Regional release of cyclooxygenase products after radiation exposure of the rat

The present study evaluated the regional release of cyclooxygenase products 4 h following 20 Gy gamma irradiation. Thoracic shielding reduced the radiation-induced increase in immunoreactive thromboxane B2 (iTxB2) excretion to control levels while abdominal shielding partially attenuated the altered excretion of this cyclooxygenase product. To assess the role the kidneys play in the radiation-induced increase in iTxB2 excretion, an in situ isolated perfused rat kidney model was developed. The excretion rate of iTxB2 from irradiated isolated perfused kidneys was not significantly different from sham-irradiated perfused kidneys. Radiation exposure did alter renal cyclooxygenase product release in that the excretion of immunoreactive prostaglandin E2 (iPG2) and immunoreactive 6-keto-PGF1 alpha was significantly increased (P less than 0.05) in irradiated isolated perfused kidneys. These data show that radiation-induced increases in iTxB2 excretion are primarily due to altered extrarenal synthesis and/or metabolism of this arachidonate metabolite.     

Leukotriene F4 and the release of arachidonic acid metabolites from perfused guinea pig lungs in vitro

Radioimmunoassay and bioassay techniques have been used to investigate the ability of leukotriene (LT)F4 to release products of arachidonic acid metabolism from guinea pig isolated lungs perfused via the pulmonary artery. Also, the abilities of LTC4, LTD4, LTE4 and LTF4 to contract guinea pig ileal smooth muscle (GPISM) was studied. Each of the LT's contracted GPISM. The rank order of potency was LTD4 greater than LTC4 greater than LTE4 much greater than LTF4 in a ratio of 1:7:170:280 respectively. Bioassay of pulmonary effluents indicated the passage of LTF4 through the lungs caused a contraction of rabbit aorta as well as an FPL-55712 sensitive contraction of GPISM. The contractions of rabbit aorta were inhibited by pretreatment of the lungs with Indomethacin but not with the thromboxane synthetase inhibitor Dazoxiben. Radioimmunoassay of the lung effluents indicated LTF4 to cause a 70-fold increase in thromboxane B2 (TXB2), 4-fold increase in prostaglandin (PG)E2 and a 16-fold increase in 6-keto PGF1 alpha levels. The LTF4-induced increments of these immunoreactive metabolites was inhibited by pretreatment of the lungs with Indomethacin. Pretreatment of lungs with Dazoxiben inhibited the LTF4-induced increment in TXB2 and enhanced the effluent levels of PGE2 24-fold (compared with untreated lungs). There were no detectable differences in either immunoreactive LTC4 or immunoreactive LTB4 levels. It is concluded LTF4 is a relatively weak agonist on GPISM and can induce the release of cyclooxygenase products of arachidonic acid metabolism from guinea pig perfused lung.     

Effects of leukotriene B4 on permeability, prostacyclin and thromboxane release by normal and oxygen-preexposed isolated, perfused rat lungs

This study assessed the hemodynamic and permeability effects of exogenous, synthetic leukotriene B4 (LTB4) on normal rat lungs and lungs from rats preexposed to oxygen for 48 h, which were isolated and perfused at constant flow in vitro. Adult, Sprague-Dawley rats were exposed to air or greater than 97% O2 for 48 h. After exposure, their lungs were removed from the thorax, ventilated with normoxic gas, and perfused at 12 ml/min with Krebs-Ringer bicarbonate buffer which contained 5 mM glucose and 3 mg/ml albumin. A total of 5.55 micrograms of synthetic LTB4 was infused in three separate boluses over 15 minutes. Perfusion and airway pressures were monitored, and the lungs release of 6-ketoprostaglandin F1 alpha and thromboxane B2 (TXB2) into the effluent from the pulmonary vasculature was measured by radioimmunoassay. The LTB4 had no measureable effects on pulmonary vascular pressures. LTB4 infusion caused a pronounced increase in permeability, indicated by increased albumin concentrations in alveolar lavage fluid from O2-preexposed lungs. Release of TXB2 from both air- and O2-preexposed lungs was increased after LTB4 infusion, while the change in 6-ketoprostaglandin F1 alpha release was not statistically significant. Both the increase in permeability enhanced TXB2 released after LTB4 infusion were inhibited by 10 microM indomethacin in the perfusate. These data indicate that exogenous LTB4 increases microvascular permeability in O2-exposed lungs in association with increased release of TXB2 into the pulmonary vascular effluent.     

Actions of lipoxygenase metabolites in isolated rat lungs

Leukotrienes constrict smooth muscle and could be important for the regulation of the pulmonary circulation. We examined the production and action of lipoxygenase metabolites in isolated lungs, where we controlled the perfusing fluid used. Arachidonate injected into isolated rat lungs perfused with cell- and protein-free physiological salt solution caused a transient pressor response. Following indomethacin, arachidonate caused a delayed slow pressure rise followed by edema. The lung effluent contracted the guinea pig ileum. High-pressure liquid chromatography (HPLC) analysis of the perfusate demonstrated the presence of leukotrienes (LTC4 and LTD4). Diethylcarbamazine, a leukotriene synthesis inhibitor, prevented the slow pressure rise and edema seen after indomethacin plus arachidonate. In lungs perfused with cell- and protein-free physiological salt solution, LTC4, but not LTD4, caused a transient pressure rise followed by a sustained pressure rise. The sustained rise was abolished by a leukotriene-receptor blocker (FPL 55712) but not by indomethacin. In blood-perfused lungs, LTC4 caused only the transient pressure rise that was not blocked by FPL 55712. In lungs perfused with physiological salt solution containing albumin, LTC4 had no effect. We concluded that 1) perfused nonsensitized rat lungs produced LTC4 and LTD4; 2) LTC4 may be a major pulmonary vasoconstrictor; and 3) albumin binding limits the pressor effect of LTC4.     

Protein concentrations have little effect on reabsorption of fluid from isolated rat lungs

A study was conducted to determine whether differences in the concentrations of large molecules between the air space and perfusate solutions altered the rates at which fluid was reabsorbed from isolated fluid-filled perfused rat lungs. Four groups of experiments were conducted: 1) 5 g/dl albumin in the air spaces and perfusate, 2) 15 g/dl albumin in the air space and 5 g/dl albumin in the perfusate, 3) 5 g/dl albumin in the air space and 15 g/dl albumin in the perfusate, and 4) a mixture of 5 g/dl albumin and 7 g/dl Dextran 70 in the air spaces and 5 g/dl albumin in the perfusate. Fluid reabsorption was determined by following the concentration of albumin labeled with Evans blue (T-1824) in the air space and perfusate compartments. Because leakage of protein between the air space and perfusate compartments is very slow, increases in T-1824 concentrations in the air spaces indicated loss of fluid from this compartment, whereas decreases in these concentrations in the perfusate compartment provided evidence of fluid transport into the vasculature. Approximately 30% of the air space fluid was reabsorbed in a 2-h period, and virtually all of this fluid reached the perfusate compartment. Despite oncotic differences that ranged from -65 to 65 Torr, variations in air space or perfusate albumin concentrations did not have a significant effect on this process. A 30% decrease in fluid reabsorption was observed when dextran was in the air space solution, but this decrease did not appear to be due to the oncotic properties of this solution because albumin did not have a measurable effect on reabsorption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary microvascular response to LTB4: effects of perfusate composition

We examined the effects of leukotriene B4 (LTB4) on pulmonary hemodynamics and vascular permeability using isolated perfused guinea pig lungs and cultured monolayers of pulmonary arterial endothelial cells. In lungs perfused with Ringer solution, containing 0.5 g/100 ml albumin (R-alb), LTB4 (4 micrograms) transiently increased pulmonary arterial pressure (Ppa) and capillary pressure (Pcap). Pulmonary edema developed within 70 min after LTB4 injection despite a normal Pcap. The LTB4 metabolite, 20-COOH-LTB4 (4 micrograms), did not induce hemodynamic and lung weight changes. In lungs perfused with autologous blood hematocrit = 12 +/- 1%; protein concentration = 1.5 +/- 0.2 g/100 ml), the increases in Ppa and Pcap were greater, and both pressures remained elevated. The lung weight did not increase in blood-perfused lungs. In lungs perfused with R-alb (1.5 g/100 ml albumin) to match the blood perfusate protein concentration, LTB4 induced similar hemodynamic changes as R-alb (0.5 g/100 ml) perfusate, but the additional albumin prevented the pulmonary edema. LTB4 (10(-11)-10(-6) M) with or without the addition of neutrophils to the monolayer did not increase endothelial 125I-albumin permeability. Therefore LTB4 induces pulmonary edema when the perfusate contains a low albumin concentration, but increasing the albumin concentration or adding blood cells prevents the edema. The edema is not due to increased endothelial permeability to protein and is independent of hemodynamic alterations. Protection at higher protein-concentration may be the result of LTB4 binding to albumin.     

The effects of neutrophils and phospholipase A2 on transvascular albumin flux in isolated rabbit lungs

In this study, addition of phospholipase A2 (PLA2) to salt-perfused isolated rabbit lungs containing rabbit polymorphonuclear leukocytes leads to an increase in pulmonary capillary permeability. We add 1.5 X 10(8) polymorphonuclear leukocytes to the perfusate. Next, indomethacin is added to the perfusate and 40 units of PLA2 are infused into the pulmonary arterial inflow of the lungs. At the end of the study, a lung sample is removed for measurement of transvascular albumin flux using I125-albumin as a measure of the permeability-surface area product. Control studies demonstrate no increase in transvascular albumin flux. Addition of a dual cyclooxygenase and lipoxygenase inhibitor, BW755C, to the perfusate prevents the increase in transvascular albumin flux. We conclude that PLA2 interacts with polymorphonuclear leukocytes to increase protein permeability. Since PLA2 can release endogenous arachidonic acid and platelet-activating factor from cells, this suggests that release of such products may contribute to an increase in pulmonary capillary permeability from polymorphonuclear leukocytes. The ability of BW755C to prevent the increase suggests the possibility that lipoxygenase products contribute.     

Ca(2+) release from ryanodine-sensitive store contributes to mechanism of hypoxic vasoconstriction in rat lungs.

Studies of thapsigargin, cyclopiazonic acid, and ryanodine in isolated pulmonary arteries and smooth muscle cells suggest that release of Ca(2+) from inositol 1,4,5-trisphosphate (IP(3))- and/or ryanodine-sensitive sarcoplasmic reticulum Ca(2+) stores is a component of the mechanism of acute hypoxic pulmonary vasoconstriction (HPV). However, the actions of these agents on HPV in perfused lungs have not been reported. Thus we tested effects of thapsigargin and cyclopiazonic acid, inhibitors of sarcoplasmic reticulum Ca(2+)-ATPase, and of ryanodine, an agent that either locks the ryanodine receptor open or blocks it, on HPV in salt solution-perfused rat lungs. After inhibition of cyclooxygenase and nitric oxide synthase, thapsigargin (10 nM) and cyclopiazonic acid (5 microM) augmented the vasoconstriction to 0% but not to 3% inspired O(2). Relatively high concentrations of ryanodine (100 and 300 microM) blunted HPV in nitric oxide synthase-inhibited lungs. The results indicate that release of Ca(2+) from the ryanodine-sensitive, but not the IP(3)-sensitive, store, contributes to the mechanism of HPV in perfused rat lungs and that Ca(2+)-ATPase-dependent Ca(2+) buffering moderates the response to severe hypoxia.     

Edema from cyclooxygenase products of endogenous arachidonic acid in isolated lung

We infused A23187, a calcium ionophore, into the pulmonary circulation of dextran-salt-perfused isolated rabbit lungs to release endogenous arachidonic acid. This led to elevations in pulmonary arterial pressure and to pulmonary edema as measured by extravascular wet-to-dry weight ratios. The increase in pressure and edema was prevented by indomethacin, a cyclooxygenase enzyme inhibitor, and by 1-benzylimidazole, a selective inhibitor of thromboxane (Tx) A2 synthesis. Transvascular flux of 125I-albumin from vascular to extravascular spaces of the lung was not elevated by A23187 but was elevated by infusion of oleic acid, an agent known to produce permeability pulmonary edema. We confirmed that A23187 leads to elevations in cyclooxygenase products and that indomethacin and 1-benzylimidazole inhibit synthesis of all cyclooxygenase products and TxA2, respectively, by measuring perfusate levels of prostaglandin (PG) I2 as 6-ketoprostaglandin F1 alpha, PGE2, and PGF2 alpha and TxA2 as TxB2. We conclude that release of endogenous pulmonary arachidonic acid can lead to pulmonary edema from conversion of such arachidonic acid to cyclooxygenase products, most notably TxA2. This edema was most likely from a net hydrostatic accumulation of extravascular lung water with an unchanged permeability of the vascular space, since an index of permeability-surface area product (i.e., transvascular albumin flux) was not increased.     

Effects of dextran-bound inhibitors on carbonic anhydrase activity in isolated rat lungs

Effects of macromolecular Prontosil-dextran inhibitors (PD) on carbonic anhydrase (CA) activity in isolated rat lungs were studied. Isolated lungs were perfused with Krebs-Ringer bicarbonate (KRB) solutions containing no inhibitor, PD 100,000 (mol wt 100,000), PD 5,000 (mol wt 5,000), or low-molecular-weight inhibitors (Prontosil or acetazolamide). The time course of effluent perfusate pH equilibration was measured in a stop-flow pH electrode apparatus. Pulmonary CO2 excretion (Vco2) was monitored by continuously recording expired CO2 concentration. The lungs were ventilated with room air and perfused at 37 degrees C with KRB prebubbled with 5% CO2- 20% O2- 75% N2. The results obtained show that both the low-molecular-weight inhibitors and PD's caused postcapillary pH disequilibria (delta pH) in effluent perfusate. However, only acetazolamide and Prontosil caused a reduction in Vco2. These results suggest that there is an intravascular CA, presumably associated with endothelial cell membranes, that is accessible to all inhibitors used and is responsible in part for equilibration of the CO2- HCO3- -H+ reactions in the perfusate but, under the conditions used, does not affect CO2 excretion; and there is an extravascular (possibly intracellular) CA that can be inhibited by low-molecular-weight inhibitors, is primarily responsible for enhanced CO2 transfer across the alveolar-capillary barrier (perhaps via facilitation of CO2 diffusion), and is in part responsible for pH equilibration.     

Alpha-thrombin-induced pulmonary vasoconstriction

We examined the direct effects of thrombin on pulmonary vasomotor tone in isolated guinea pig lungs perfused with Ringer albumin (0.5% g/100 ml). The injection of alpha-thrombin (the native enzyme) resulted in rapid dose-dependent increases in pulmonary arterial pressure (Ppa) and pulmonary capillary pressure (Ppc), which were associated with an increase in the lung effluent thromboxane B2 concentration. The Ppa and Ppc responses decreased with time but then increased again within 40 min after thrombin injection. The increases in Ppc were primarily the result of postcapillary vasoconstriction. Pulmonary edema as evidenced by marked increases (60% from base line) in lung weight occurred within 90 min after thrombin injection. Injection of modified thrombins (i.e., gamma-thrombin lacking the fibrinogen recognition site or i-Pr2P-alpha-thrombin lacking the serine proteolytic site) was not associated with pulmonary hemodynamic or weight changes nor did they block the effects of alpha-thrombin. Indomethacin (a cyclooxygenase inhibitor), dazoxiben (a thromboxane synthase inhibitor), or hirudin (a thrombin antagonist) inhibited the thrombin-induced pulmonary vasoconstriction, as well as the pulmonary edema. We conclude that thrombin-induced pulmonary vasoconstriction is primarily the result of constriction of postcapillary vessels, and the response is mediated by generation of cyclooxygenase-derived metabolites. The edema formation is also dependent on activation of the cyclooxygenase pathway. The proteolytic site of alpha-thrombin is required for the pulmonary vasoconstrictor and edemogenic responses.     

Effects of pregnancy, oxytocin, ovine trophoblast protein-1 and their interactions on endometrial production of prostaglandin F2 alpha in vitro in perifusion chambers

Pregnancy and intrauterine infusion of ovine trophoblast protein one (oTP-1) decrease oxytocin-induced secretion of prostaglandin F2 alpha (PGF) from the uterus. In the present study, effects of oTP-1 and pregnancy on endometrial secretion of PGF were examined in an in vitro perifusion system. In Experiment 1, endometrium from day 14 pregnant and cyclic ewes was perifused sequentially on both the lumenal and myometrial sides with Krebs Ringers Bicorbonate solution (KRB), KRB plus oxytocin (1 IU/ml) and KRB alone. Endometrium from pregnant ewes secreted more PGF from both lumenal and myometrial sides than endometrium from cyclic ewes (P less than 0.05). Oxytocin stimulated secretion of PGF from both sides of endometrium regardless of status. Secretion of PGF was greater from the lumenal surface of endometrium compared to myometrium (P less than 0.05) for pregnant and cyclic ewes. For Experiment 2, endometrium was collected from day 15 cyclic ewes and perifused sequentially with KRB, KRB plus 300 ng/ml of either Bovine Serum Albumin (BSA) or oTP-1, KRB with or without BSA or oTP-1 plus oxytocin (1 IU/ml) and then KRB alone. Oxytocin stimulated greater release of PGF from oTP-1-treated than BSA-treated endometrium. Pretreatment of endometrium with oTP-1 had the same effect on oxytocin-induced PGF secretion as cotreatment with oTP-1 and oxytocin. In Experiment 3, uterine horns of cyclic ewes were catheterized on day 10 of the estrous cycle, and infused with either oTP-1 or day 16 pregnant sheep serum proteins on days 12, 13 and 14. Endometrium was collected on day 15 and perifused sequentially with KRB, KRB plus oxytocin (1 IU/ml) and then KRB alone. Treatment of ewes with oTP-1 attenuated endometrial secretion of PGF in response to oxytocin. Results of this study indicate that: (1) pregnancy stimulates basal secretion of PGF from endometrium and has no effect on oxytocin-induced secretion of PGF in vitro; (2) short-term oTP-1 treatment enhances oxytocin-induced PGF secretion from day 15 cyclic endometrium and (3) long-term oTP-1 treatment in vivo inhibits oxytocin-induced PGF secretion in ewes.     

Effects of pregnancy, oxytocin, ovine trophoblast protein-1 and their interactions on endometrial production of prostaglandin F2α in vitro in perifusion chambers

Pregnancy and intrauterine infusion of ovine trophoblast protein one (oTP-1) decrease oxytocin-induced secretion of prostaglandin F2α (PGF) from the uterus. In the present study, effects of oTP-1 and pregnancy on endometrial secretion of PHF were examined in an in vitro perifusion system. In Experiment 1, endometrium from day 14 pregnant and cyclic ewes was perifused sequentially on both the lumenal and myometrial sides with Krebs Ringers Bicorbonate solution (KRB), KRB plus oxytocin (1 IU/ml) and KRB alone. Endormetrium pregnant ewes secreted more PGF fro both lumenal and myotrial sides than endometrium from cyclic ewes (P<0.05). Oxytocin stimulated secretion of PGF was greater from the lumenal surface of endometrium compared to myometrium was collected from day 15 cyclic ewes and perifused sequentially with KRB, KRB plus 300 ng/ml of either Bovine Serum Albumin (BSA) or oTP-1, KRB with or without BSA or oTP-1 plus oxytocin (1 IU/ml) and then KRB alon. Oxytocin stimulated greater release of PGF from oTP-1-treated than BSA-treated endometrium. Pretreament of endometrium with oTP-1 has the same effect on oxytocin-induced PGF section was cotreatment with oTP-1 and oxytocin. In Experiment 3, uterine horns of cyclic ewes were catheterized on day 10 of the estrous cycle, and infused with either oTP-1 or day 16 pregnant sheep serum proteins on days 12, 13 and 14. Endometrium was collected on day 15 and perifused sequentially with KRB, KRB plus oxytocin (1 IU/ml) and then KRB alone. Treatment of ewes with oTP-1 attenuated endometrial secretion of PGF in response to oxytocin. Results of this study indicate that: (1) preganancy stimulates basal secretion of PGF from endometrium and has no effect on oxytocin-induced secretion of PGF in vitro; (2) short-term oTP-1 treatment enhances oxytocin-induced PGF secretion from day 15 cyclic endometrium and (3) long-term oTP-1 treatment in vivo inhibits oxytocin-induced PGF secretion in ewes.     

Plasma protein binding and endothelial enzyme interactions in the lung

The influence of plasma albumin binding of the synthetic angiotensin-converting enzyme (ACE) substrate [3H]benzoyl-phenylalanyl-alanyl-proline (BPAP) on BPAP hydrolysis by pulmonary endothelial ACE was studied in isolated rabbit lungs perfused with a salt solution containing either 5% bovine serum albumin (BSA) or 5% dextran. The single-pass indicator-dilution method was used to measure the fraction (M) of [3H]BPAP hydrolyzed. Lung M was greater with albumin-free perfusate than when BSA was present. M decreased as the time (ti) that the BPAP was in contact with the BSA before reaching the lung was increased, suggesting that some BSA binding sites for BPAP were not in equilibrium during bolus transit through the lungs. The M vs. ti data were correlated using a model incorporating both rapid and slow binding kinetics of BPAP and BSA. For the slow BPAP-BSA interaction, the dissociation rate constant was approximately 0.015 s-1, and the fraction of the BPAP bound to these slowly equilibrating sites at equilibrium was approximately 22%. The results indicate that transient plasma protein binding kinetics can affect lung BPAP hydrolysis.     

Increased pulmonary vascular resistance and permeability due to arachidonate metabolism in isolated rabbit lungs

Liberation and metabolism of arachidonic acid may be the common final pathway of different stimuli on the pulmonary vascular bed. In a model of isolated, ventilated rabbit lungs, perfused with Krebs Henseleit albumin buffer in a recirculating system, changes of pulmonary vascular resistance and of vascular permeability are monitored continuously. The addition of free arachidonic acid or of the Ca-ionophore A 23187 to the perfusion fluid consistently evokes a biphasic increase in vascular resistance as well as an initially reversible increase in vascular permeability, followed by pulmonary edema. Both phases of increased vascular resistance are completely suppressed by inhibition of the cyclooxygenase, decreased to a large degree by inhibitors of thromboxane synthetase, and markedly augmented by short preincubation of arachidonic acid with ram seminal vesicular microsomes and by sulfhydryl reagents. The increased pulmonary vascular permeability is augmented by inhibition of cyclooxygenase and reduced by simultaneous lipoxygenase inhibition. Antagonists of histamine, serotonin and sympathic or parasympathic activity do not have any influence. PG F2alpha., TxB2, PG E2 and PG I2 alter the pulmonary vascular resistance, but do not increase vascular permeability. In conclusion, increased availability of free arachidonic acid evokes a rise in pulmonary vascular resistance, which can be ascribed to cyclooxygenase products, especially to thromboxane, and causes a rise in vascular permeability which can be ascribed to lipoxygenase products. The findings may be related to acute pulmonary lesions with increase in vascular resistance and with vascular leakage.     

The metabolism of arachidonic acid in isolated perfused fetal and neonatal rabbit lungs

The developmental pattern of fetal and neonatal rabbit lungs to metabolize arachidonic acid (AA) to different cyclo-oxygenase products was studied in isolated rabbit lungs, which were perfused with Krebs bicarbonate buffer. 14C-AA (66 nmol) was injected into the pulmonary circulation and the nonrecirculating perfusion effluent was collected for four minutes. About ten per cent of the injected radioactivity was found in the 0-4 min perfusion effluent. The metabolites of AA in the effluent were analyzed by thin layer chromatography. The major metabolites of AA were PGE2 and its 15-keto-derivates, but also PGF2 alpha and its 15-keto-derivates, TXB2 and 6-keto-PGF1 alpha were found in the effluent. The most drastic developmental change was the increase in the amount of 15-keto-metabolites of PGE2 from late fetal period to the lungs of one day old rabbits (1.8 fold increase between birth and first postnatal day). Smaller changes were detected in the amounts of other cyclo-oxygenase products.     

Prostaglandins potentiate U-46619-induced pulmonary microvascular dysfunction.

The induction of cyclooxygenase is an important event in the pathophysiology of acute lung injury. The purpose of this study was to examine the synergistic effects of various cyclooxygenase products (PGE(2), PGI(2), PGF(2alpha)) on thromboxane A(2) (TxA(2))-mediated pulmonary microvascular dysfunction. The lungs of Sprague-Dawley rats were perfused ex vivo with Krebs-Henseleit buffer containing indomethacin and PGE(2) (5 x 10(-8) to 1 x 10(-7) M), PGF(2alpha) (7 x 10(-9) to 5 x 10(-6) M), or PGI(2) (5 x 10(-8) to 2 x 10(-5) M). The TxA(2)-receptor agonist U-46619 (7 x 10(-8) M) was then added to the perfusate, and then the capillary filtration coefficient (K(f)), pulmonary arterial pressure (Ppa), and total pulmonary vascular resistance (RT) were determined. The K(f) of lungs perfused with U-46619 was twice that of lungs perfused with buffer alone (P = 0.05). The presence of PGE(2), PGF(2alpha), and PGI(2) within the perfusate of lungs exposed to U-46619 caused 118, 65, and 68% increases in K(f), respectively, over that of lungs perfused with U-46619 alone (P < 0.03). The RT of lungs perfused with PGE(2) + U-46619 was approximately 30% greater than that of lungs exposed to either U-46619 (P < 0.02) or PGE(2) (P < 0.01) alone. When paired measurements of RT taken before and then 15 min after the addition of U-46619 were compared, PGI(2) was found to attenuate U-46619-induced increases in RT (P < 0.01). These data suggest that PGE(2), PGI(2), and PGF(2alpha) potentiate the effects of TxA(2)-receptor activation on pulmonary microvascular permeability.     

The isolated perfused rabbit ovary — A model for studies of ovarian function

Summary In the present investigation the ultrastructure of isolated rabbit ovaries, perfused with different media for various time periods, was studied. The steroid hormone production by the perfused ovary was also determined. Perfusion with Medium 199 results in prominent interstitial ovarian oedema which increases with perfusion time. Even after the addition of 6–10 % Dextran T40, oedema appears in the interstitial tissue of the ovary. Perfusion solutions with osmotically active colloid particles of large molecular size (Dextran T70; average molecular weight 70,000 and bovine serum albumin), cause less distortion in the ovarian structure, and ultrastructurally the ovarian tissues appear essentially the same as in the control ovaries.The results indicate that the perfused rabbit ovary, under strictly controlled conditions, can be used as an experimental model for studies of various aspects of ovarian function, including follicular rupture.     

Acute pneumonia reversibly inhibits hypoxic vasoconstriction in isolated rat lungs.

Pneumonia was induced in rats by instillation of carrageenin (0.5 ml of 0.7% solution) into the trachea. Three or four days after instillation, the lungs were isolated, perfused with blood of healthy rat blood donors, and ventilated with air + 5% CO2 or with various hypoxic gas mixtures. Pulmonary vascular reactivity to acute hypoxic challenges was significantly lower in lungs of rats with pneumonia than in lungs of controls. The relationship between O2 concentration in the inspired gas and Po2 in the blood effluent from the preparation was shifted significantly to lower Po2 in lungs with pneumonia compared to control ones. These changes were not present in rats allowed to recover for 2-3 weeks after carrageenin instillation. We suppose that blunted hypoxic pulmonary vasoconstriction may contribute to hypoxaemia during acute pulmonary inflammation. Decreased Po2 in the blood effluent from the isolated lungs with pneumonia implies significant increase of oxygen consumption by the cells involved in the inflammatory process.     

Leukotriene E4 causes pulmonary vasoconstriction, not inhibited by meclofenamate

Leukotriene E4 (LTE4) appears to be a rather stable product of the lipoxygenase pathway. Its action in the pulmonary circulation is unknown. Therefore we investigated its effect on the circulation of isolated rat lungs perfused with a cell- and plasma-free solution. Synthetic LTE4 in doses from .15 micrograms to 5 micrograms/.25 ml .9% NaCl injected as a bolus in the pulmonary artery during normoxia caused a fast, transient perfusion pressure increase within seconds. This was followed by a slow rise in baseline perfusion pressure (normoxia) over 25 min. In addition, 5 micrograms LTE4 caused edematogenic lung damage. Injection of 1.5 micrograms LTE4 during hypoxic vasoconstriction caused fast, transient pressure rises, similar to normoxic conditions. 6-keto-PGF1 alpha and TXB2 were measured in the lung effluent before and after LTE4 injection. Neither 6-keto-PGF1 alpha nor TXB2 production changed after LTE4 injection. Meclofenamate (.5 micrograms/ml) increased the fast, transient and the slow, sustained pressure rise. We conclude that LTE4 caused direct pulmonary vasoconstriction unrelated to cyclooxygenase products.