Local effect of progesterone infusion into ovarian artery on activin A and inhibin alpha-subunit secretion during the middle luteal phase in gilts

The present study was undertaken to elucidate whether an increased, but physiological, amount of progesterone (P4) supplied to the porcine corpus luteum affects luteal secretion of activin A and inhibin alpha-subunit (Inhalpha) in freely moving gilts. On day 9 of the estrous cycle (EC), both ovarian arteries and both ovarian veins of gilts (n = 5) were cannulated. Progesterone was infused into the right ovarian arteries in gilts on days 10, 11 and 12 of the EC at a rate adequate to its physiological retrograde transfer found during the middle luteal phase of the EC. The P4 infusion rate was 0.62 microg/min (day 10), 2 x 0.62 microg/min (day 11) and 3 x 0.62 microg/min (day 12). The left ovarian arteries were infused with saline (control). Blood samples were collected from both ovarian veins on days 10-12 of the EC before and after P4 or saline infusion. The mean plasma activin A level in the ovarian vein ipsilateral to the P4-infused ovary was higher (P < 0.0001) on days 10-12 of the EC than this found in the contralateral ovarian vein. The level of activin A in the ovarian vein ipsilataral to the infusion of P4 was higher on days 11 (P < 0.01) and 12 (P < 0.0001) and tended to be higher (P < 0.07) on day 10 of the EC than this in contralateral ovarian vein. The level of Inhalpha in the ovarian vein ipsilateral to the P4-infused ovary on days 10-12 of the EC was not significantly different (P > 0.05) than this found in the contralateral ovarian vein. The results of the present study indicate that a local elevation of P4 concentration in blood supplying the ovary during the middle luteal phase of the porcine EC affects ovarian secretion of activin A. The effect of P4 on the secretion of activin A suggested the existence of a short regulatory loop of a positive feedback between P4 being retrogradely transferred into the ovary and the secretion of this peptide.

Retrograde transfer of 125I-radiolabelled activin and inhibin in the periovarian vascular complex in the sow

This study investigated whether activin A and an inhibin-alpha subunit fragment (INHalpha) could permeate in a periovarian vascular complex from ovarian effluent into the ovarian artery and be retrograde transferred into the ovary. Radiolabelled activin A (125I-activin A) and INHalpha (125I-INHalpha) were injected (2.7 x 10(7) dpm) into follicles or corpora lutea (CL). It was demonstrated that 125I-activin A and 125I-INHalpha were released into the ovarian effluent and permeated into the arterial blood supplying the ovary in both phases of the cycle. The concentration of 125I-activin A in ovarian arterial blood was higher in the luteal phase (LP) than in the follicular phase (FP) (P<0.0001) in contrast to 125I-INHalpha which was higher in the FP (P<0.0001). The concentration of 125I-activin A in uterine tissues generally did not differ between the phases of the estrous cycle, but the concentration of 125I-INHalpha was higher (P<0.05) in the FP than in the LP. The concentration of 125I-activin A was higher in the LP in samples of endometrium and myometrium (P<0.05), as well as mesometrium (P<0.01), and higher in the FP in samples of mesometrium (P<0.05) close to the ovary than in the samples adjoining the uterine body. In the FP, the concentration of 125I-INHalpha was higher in endometrium and mesometrium close to the ovary than in samples adjoining the uterine body (P<0.05). In conclusion, the study demonstrated that it was possible for INHalpha and activin A to be retrograde transferred to the ovary. Thus this transfer could elevate their concentration in arterial blood supplied to the ovarian follicles or CL and may influence production of these peptides in the ovary, modulating ovarian function.

The effect of intramuscular injections of boar pheromone 5alpha-androstenol on the hormonal regulation of the estrous cycle in hypoosmatic gilts

Until 1999 it was accepted that pheromones act exclusively by stimulating the dendritic receptors present in olfactory epithelium. Cycling gilts with an experimentally-disrupted neural olfactory pathway were used to test the hypothesis that boar pheromone 5alpha-androstenol may affect the secretion of hormones involved in the regulation of the estrous cycle by the humoral pathway. On day 12 of the estrous cycle the nasal cavity of gilts (n=15) was irrigated with zink sulfate solution. From day 16 to 20, the experimental group (n=10) was injected intramuscularly with 5alpha-androstenol (20 microg) twice a day. Blood samples were collected from the jugular vein at 4 h intervals on days 17-21 to estimate plasma concentration of LH, oxytocin, estradiol-17beta, testosterone and progesterone. The experimental group displayed a significantly lower mean concentration of LH than the control animals (P<0.0001). The decrease in concentration of LH was accompanied by the reduction of oxytocin (P<0.001), estradiol-17beta (P<0.001) and testosterone (P<0.01) secretion. These results demonstrated that 5alpha-androstenol influenced hormonal regulation by humoral pathway and might be considered to be the priming pheromone in gilts.

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.

Boar pheromone androstenol may affect the ovarian morphology in cycling gilts by humoral pathway

Up to 1999 it was accepted that pheromones act exclusively by stimulation of dendritic receptors of olfactory neurons massed in the olfactory epithelium, but in 1999-2000, the presence of local humoral pathway for transfer of boar pheromone androstenol from the nasal cavity to the hypophysis and brain was demonstrated in gilts. The aim of the present study was to ascertain whether boar pheromone androstenol may affect by humoral pathway the ovarian morphology in gilts. This study demonstrated that intramuscular injections of androstenol in the follicular phase (17-20 day) of the estrous cycle in anosmatic gilts, in which the neural pathway for olfactory function was experimentally blocked, produced lack of the ovulation and changes in the morphology of ovaries. Histological analysis of the ovaries, collected seven days after androstenol injections, revealed the absence of corpora lutea and healthy follicles of a diameter over 6 mm as well as a significant decrease in the number of the follicles up to I mm in diameter (P<0.01). In androstenol-treated gilts, the number of atretic follicles from 1 mm to 6 mm in size was increased (P<0.01-P<0.001) and in one gilt cysts were found. The obtained results provided some evidence that in gilts in addition to acting by standard neural pathway, androstenol as a priming pheromone may affect the ovarian morphology by a humoral pathway.

Retrograde transfer of ovarian steroid hormones to the ovary in the porcine periovarian vascular complex

The aim of the present study was to investigate the mechanism of the retrograde transfer of ovarian steroid hormones from the ovarian lymphatic and venous effluent to the arterial blood supplying the ovary. In the first experiment, reproductive organs were collected from gilts in the luteal (n = 10) and follicular (n = 10) phase of the oestrous cycle. The ovary with the mesovarium was isolated and perfused through the ovarian artery with warmed, oxygenated autologous blood. The concentrations of progesterone and oestradiol in ovarian arterial blood increased on passing through the ovarian artery to the ovary, in the luteal phase, from 20.3 +/- 2.1 to 31.4 +/- 3.9 ng ml(-1) (P < 0.001) and from 6.2 +/- 0.8 to 11.4 +/- 1.4 pg ml(-1) (P < 0.001), respectively, and in the follicular phase, from 1.2 +/- 0.2 to 2.2 +/- 0.4 ng ml(-1) (P < 0.001) and from 8.2 +/- 1.8 to 13.2 +/- 2.3 pg ml(-1) (P < 0.001), respectively. Approximately 17.5 +/- 3.9 % of the progesterone and 12.6 +/- 1.7 % of the oestradiol found in the ovarian venous effluent was retrogradely transferred from the ovarian venous blood to the ovary in the luteal phase. In the follicular phase, these values were 10.1 +/- 2.0 % and 8.6 +/- 1.4 %, respectively. The efficiency of retrograde transfer of oestradiol and the rate of retrograde transfer of progesterone differed between phases of the oestrous cycle (P < 0.05 and P < 0.0001, respectively). A direct relationship between the concentration of the steroids in the venous effluent and the efficiency and rate of the retrograde transfer to the ovary was not found. In the second experiment (luteal phase, n = 10; follicular phase, n = 5), the concentration of progesterone and oestradiol increased in both ovarian arterial blood (P < 0.0001) and in the venous effluent (P < 0.0001) after administration of the steroids into the lymphatic vessels of the isolated mesovarium with separated ovary. In the third experiment (follicular phase, n = 5), with the mesovarium isolated after the ovary was removed and ovarian venous blood flowing out under the force of gravity (without the blood pressure in the ovarian vein), it was demonstrated that the veno-venous network covering the branches of the ovarian artery was supplied with the blood flowing out from the mesovarian tissue and that the filling of the veno-venous network was dependent on the blood pressure in the ovarian artery. We conclude that the effective retrograde transfer of steroid hormones from ovarian venous and lymphatic effluent to the ovary is accomplished not only by the classical counter-current exchange mechanism, but also as a result of complex processes that may be dependent on a specific part of the circulation of the blood and lymph in the periovarian vascular complex of the mesovarium.

Apoptotic cell death in the porcine endometrium during the oestrous cycle

It has been reported that apoptosis plays an essential role in controlling the physiological cell kinetics in the human and rodent endometrium but this type of death has never been studied in the porcine endometrium. The aim of this study was to investigate the apoptotic cell death in the porcine endometrium during the middle (Days 9-11) and late (Day 13) luteal phase, during the luteolysis (Day 15) and early follicular phase (Days 17-19) of the oestrous cycle. Apoptotic cells were identified by in situ DNA 3'-end labelling method. It was revealed that the greatest number of apoptotic cells in the luminal and glandular epithelium was found on Days 17-19 and on Day 15 of the oestrous cycle, respectively. In the stroma, the greatest number of these cells was found on Days 9-11. Our data have shown that in the porcine endometrium, both epithelial and stromal cells undergo apoptosis and that the number of apoptotic cells varies depending on the phase of the oestrous cycle.

Humoral pathway for transfer of the boar pheromone, androstenol, from the nasal mucosa to the brain and hypophysis of gilts

Signaling and priming pheromones play an important role in intraspecies behavioral and sexual interactions and in the control of reproduction. It is generally accepted that pheromones act by stimulating the dendritic receptors in the mucus-imbedded cilia of olfactory neurons massed in the olfactory epithelium. The boar pheromone androstenol, known to induce sexual behavior in pigs, is 1 of 2 pheromones that have been chemically defined, tritiated and thus made available for use in studies. In Experiment 1, sexually mature cyclic gilts at Days 16 to 21 of the estrous cycle were humanely killed and the heads separated from the bodies. The heads were attached to a perfusion system using heated, oxygenated, heparinized, autologous blood. A total amount of 10(8) dpm (758 ng) of 3H-5 alpha-androstenol (3HA) was either infused into the angularis oculi veins that drain the nasal cavities (n = 7) over a 5-min period or applied through intranasal catheters onto the mucose surface (n = 16) for 2 min. In both groups frequent blood samples were collected from the carotid rete and from venous effluent. Concentration of 3HA in the arterial blood of the carotid rete after direct (into angularis oculi veins) or indirect (onto the nasal mucosa) administration of 3HA into veins draining the nasal cavities was significantly higher than background radioactivity before 3HA administration (P < 0.0001 and P < 0.05, respectively). The 3HA was selectively accumulated (compared with the respective control tissue) in the neurohypophysis (P < 0.001), adenohypophysis (P < 0.01), ventromedial hypothalamus (P < 0.05), corpus mammillare (P < 0.01), and perihypophyseal vascular complex (P < 0.001). In a second in vitro experiment, active uptake of 3HA into the nasal mucosa of the proximal, respiratory segment of the nasal cavity was observed. These results demonstrate a humoral pathway for the transfer of pheromones from the nasal cavity to the hypophysis and brain. Androstenol was taken up by the respiratory part of the nasal mucosa, resorbed into blood, transported to the cavernous sinus and transferred into the arterial blood of the carotid rete (supplying the hypophysis and brain), and then selectively accumulated in the hypophysis and certain brain structures.

The inhibitory effect of hCG on counter current transfer of GnRH and the presence of LH/hCG receptors in the perihypophyseal cavernous sinus--carotid rete vascular complex of ewes

The existence of the hormone passage from venous blood into arterial blood in the area of the perihypophyseal vascular complex has been demonstrated in some mammals, but its mechanism has not been defined. To study the regulatory mechanism we infused hCG into perihypophyseal cavernous sinus of ovariectomized, conscious ewes to test if the hCG would affect putative LH/hCG receptors and inhibit counter-current transfer of GnRH from the venous cavernous sinus to the arterial carotid rete. The latter study was done on an isolated head model. Ewes were ovariectomized in mid-anestrus and, after 4 to 5 wk were used in the experiments. On the day of experiment ewes were treated intramuscularly with estradiol benzoate or oil vehicle, and 18 to 20 h later were infused either with a multielectrolyte solution or hCG for 2 h via the venae angularis oculi. Immediately thereafter the ewes were anesthetized and exanguinated, and subsequently decapitated. The isolated head was perfused with Dextran in multielectrolyte. The 125I-GnRH was infused into the cavernous sinus via the venae angularis oculi for 5 min; contemporaneous samples were taken from the carotid rete and both jugular veins at 1-min intervals. Transfer of 125I-GnRH from the cavernous sinus to the carotid rete was inhibited by hCG in ewes pretreated with estradiol benzoate but not with oil (P<0.005). We collected tissue samples from the vascular complex of the cavernous sinus and carotid rete of cyclic ewes to determine the presence of LH/hCG receptors. In situ hybridization showed the presence of LH/hCG receptor mRNA transcripts in the walls of both arterial and venous compartments of the cavernous sinus-carotid rete complex, and immunohistochemistry revealed the presence of receptor proteins. These novel findings confirm previously obtained data suggesting that LH is a modulatory factor for the counter-current transfer of neuropeptides from the venous blood of the cavernous sinus to the arterial blood supplying the brain and hypophysis. The LH could modulate 125I-GnRH transfer acting directly on the vascular smooth muscle.

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.

Counter current transfer of beta-endorphin in the perihypophyseal cavernous sinus--carotid rete vascular complex of sheep

This study was performed to answer the question of whether counter current retrograde transfer of beta-endorphin in the perihypophyseal cavernous sinus-carotid rete vascular complex depends on the reproductive activity of sheep and if this transfer depends on membrane Na+ K+ ATP-ase blocking by ouabain. Sheep were anaesthetised and the jugular vein and the carotid artery were cannulated on both sides. Multielectrolitical liquids (Solfin, Polfa "Kutno", Poland): 500 ml of Solfin with heparin (25,000 IU), or Solfin with heparin and ouabain (Sigma, St. Louis, USA) in concentrations of 10(-5) or 10(-4) mol 1(-1) were infused into the brain through the carotid artery. Heparinized blood was collected through the carotid artery. After exsanguination, the head with the neck was removed. The isolated head was supplied with oxygenated, heated, autologous blood diluted with Solfin (4:1) without or with ouabain in concentration of 10(-5) or 10(-4) mol 1(-1). Blood pressure and temperature were measured throughout the duration of the experiment. During the experiment 125I-beta-endorphin (7.9 x 107 dpm) dissolved in 10 ml of Solfin was infused for 5 min (5 ml) into each cavernous sinus through the angularis oculi veins. Blood samples for radioactivity measurements were collected each min from the carotid rete (through the opposite carotid artery to the artery supplying the brain with arterial blood) and from both jugular veins. In all the experiments significant 125I-beta-endorphin radioactivity was found in arterial blood supplying the brain and hypophysis in the early luteal phase in sheep. No radioactivity was found (with the exception of one animal) in sheep during seasonal anoestrus. A blockage of Na+ K+ ATP-ase by ouabain administered during exsanguination and during head perfusion with dose of 10(-4) mol 1(-1) reduced beta-endorphin counter current transfer to arterial blood, but this effect was not evident with the dose of 10(-5) mol 1(-1). Increased blood pressure was observed in all the experiments with either dose of ouabain.

Countercurrent transfer of 125I-LHRH in the perihypophyseal cavernous sinus-carotid rete vascular complex, demonstrated on isolated pig heads perfused with autologous blood

The objective of the study was to determine whether the local permeability of luteinizing hormone-releasing hormone (LHRH) from the venous blood of the perihypophyseal cavernous sinus into the arterial blood of the carotid rete, supplying the brain and hypophysis in gilts, depends on the day of the estrous cycle, as well as to determine whether this transfer exists when LH concentration in the blood is reduced (the experimental short-loop negative feedback for LH secretion after estradiol injection in ovariectomized gilts). Experiments were conducted on isolated gilt heads with necks, on chosen days of the estrous cycle (n = 40), and on previously ovariectomized gilts treated with estradiol benzoate (EB) (n = 5) or corn oil (n = 3). After exsanguination, the gilt heads with necks were disarticulated and about 30-45 min later were supplied with autologous, oxygenated, and heated blood at a stable blood flow and pressure through the left carotid artery for 30 min. 125I-LHRH was infused into both cavernous sinuses through the cannulated angularis oculi veins for 5 min. After 125I-LHRH infusion, radiolabeled LHRH was found (P < 0.001) in arterial blood taken from the carotid rete through the open right carotid artery in all animals used in the experiment: on Days 1-2 (six gilts), on Days 12-14 (seven gilts) of the estrous cycle, and in five ovariectomized gilts during negative feedback for LH surge (40 hr after EB). No significant radioactivity of 125I-LHRH was found in the arterial blood on Days 3-5 (n = 6), 9-11 (n = 4), and 15-21 (n = 17) of the estrous cycle. A very low level of radioactivity was found in the ovariectomized control group after the injection of corn oil (n = 3). These results provide evidence for the permeability of LHRH from the venous to the arterial blood and its retrograde transport with the arterial blood to the hypophysis and brain, after the ovulation period (Days 1-2) and on Days 12-14 of the estrous cycle. This suggests that a close relationship exists between the day of the estrous cycle and LHRH permeability from the venous to the arterial blood in the perihypophyseal cavernous sinus-the carotid rete complex in gilts-and that this mechanism may be included in a short-loop feedback for LHRH secretion.

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.

Cytokine and alloantibody networks in long term cardiac allografts in rat recipients treated with rapamycin

Treatment with rapamycin (RPM) prevents accelerated rejection of (LEW x BN)F1 cardiac allografts in LEW rats presensitized with BN skin grafts. This study analyzed the influence of RPM on cytokine (IL-2, IL-4, IL-10, and IL-12) and alloantibody networks in this model. Accelerated (24-h) rejection was associated with strong expression of intragraft IL-2 and IL-12 (p40) mRNAs, which reached maximal levels 3 to 6 h post-transplantation. IL-4 and IL-10 mRNAs were readily detectable throughout the observation period. RPM therapy abrogated rejection at 24 h and prolonged cardiac allograft survival to about 50 days. This effect was correlated with a profound initial depression of IL-2 mRNA; delayed expression of IL-2 mRNA was detected in well functioning grafts at &gt; 20 days. In RPM-treated hosts, expression of IL-12 (p40) mRNA was low at the early time points (6-24 h), but prominent in long term grafts. The expression of both IL-4 and IL-10 mRNAs was preserved in RPM-conditioned hosts. Immunohistologic analysis of long term allografts revealed an interstitial cellular infiltrate and areas of intimal proliferation within small arteries indicative of early transplant arteriosclerosis. Analysis of cytokine proteins showed dense labeling of mononuclear and some endothelial cells for IL-4 and IL-12 (p70), but not for IL-2 or IFN-gamma alloantibody in the early post-transplant period. However, an increase in circulating and intragraft IgM and, to a lesser extent, IgG, primarily of the IgG2b subclass, was evident in long term recipients. Thus, RPM treatment reduces, but does not completely inhibit, the expression of Th1-type and preserves the expression of Th2-type cytokines. The demonstration of IL-12 in long term allografts after RPM therapy may reflect late activation of macrophages that, coupled with the appearance of IgG2b, may contribute to the chronic rejection of cardiac allografts.

Cytokine and alloantibody networks in long term cardiac allografts in rat recipients treated with rapamycin

Treatment with rapamycin (RPM) prevents accelerated rejection of (LEW x BN)F1 cardiac allografts in LEW rats presensitized with BN skin grafts. This study analyzed the influence of RPM on cytokine (IL-2, IL-4, IL-10, and IL-12) and alloantibody networks in this model. Accelerated (24-h) rejection was associated with strong expression of intragraft IL-2 and IL-12 (p40) mRNAs, which reached maximal levels 3 to 6 h post-transplantation. IL-4 and IL-10 mRNAs were readily detectable throughout the observation period. RPM therapy abrogated rejection at 24 h and prolonged cardiac allograft survival to about 50 days. This effect was correlated with a profound initial depression of IL-2 mRNA; delayed expression of IL-2 mRNA was detected in well functioning grafts at > 20 days. In RPM-treated hosts, expression of IL-12 (p40) mRNA was low at the early time points (6-24 h), but prominent in long term grafts. The expression of both IL-4 and IL-10 mRNAs was preserved in RPM-conditioned hosts. Immunohistologic analysis of long term allografts revealed an interstitial cellular infiltrate and areas of intimal proliferation within small arteries indicative of early transplant arteriosclerosis. Analysis of cytokine proteins showed dense labeling of mononuclear and some endothelial cells for IL-4 and IL-12 (p70), but not for IL-2 or IFN-gamma alloantibody in the early post-transplant period. However, an increase in circulating and intragraft IgM and, to a lesser extent, IgG, primarily of the IgG2b subclass, was evident in long term recipients. Thus, RPM treatment reduces, but does not completely inhibit, the expression of Th1-type and preserves the expression of Th2-type cytokines. The demonstration of IL-12 in long term allografts after RPM therapy may reflect late activation of macrophages that, coupled with the appearance of IgG2b, may contribute to the chronic rejection of cardiac allografts.

Downregulation of intragraft IFN-gamma expression correlates with increased IgG1 alloantibody response following intrathymic immunomodulation of sensitized rat recipients

A single intrathymic injection of donor-specific spleen cells (2 x 10(7)) abrogates accelerated (24 hr) rejection of LBNF1 cardiac allografts in presensitized LEW rats and prolongs graft survival to about 11 days. This effect is donor-specific, gamma-irradiation-sensitive, thymus-dependent, and requires no concomitant therapy. We have recently shown that following intrathymic alloantigen administration, there is an earlier and increased systemic production of alloreactive IgM, and subsequently a premature isotype switching to IgG with the predominant IgG1 and IgG2a alloantibody responses. There is also a preferential binding of these IgG subclasses to the endothelium of well-functioning allografts. In this work, we analyzed the early cell activation and related cytokine elaboration patterns at the mRNA and protein levels by competitive template RT-PCR and immunohistochemistry, respectively. We found that prolonged cardiac allograft survival following intrathymic administration of donor spleen cells in presensitized rats was associated with markedly depressed intragraft IFN gamma mRNA and protein expression. Moreover, intrathymic allostimulation has led to a defect in the IL-2 pathway as the expression of IL-2 and IL-2R protein at the graft site was inhibited despite stable IL-2 mRNA levels. The inhibition of cell activation was also demonstrated by reduced MHC class II and the lack of ICAM-1, and TNF-alpha expression by immunohistochemistry. The expression of biologically active IL-12 (p70) by mononuclear and endothelial cells was detected in rejecting grafts between 3 and 12 hr. The well-functioning grafts after intrathymic allostimulation were devoid of IL-12 (p70), which in turn may have contributed to the downregulation of IFN-gamma mRNA and protein. Treatment with r.IFN-gamma, but not with r.IL-2, recreated the rejection response, and the characteristic IgG subclass pattern associated with accelerated graft loss. Hence, intrathymic immunomodulation with alloantigen results in selective inhibition of IFN-gamma-producing cells and a preferential upregulation of IgG1 alloantibodies. These data support the notion of the interlocked immunoregulatory roles of cytokine and alloantibody networks in rat allograft recipients.

The alloantibody network following intrathymic immunomodulation of sensitized rat recipients of cardiac allografts

An intrathymic injection of allogeneic spleen cells (2 x 10(7)) prevents accelerated (< 36 hr) rejection in sensitized LEW rats, and prolongs the survival of LBNF1 cardiac allografts to about 11 days. This effect is donor-specific, x-irradiation-sensitive and thymus-dependent, and it does not require adjunctive immunosuppressive therapy. We have recently shown that following intrathymic allo-Ag injection, host cell proliferative responses in lymphoid organs are markedly depressed as compared with untreated sensitized recipients. Little is known about how intrathymic immunomodulation may affect host humoral alloreactivity. In this work, we studied the dynamic interplay between the humoral responses, both in the circulation and at the graft site of sensitized hosts. Intrathymic allo-Ag exposure triggered a profound change in the utilization pattern of alloreactive IgM, IgG, and IgG subclasses compared with recipients receiving syngeneic cells. Administration of allo-Ag into the thymus at the time of sensitization resulted in an earlier and significantly increased systemic production of IgM, as shown by flow cytometry. Subsequently, isotype switching to IgG occurred prematurely and resulted in elevated levels of IgG1 and IgG2a. Indeed, the addition of such allo-Ab enriched serum suppressed the MLR assay in a dose-dependent manner. The binding of Ig to cardiac allografts was analyzed in eluates by flow cytometry, and by immunohistochemical staining at day 1 after transplantation. Intragraft IgM and IgG levels were consistently higher in well-functioning grafts following administration of allo-Ag, as compared with controls. IgG deposits at the graft site consisted predominantly of IgG1 and IgG2a, while significant amounts of IgG2b could only be detected in control hosts undergoing accelerated graft rejection. These data document that intrathymic injection of donor-specific allo-Ag in sensitized recipients leads to profound alterations of the host humoral alloresponses, and that such elevated allo-Ab levels interfere with the Ag reactivity or alloresponsive effector cells in vitro. These results support the notion that the pattern of allo-Ab utilization is indicative of the functional status of the alloimmune response in the transplant recipient.

Counter current transfer of oxytocin from the venous blood of the perihypophyseal cavernous sinus to the arterial blood of carotid rete supplying the hypophysis and brain depends on the phase of the estrous cycle in pigs

The objective of the present study was to determine whether or not the neuropeptide, oxytocin, can move by counter current transfer from venous blood of the perihypophyseal cavernous sinus into arterial blood of the carotid rete supplying the brain and hypophysis, and also whether this exchange depends on the day of the estrous cycle. Isolated heads of gilts (n = 37), on different days of the estrous cycle, were supplied with autologous, oxygenated and heated blood at a stable blood flow and pressure through the right carotid artery for 30 min. 125I-Oxytocin (125I-OT) was infused into both cavernous sinuses through the angularis oculi veins for 5 min. After 125I-OT infusion, radiolabeled oxytocin was found in arterial blood taken from the carotid rete in all 7 gilts on Days 1-3, and in 7 of 9 gilts on Days 12-13 of the estrous cycle. In general, the level of radioactivity in arterial blood during Days 12-13 was significantly lower (p < 0.002) than during Days 1-3 of the estrous cycle. No 125I-OT was found in arterial blood from Days 4 through 11 (n = 10) or from Day 14 to the beginning of ovulation (n = 11). These results provide evidence for the counter current transfer of oxytocin from hypophyseal and brain venous effluent (cavernous sinus) to arterial blood supplying the hypophysis and brain, during the ovulation period and the late luteal phase of the estrous cycle. The meaning of this process is not as yet known and needs further study.

Abrogation by rapamycin of accelerated rejection in sensitized rats by inhibition of alloantibody responses and selective suppression of intragraft mononuclear and endothelial cell activation, cytokine production, and cell adhesion

This study evaluated the efficacy and mode of action of rapamycin (RPM) in a model of accelerated (24-hr) rejection of LBNF1 cardiac allografts in specifically sensitized LEW rats. RPM treatment (0.25 mg/kg/day i.p.) between the day of sensitizing skin grafts (day -7) and subsequent heart (day 0) transplantation (Tx), abrogated fulminant rejection and prolonged cardiac allograft survival to 46 +/- 22 days (mean +/- SD, P < 0.0001). The delayed introduction of RPM until day -2 or day -1 was equally effective, whereas treatment initiated after cardiac Tx was ineffectual. Untreated accelerated rejection was associated with strong production of circulating IgM, whereas an IgG alloantibody response was not detected until after rejection was complete. RPM therapy (day -7 to -1) diminished this systemic IgM response and prevented the switch from IgM to IgG alloantibody production. Immunohistologic evaluation at 24 hr after cardiac Tx showed that compared with untreated hosts RPM treatment largely abolished intragraft cellularity, and was associated with decreased mononuclear and endothelial cell activation. Specifically, Ia and ICAM-1 upregulation was abolished, and no cells elaborating IL-2 or IFN-gamma were detected. In addition, RPM treatment prevented intragraft production of the proinflammatory cytokines IL-1 beta, IL-6, and IL-8. The effects of RPM therapy on recipient cellular responses were evaluated in vitro by mixed lymphocyte reaction. Surprisingly, the donor-specific proliferative response of cells from RPM-treated hosts at 1 or 7 days after Tx was markedly increased, compared with cells from rejecting, untreated controls, and bioassay of IL-2 within supernatants of MLR cultures showed comparable levels of IL-2 in both groups. The effects of RPM upon adhesion properties of lymph node lymphocytes were also tested in an in vitro binding assay. The binding of naive cells to sections of cardiac allografts collected from RPM-treated hosts at 24 hr post-Tx was decreased compared with that in untreated recipients. Interestingly, the binding of mononuclear cells to high endothelial venules of peripheral lymph nodes in RPM-treated hosts remained relatively high. Thus, treatment with RPM prevents and/or erases the sensitization, which otherwise leads to accelerated allograft rejection. Abrogation of allograft injury by RPM was associated with profound and long-lasting depression of host IgM and IgG alloantibody responses in the circulation, and selective downregulation of host cellular immunity and endothelial activation at the graft site. In contrast, antigen alloreactivity and endothelial adhesivity in peripheral lymphoid tissues were spared, indicating novel and potent selective effects of RPM therapy in allograft recipients.

CD4 mAb therapy modulates alloantibody production and intracardiac graft deposition in association with selective inhibition of Th1 lymphokines

The accelerated (24 h) rejection of (LEWxBN)F1 cardiac allografts (Tx) in LEW rats sensitized with BN skin grafts, is abrogated with CD4 mAb (BWH-4) administration between skin (day -7) and heart (day 0) transplantation (Tx survival ca. 11 days, p < 0.0001). This study analyzed the effects of CD4-targeted therapy upon host IgG and IgM alloantibody (allo-Ab) within the serum by two-color flow cytometry, and within the Tx, by immunohistology. These data were correlated with mRNA and protein production profiles of Th1 (IL-2, IFN-gamma) vs Th2 (IL-4) specific cytokines (polymerase chain reaction and/or immunohistology). Skin grafts elicited a strong systemic IgM allo-Ab response, which peaked at the time of cardiac Tx rejection at 24 h. It was associated with extensive deposits of IgM on Tx endothelium. Treatment with BWH-4 mAb diminished circulating IgM allo-Ab levels, and only low levels of IgM could be detected at the Tx site. Conversely, the low circulating IgG allo-Ab levels during rejection at 24 h in untreated recipients were accompanied by a strong labeling for intra-Tx IgG. BWH-4 mAb therapy did not prevent totally the switch of the IgM to IgG, but the IgG allo-Ab response was earlier, less intense and more transient than in untreated recipients. Accelerated rejection triggered sequential lymphokine mRNA expression in cardiac Tx, with the peak of transcription for IL-2 (6-12 h) preceding that for IL-4 (24 h). Interestingly, although CD4 targeted therapy virtually ablated the induction of IL-2 mRNA, it preserved transcription of the IL-4 gene. BWH-4 mAb therapy decreased otherwise abundant intra-Tx IL-2 and IFN-gamma, but allowed a vigorous elaboration of IL-4, confirming the translation of mRNA to the protein in vivo. Thus, CD4 mAb-mediated abrogation of accelerated cardiac Tx injury correlates with suppression of Th1 responses (depressed IL-2 and IFN-gamma production), but sparing of the Th2 function (enhanced IL-4 elaboration). Indeed, CD4 mAb-induced allo-Ab depression and immunosuppressive effects may reflect selective targeting of proinflammatory Th1-like cells and the multifaceted effects of IL-4 produced by unopposed Th2-like cells.

CD4 mAb therapy modulates alloantibody production and intracardiac graft deposition in association with selective inhibition of Th1 lymphokines

The accelerated (24 h) rejection of (LEWxBN)F1 cardiac allografts (Tx) in LEW rats sensitized with BN skin grafts, is abrogated with CD4 mAb (BWH-4) administration between skin (day -7) and heart (day 0) transplantation (Tx survival ca. 11 days, p &lt; 0.0001). This study analyzed the effects of CD4-targeted therapy upon host IgG and IgM alloantibody (allo-Ab) within the serum by two-color flow cytometry, and within the Tx, by immunohistology. These data were correlated with mRNA and protein production profiles of Th1 (IL-2, IFN-gamma) vs Th2 (IL-4) specific cytokines (polymerase chain reaction and/or immunohistology). Skin grafts elicited a strong systemic IgM allo-Ab response, which peaked at the time of cardiac Tx rejection at 24 h. It was associated with extensive deposits of IgM on Tx endothelium. Treatment with BWH-4 mAb diminished circulating IgM allo-Ab levels, and only low levels of IgM could be detected at the Tx site. Conversely, the low circulating IgG allo-Ab levels during rejection at 24 h in untreated recipients were accompanied by a strong labeling for intra-Tx IgG. BWH-4 mAb therapy did not prevent totally the switch of the IgM to IgG, but the IgG allo-Ab response was earlier, less intense and more transient than in untreated recipients. Accelerated rejection triggered sequential lymphokine mRNA expression in cardiac Tx, with the peak of transcription for IL-2 (6-12 h) preceding that for IL-4 (24 h). Interestingly, although CD4 targeted therapy virtually ablated the induction of IL-2 mRNA, it preserved transcription of the IL-4 gene. BWH-4 mAb therapy decreased otherwise abundant intra-Tx IL-2 and IFN-gamma, but allowed a vigorous elaboration of IL-4, confirming the translation of mRNA to the protein in vivo. Thus, CD4 mAb-mediated abrogation of accelerated cardiac Tx injury correlates with suppression of Th1 responses (depressed IL-2 and IFN-gamma production), but sparing of the Th2 function (enhanced IL-4 elaboration). Indeed, CD4 mAb-induced allo-Ab depression and immunosuppressive effects may reflect selective targeting of proinflammatory Th1-like cells and the multifaceted effects of IL-4 produced by unopposed Th2-like cells.

Cytokines, adhesion molecules, and the pathogenesis of chronic rejection of rat renal allografts

Little is known of the host immune mechanisms responsible for initiation and progression of chronic rejection. We describe immunopathologic features associated with progressively deteriorating function of kidney allografts in the F344-to-Lewis rat strain combination, which differ at MHC and non-MHC loci. Initial rejection in untreated recipients was controlled by a brief course of CsA (5 mg/kg/day, for 10 days), resulting in > 80% of recipients surviving up to a year despite declining renal function. In contrast to controls (isografts placed in untreated or CsA-treated Lewis rats), allografts from 12-16 weeks post-Tx showed segmental or global glomerulosclerosis, increasing tubular atrophy, interstitial fibrosis, and intimal proliferation leading ultimately to vascular occlusion. By flow cytometry, IgM and IgG alloantibodies peaked at 2-4 weeks, with a gradual decline to baseline thereafter. Immunohistology showed early and progressive deposition of IgM, IgG, C3, and fibrin in vessel walls and glomeruli. In addition, by 12 weeks, extensive infiltration by activated (IL-2R+) macrophages and CD4+ T cells were noted in glomeruli and blood vessels, in conjunction with staining for the cytokines TNF-alpha, IL-1, and IL-6. The persistent and dense intraglomerular expression of IL-6 was of particular interest, given its potent mitogenic effects for mesangial cells in vitro, and suggests a role for this cytokine as a mediator of mesangial expansion, advanced glomerular injury, and glomerulosclerosis in chronic rejection. Parallel timing of IL-6 and TNF-alpha expression was shown in serum samples by ELISA and bioassays. In vitro binding studies showed increased binding of naive host lymphocytes to allograft versus isografts, correlating with upregulation (peaking at week 16) of intercellular adhesion molecule-1 expression by graft endothelium. We conclude that cytokine production and upregulation of adhesion molecules occurring as part of a cellular immune response may be as important to the etiology of chronic rejection as the hitherto widely emphasized antibody-mediated host responses.

The association of enhancement of renal allograft survival by donor-specific blood transfusion with host MHC-linked inhibition of IgG anti-donor class I alloantibody responses

Donor-specific blood transfusion (DSBT) in animals and humans can either promote subsequent renal graft survival or lead to sensitization and graft rejection. Using a rat renal allograft model, we have examined whether the effects of DSBT on renal allograft outcome and IgG alloantibody responses are linked to the host MHC. In F1 rats produced by mating PVG (RT1c), a low IgG alloantibody responder to transfused ACI (RT1a) blood, with 3 different high-IgG responders [W/F (RT1u), LOU (RT1u), and LEW (RT1l)], high IgG alloantibody production was found to be inherited as a dominant trait and associated with acute rejection of ACI renal allografts. DSBT given to offspring of (PVG x W/F)F1 rats backcrossed to W/F with either RT1u/c (u/c) or RT1u/u) (u/u) phenotype induced high-IgG-alloantibody responses that were associated with acute renal allograft rejection. Likewise, offspring of (PVG x W/F)F1 rats backcrossed to PVG expressing the u/c phenotype had high IgG responses to ACI DSBT associated with acute renal allograft rejection. In contrast, DSBT given to backcrossed recipients expressing the RT1c/c (c/c) phenotype elicited a transient IgM response that switched to a very low IgG response and was associated with renal allograft acceptance. Analysis of IgG isotypes demonstrated that DSBT prevented production of IgG1 and IgG2a, and to a lesser extent IgG2b and IgG2c alloantibodies in c/c but not u/c renal allograft recipients. The differences in the level and isotype of IgG alloantibody responses found in sera of DSBT-pretreated backcross rats of u/c and c/c phenotypes were also present in allograft eluates and splenocyte cultures. Likewise, DSBT-pretreated renal allograft recipients of the c/c phenotype produced lower levels of alloantibodies directed to class I RT1.Aa antigens compared with their u/c counterparts; in contrast, no difference was found in alloantibody responses to class II RT1.Ba antigens. These findings demonstrate that the variable ability of DSBT to enhance renal allograft survival correlates with the inhibition of antidonor class I alloantibody responses of all IgG subclasses by a mechanism that is linked to host MHC.

The effects of donor-specific blood transfusion enhancement of rat renal allografts on host NK cell responses

Donor-specific blood transfusion (DSBT) given 1-2 weeks prior to transplantation prolongs the survival of fully allogeneic ACI (RT1a) renal allografts in PVG (RT1c) recipients from 6-8 days to greater than 100 days. We have previously demonstrated that ACI kidneys transplanted to autologous blood transfusion (ABT)- or DSBT-pretreated PVG recipients stimulated an increase in CD8+ (OX8+) cells in the peripheral blood by 6 days after transplantation. To determine whether this increase represents a general expansion of the entire CD8+ population or only a subpopulation of CD8+ cells, subset analysis was performed on peripheral blood lymphocytes depleted of cells reactive with monoclonal antibodies against rat alpha beta T cell receptor (TCR), CD8, or NK cells (R7.3, OX8, or 3.2.3, respectively). Phenotypic studies of PBL depleted of CD8+ cells demonstrated that all 3.2.3+ NK cells coexpressed CD8; depletion of 3.2.3+ PBL revealed a second subpopulation of CD8+3.2.3- cells comprised predominantly of alpha beta TCR+ T cells. In naive PVG rats the prevalence of these two CD8+ subpopulations was approximately equal. Both ABT- and DSBT-pretreated renal allograft recipients demonstrated a significant and equivalent expansion of the CD8+ cell subpopulation that coexpresses the 3.2.3 NK marker. In contrast, the second subpopulation of CD8+3.2.3- cells did not change significantly after allografting. There were also no differences between DSBT and ABT pretreated rats in activity of PBL against the NK targets YAC-1 and Doxie at 6 days after renal transplantation, though the level of activity was modestly increased compared with naive controls. These findings indicate that renal transplantation in the rat is associated with a significant increase in PBL with the NK phenotype (CD8+3.2.3+) and a modest increase of NK activity, but that DSBT enhancement does not affect this NK cell response.

IgG ALLOANTIBODY RESPONSES TO DONOR-SPECIFIC BLOOD TRANSFUSION IN DIFFERENT RAT STRAIN COMBINATIONS AS A PREDICTOR OF RENAL ALLOGRAFT SURVIVAL1,2

Donor-specific blood transfusion prolongs the survival of fully allogeneic ACI (RT1a) renal allografts in PVG (RT1c) recipients from 7-10 days to greater than 100 days. We have observed significant differences in the alloantibody (Ab1) responses to ACI renal allografts in control and DSBT-treated PVG recipients: DSBT is associated with decreased IgG and IgM alloantibody circulating in serum, deposited in the allograft, and produced in culture by splenocytes. In the present studies the effects of DSBT on alloantibody production and renal allograft survival were extended to examine other recipient strains: F344 (RT1lv1), BN (RT1n), W/F (RT1u) and LEW (RT1l). Animals of each recipient strain were injected i.v. with 0.5 ml of ACI blood alone or followed by a renal allograft. Studies on the kinetics of IgM and IgG alloantibody responses were performed by flow cytometry on lymphocytes from donor ACI, PVG, and PVG.R1 (RT1.Aa class I MHC antigen on PVG background) rats. In F344 and PVG rats, DSBT from ACI rats elicited a transient IgM response that peaked at day 7 and was not followed by a switch to IgG. In control PBS transfused F344 recipients, an ACI renal allograft stimulated both IgM and IgG alloantibody production. DSBT pretreatment significantly decreased circulating IgG alloantibody following ACI renal transplantation and prolonged graft survival in F344 recipients. In DSBT-treated F344 recipients that rejected ACI renal allografts acutely, small amounts of IgG (5-12 mode channel shift) were detected in sera harvested 7 days after transplantation, whereas almost no IgG was detected in the sera from DSBT treated F344 rats that accepted their renal allografts indefinitely. In contrast, DSBT alone from ACI to BN, W/F, or LEW strains elicited a transient IgM response that peaked at day 7 and was followed by a strong IgG response that peaked on days 10-14 and remained high through day 21. DSBT failed to prolong ACI renal allograft survival in any of these strains (survival less than 11 days in control and DSBT rats). The alloantibody response to DSBT in all five recipient strains examined was directed primarily to RT1.Aa class I MHC antigens, as determined by binding studies on lymphocytes from ACI, PVG and PVG.R1 rats and alloantibody blocking studies using biotinylated rat monoclonal antibodies to distinct epitopes of the RT1.Aa antigen. The relative magnitude of blocking of R2/10P and R2/15S binding by sera from BN, W/F, and LEW rats was: control allograft recipients greater than DSBT pretreated allograft recipients greater than DSBT alone.(ABSTRACT TRUNCATED AT 400 WORDS)