measured in the mid-uterine lumen and in the tubal corner of the uterus at 2, 5 and 7 min after starting cooling. The investigation was repeated 30 min later measuring the temperature in the other tubal corner.

RESULTS

The temperature decrease was, as found in previous investigations, more pronounced in the uterine cavity than in the tubal corners. However, a difference was found between the two tubal corners. At all measurement times the decrease was significantly smaller in the tubal corner corresponding to the dominant follicle than in the contralateral side.

CONCLUSIONS

In our model, 'cold' is transferred from the vaginal venous blood to the uterine artery and the cooling defines the supply area of the uterine artery. Therefore, the results indicate that the area of supply from the ovarian artery in the tubal corner ipsilateral to the dominant follicle is greater than that in the contralateral side. It is possible to speculate that this difference is related to the hormonal production of the dominant follicle.

Morphological analysis of transportation pathways of microspheres after their introduction into the uterine horn cavity in cyclic pigs

Countercurrent transfer is thought to be one of the most important mechanisms involved in the transfer of substances between the uterus and oviduct. The present study was aimed at recognizing other putative transportation pathways from the uterine cavity through the oviduct onto the surface of and into internal ovarian structures. Microspheres (latex beads, 0.8 microm in diameter) were introduced into the uterine horn cavity of pigs, for 30 min, at various days of the estrous cycle. The transportation pathways of the beads were then analyzed by light and electron microscopy. The transport of microspheres through the oviduct canal into ovarian tissues took place on each day of the estrous cycle. The largest numbers of microspheres passed through the tunica albuginea to the corpora lutea. Some of microspheres also reached the surface of the uterine ligament through the oviduct canal, where they attained the lumen of blood and lymphatic vessels, mainly of the vascular subovarian (VSP) and paraovarian lymphatic plexus (PLP), via the lymphatic stomata pathway. Transport of microspheres also took place simultaneously through the uterine and oviduct walls and from particular organs through blood and lymphatic vessels. Although the present results do not exclude the participation of countercurrent transfer between venous, lymphatic, and arterial vessels, they provide morphological evidence for the presence of direct transportation pathways of substances, released into the uterine lumen, into ovarian tissues through the oviduct canal.

Retrograde transfer of steroid hormones to the ovary in luteal and follicular phases of porcine oestrous cyclein vivo

The efficiency of the retrograde transfer of steroid ovarian hormones from the ovarian effluent into blood supplying the ovary and the rate of its back transport to the ovary were determined for the first time in in vivo conditions. Sexually mature gilts (n = 25) were used in the physiological study. The concentration of oestradiol and progesterone in blood collected from the ovarian artery was higher in both the follicular phase (by 87.9 +/- 2.9% and 150.0 +/- 4.8%, respectively, P < 0.001) and the luteal phase (by 82.1 +/- 3.9% and 77.7 +/- 2.7%, respectively, P < 0.001) than in systemic blood reaching the initial part of the ovarian artery. The high efficiency of the retrograde transfer was not dependent on the concentration of hormones in the ovarian venous blood. However, the efficiency and rate of the retrograde transfer differed between phases of the oestrous cycle. We suggest that such effective retrograde transfer of ovarian hormones must affect the secretory function of the ovary.

Ovarian follicular fluid, progesterone and Ca2+ ion influences on sperm release from the fallopian tube reservoir

As a means of determining whether ovarian follicular fluid reaches the functional sperm reservoir in the caudal isthmus of the Fallopian tube shortly after ovulation, 0.01-0.02 ml aliquots of whole or steroid-free follicular fluid were introduced into the distal extremity of the isthmus within 1 hr before ovulation. Eggs were recovered during a second intervention 4 hr 45 min-6 hr 10 min after treatment and examined by phase-contrast microscopy for the normality of fertilisation. In a separate experiment, 0.01-0.02 ml aliquots of 10 microM calcium ionophore solution were introduced into the same site in comparable animals. Sixty-nine fertilised eggs were recovered from 12 fallopian tubes treated with whole follicular fluid, of which 24 (34.8%) were polyspermic. The 12 contralateral control tubes (PBS-treated) yielded 47 fertilised eggs, of which only one (2.1%) was polyspermic (P < 0.001). Steroid-free aliquots of the same follicular fluid introduced bilaterally into eight fallopian tubes (4 animals) resulted in recovery of 59 fertilised eggs, of which only one (1.7%) was polyspermic. Treatment with ionophore solution yielded a 41.6% incidence of polyspermy (10 of 24 eggs from four tubes) compared with 3.8% polyspermy (1 egg) from the control tubes (P < 0.01). Dispermy was the principal form of polyspermy. The numbers of accessory spermatozoa on/in the zona pellucida were increased by the experimental treatment. Follicular fluid passing down the fallopian tube ampulla at ovulation was therefore considered not to be the physiological stimulus for an initial, tightly-controlled release of spermatozoa from epithelial binding in the caudal isthmus. Indeed, because such sperm activation commences shortly before ovulation, a locally transmitted ovarian programming with relatively high concentrations of follicular hormones remains the favoured model. Although pre-ovulatory progesterone is considered to be the coordinating steroid of increasing influence in these pre-fertilisation events, its effects are proposed to be modulated in the endosalpinx by mobilisation of Ca2+ ions into a discrete population of bound spermatozoa. Results of the steroid-free follicular fluid and calcium ionophore treatments stand in support.

Local increase of ovarian steroid hormone concentration in blood supplying the oviduct and uterus during early pregnancy of sows

Countercurrent transfer in the ovarian vascular pedicle elevates the concentration of steroid hormones in blood supplying the oviduct and periovarian part of the uterus during the estrous cycle in the pig. This study was conducted to determine whether during early pregnancy the arterial blood supply to the oviduct and uterus carries greater concentration of steroid hormone than systemic blood. The concentration of ovarian steroid hormones (progesterone, estradiol-17 beta, estrone, androstenedione and testosterone) was measured in 40 gilts on Days 12, 18, 25 or 35 of pregnancy. Silastic catheters were inserted: a) into the jugular vein, b) into the branch of uterine artery close to the ovary (proximal to the ovary) and c) into the branch of the uterine artery close to the cervix (distal to the ovary). On the day following surgery simultaneous blood samples from cannulated vessels were collected every 20 min for 3 hours. The concentration of steroid hormones was determined by radioimmunoassay. The mean concentrations of studied hormones in branches of the uterine artery proximal and distal to the ovary were significantly greater than in the jugular vein (P < 0.001) by 18 to 69% and 7 to 31%, respectively. The concentrations of hormones in proximal and distal to the ovary branch of the uterine artery were also significantly different (P < 0.001). The increase in concentrations of the measured hormones did not differ considerably between investigated days of pregnancy. It is concluded that during maternal recognition of pregnancy, formation of the corpus luteum of pregnancy, implantation of the embryo and the placenta elongation the oviduct and uterus are supplied with locally elevated concentration of steroid hormones compared to systemic blood.

Involvement of adrenoceptors in the ovarian vascular pedicle in the regulation of counter current transfer of steroid hormones to the arterial blood supplying the oviduct and uterus of pigs

1. On Day 10 of the oestrous cycle in pigs, after laparotomy noradrenaline (NA), methoxamine (alpha 1-adrenomimetic, M), Prazosin (alpha 1-adrenolytic, Pr) in total doses of 4 mumol, and saline were infused (10 min) into the superficial layer of mesovarium on both sides of the ovarian pedicle vasculature, close to the ovary. 2. Blood flow in the ovarian artery, heart rate and progesterone (P4) and androstenedione (A4) secretion from the ovary and their concentrations in the ovarian venous effluent, as well as the concentrations of P4 and A4 in the blood supplying the oviduct and the uterus, were determined. 3. A significant increase of P4 and A4 secretion after NA and M infusion and increased concentrations of P4 and A4 in the ovarian venous effluent were found, but these changes did not influence the counter current transfer of hormones from the venous effluent into arterial blood supplying the oviduct and the uterus. 4. Infusion of Pr caused a significant decrease of P4 and A4 secretion and their concentrations in the ovarian venous effluent and significantly increased A4 concentration in the blood supplying the oviduct and uterus. 5. The results indicate that stimulation of alpha 1-adrenoceptors in the area of ovarian vasculature did not influence, whereas block of alpha 1-adrenoceptors affected, the local concentration of steroid hormones in the blood supplying the oviduct and the part of the uterus proximal to the ovary, despite the changes in the concentrations of steroid hormones in the ovarian effluent.

Local regulation of oviductal blood flow

1. Blood flow to the oviduct is implicated in the genesis and maintenance of oviductal fluid, in this way contributing to the creation of an adequate medium for ovum/embryo physiology. Therefore, factors controlling the tone of the vessels supplying the oviduct would be expected to affect its luminal environment. In addition, cyclic changes in oviductal blood flow have been suggested to have mechanical functions in the transport of the ovum/embryo. 2. The vascular supply to the oviduct has a prominent adrenergic vasomotor control. A dense adrenergic innervation, together with the presence of a predominant population of alpha(1)-adrenoceptors, provides a contractile regulatory mechanism of oviductal blood flow. No evidence is available on the presence of beta-adrenoceptors. The scanty cholinergic innervation of mammalian oviduct is mainly confined to the vessels, where acetylcholine (ACh) has a vasodilatory effect by releasing endothelium-derived relaxing factors. 3. The presence of nerves containing neuropeptides has been shown in the oviduct. Specifically, a high density of neuropeptide Y- and vasointestinal peptide-containing nerve fibers has been found in relation to blood vessels, but their role in the neutral control of the oviduct blood flow remains to be established. To date, it is not known whether or not oviductal blood vessels receive perivascular nitrergic nerves. 4. Relaxing and contracting factors derived from endothelium also seem to have a modulatory role on oviductal vascular tone. Neurotransmitters or autacoids, such as ACh and histamine, acting on endothelial receptors, release nitric oxide (NO), which relaxes oviductal arteries through guanylyl cyclase activation and accumulation of cyclic GMP. In addition, the release of an endothelium-derived hyperpolarizing factor (EDHF), distinct from NO, by ACh has been shown in oviductal arteries. It acts through the opening of low-conductance Ca(2+)-activated K+ channels leading to hyperpolarization and relaxation. Furthermore, potent and long-lasting contractions induced by the endothelium-derived contractile factor, endothelin (ET), points to its role in the long-term regulation of oviductal vascular tone. 5. A particularly high density of 5-hydroxytryptamine (5-HT) and histamine, present in mast cells clustered in the vicinity of blood vessels, has been described in the oviduct. It is known that histamine elicits a relaxation of oviductal arteries that is partially endothelium-dependent and mediated by the activation of H1-receptors. The implication of histamine in both the increase in blood flow and edema around ovulation, as well as the existence of a functional antagonism between histamine and 5-HT in the regulation of oviductal blood flow, await further investigation. 6. Other factors, such as relaxing and contracting cyclooxygenase-derived products, may also participate in the modulation of blood flow to the oviduct. 7. An overall endocrine regulation of the oviductal vascular supply exists, acting by both direct effects on smooth muscle and modulation of neural and autocrine factors. This control enables cyclic changes in blood flow to the oviduct that are tightly coupled to the reproductive functions of the tube.

Total content of prostaglandin F2 alpha in the endometrium and myometrium from various sections of the porcine uterine horn during the estrous cycle

The purpose of this study was to determine effects of various stages of the estrous cycle on the content and concentration of PGF2 alpha in endometrium and myometrium in different segment of the uterine horn and whether different methods of expressing PGF2 alpha data would affect interpretation of results. Total content of PGF2 alpha in the endometrium and myometrium of the entire uterine horn, and PGF2 alpha concentrations in five sections of uterine horn each of equal length (1 to 5 beginning from the ovarian end) were measured in gilts during three different phases of the estrous cycle: the early luteal phase (Days 3 to 6 of the estrous cycle), mid-luteal phase (Days 9 to 12), and during luteolysis (Days 15 to 18). The total content of PGF2 alpha in the early and mid-luteal phases was similar (P > or = 0.05) in both the endometrium and myometrium. During luteolysis the content of PGF2 alpha in the endometrium and myometrium increased 7-fold and 4-fold, respectively, when compared to the early luteal phase. The distribution of PGF2 alpha was similar throughout the length of the uterine horn and this did not change during the phases of the cycle studied. The PGF2 alpha concentrations during different phases of the estrous cycle differed with methods of expressing the data i.e. ng g-1 tissue, ng mg-1 DNA, ng mg-1 protein, but the relative differences were not appreciably altered.