The role of the adrenal gland in control of H+ and NH4+ excretion by toad urinary bladder

The urinary bladder of Bufo marinus has been shown to excrete H+ and NH4+ and this excretion is increased by metabolic acidosis. The involvement of the adrenal gland and its steroid secretions in the adaptation for increased acid and ammonia excretion by the bladder was tested during the course of this study. Groups of toads were adrenalectomized and maintained in chronic NH4Cl-induced acidosis. Three other groups of toads were adrenalectomized and put in acidosis but repleted with 2.5 mg/day of either cortisol (CT), dexamethasone (Dexa), or deoxycorticosterone acetate (DOCA). All control groups were sham-operated. The bladders were excised after 3 days and mounted between 2-ml Lucite chambers. Net H+ and NH4+ fluxes into the mucosal media were measured and reported in units of nanomoles per 100 mg bladder per minute. In control acidotic toads H+ excretion was 20.1 +/- 2.0 and the adrenalectomized nonreplete group H+ excretion was 14.2 +/- 1.87 (P less than 0.04). For the same groups NH4+ excretion was 2.90 +/- 0.26 for the controls and 1.38 +/- 0.19 for the adrenalectomized (P less than 0.001). The H+ excretion in CT-, Dexa-, and DOCA-repleted toads was not significantly different from the control group. NH4+ excretion, however, showed a 55% decrease (P less than 0.001) in the CT group, and a 45% decrease (P less than 0.05) in the Dexa group. The NH4+ excretion in the DOCA repleted group was significantly different from the control group. Therefore, we conclude that the adrenal gland plays a role in the adaptive increase of H+ and NH4+ excretion by the urinary bladder in acidosis through the secretion of steroid hormones. The increase in NH4+ excretion appears to be a mineralocorticoid-stimulated process. We were not able to determine in this study if the steroid hormones had an exacting regulatory role or one of a permissive role over H+ and NH4+ excretion in the toad urinary bladder.     

Insulin-mediated H+ and NH+4 excretion in the urinary bladder of Bufo marinus

This study was done to determine if insulin mediates H+ and NH+4 excretion in the urinary bladder of Bufo marinus. Acidosis was induced by gavaging with 10 ml of 120 mM NH4Cl 3X daily for 2 days. Hemibladders were mounted between Lucite chambers. Insulin (porcine) was added to the serosal solution of the experimental bladder (10(2) mU/ml). After a 15-min equilibration the flux was measured for 2 hr. H+ excretion was measured from change in pH of the mucosal fluid and the NH+4 measured colorimetrically. The excretion was normalized for weight of bladder and reported in units of nanomoles (100 mg bladder)-1(min)-1. Plasma insulin was determined by radioimmunoassay and glucose by the glucose oxidase method. In 14 control bladders H+ excretion was 8.75 +/- 1.28 and experimental was 16.35 +/- 2.50 (P less than 0.025), while NH+4 excretion in control bladder was 3.29 +/- 0.95 and experimental was 6.58 +/- 1.89 (P less than 0.01). This response was absent when the insulin was heat inactivated (P greater than 0.2 and P greater than 0.3 respectively). Plasma insulin-like levels in 10 normal toads was 0.57 +/- 0.16 ngm/ml and in acidotic toads 1.25 +/- 0.16 ng/ml (P less than 0.025). Plasma glucose levels in 10 normal toads were 22.0 +/- 3.5 mg/dl and in 12 acidotic toads 17.8 +/- 0.75 mg/dl (P less than 0.025). We conclude that plasma insulin is increased in acidosis and that insulin stimulates excretion of H+ and NH+4 in the toad urinary bladder.     

Prostaglandin (PG) analysis in urine of humans and rats by different radioimmunoassays: effect on PG-excretion by PG-synthetase inhibitors, laparotomy and furosemide.

The radioimmunological (RIA) determination of prostaglandin (PG) E2 and of PGF2alpha in urine of humans and rats is described in detail. After extraction and chromatography PGE2 was determined by using a PGE specific antibody or by using either PGB or PGF2alpha specific antibodies after the respective conversion procedures. The three different RIA procedures were compared to each other. PGF2alpha was determined by a specific antibody to PGF2alpha. Basal excretion of PGE2 and of PGF2alpha in healthy women on free diet was 9.3 ng/hour+/-0.98 and 18.3 ng/hour +/- 2.5 respectively. Furosemide increased the excretion of PGE2 and of PGF2alpha in humans significantly, while PG-excretion rates decreased on indomethacin. In rat urine PGE2 and PGF2alpha increased markedly from 46.2 pg/min +/- 9.3 and 27+/- 3.4 to 253.8 +/- 43.3 and 108 +/- 12.6 pg/min (per one kidney) in the anesthetized-laparotomized animal. This increase was abolished after giving two different PG synthetase inhibitors.     

Antiabortifacient action of dibenzyloxyindanpropionic acid in mice

To evaluate the details of the adrenergic stimulation of urinary prostaglandins in man, ten normal volunteers were given various agonists and antagonists. The effect of 4 hour IV infusions of norepinephrine (NE), NE + phentolamine (PHT), NE + phenoxybenzamine (PHB), NE + prazosin (PZ), isoproterenol (ISO), and PHT alone on urinary PGE2 and PGI2 (6 keto PGF1 alpha) were determined. PGE2 and 6 keto PGF1 alpha were measured by radioimmunoassay from 4 hour urine samples. NE stimulated both PGE2 (196 +/- 40 to 370 +/- 84 ng/4 hrs/g creatinine and 6 keto PGF1 alpha (184 +/- 30 to 326 +/- 36), both p less than 0.01. In contrast, ISO had no effect on either PGE2 or 6 keto PGF1 alpha excretion. Alpha blockade with PHT. PHB, or PZ inhibited the NE induced systemic pressor effect. However, the effect of the alpha blockers on the NE induced stimulation of PGE2 and 6 keto PGF1 alpha varied. PHT did not alter the NE stimulated PGE2 or 6 keto PGF1 alpha release (370 +/- 84 vs. 381 +/- 80) PGE2 and (326 +/- 50 vs. 315 +/- 40) 6 keto PGF1 alpha both p greater than 0.2). PHT alone stimulated only 6 keto PGF1 alpha. PHB and the specific alpha 1 antagonist PZ similarly eliminated the NE induced prostaglandin release. These results suggest that adrenergically mediated urinary prostaglandin release in man is via an alpha receptor with alpha 1 characteristics.     

Determination of prostaglandin F2 alpha, E2, D2 and 6-keto-F1 alpha in human cerebrospinal fluid.

Prostaglandin (PG)F2 alpha, E2, D2 and 6-keto-F1 ALha were determined in human cerebrospinal fluid by a mass spectrometric technique. The samples were obtained from 12 patients with suspected intracranial disease. A 64 fold variation in PG levels was observed. The major PG was 6-keto-F1 alpha (0.12--15 ng/ml). PGF2 alpha and PGE2 were present in lower concentrations PGD2 was below the level of detection (0.05 ng/ml) except in one patient with extremely high total levels of PGs.     

Characterization of prostaglandin (PG)-binding sites expressed on human basophils. Evidence for a prostaglandin E1, I2, and a D2 receptor.

Recent data suggest that prostaglandins (PGs) are involved in the regulation of basophil activation. The aim of this study was to characterize the basophil PG-binding sites by means of radioreceptor assays using 3H-labeled PGs. Scatchard analysis for pure (greater than 95%) chronic myeloid leukemia (CML) basophils revealed two classes of PGE1-binding sites differing in their affinity for the natural ligand (Bmax1 = 217 +/- 65 fmol/10(8) cells; Kd1 = 0.5 +/- 0.2 nM; Bmax2 = 2462 +/- 381 fmol/10(8) cells; Kd2 = 47 +/- 20 nM; IC50 = PGE1 less than PGI2 less than PGD2 less than PGE2 less than PGF2 alpha) as well as two classes of PGI2 (iloprost)-binding sites (Bmax1 = 324 +/- 145 fmol/10(8) cells; Kd1 = 0.5 +/- 0.3 nM; Bmax2 = 2541 +/- 381; Kd2 = 27 +/- 6 nM; IC50 = PGI2 less than PGE1 less than PGD2 less than PGE2 less than PGF2 alpha. In addition, CML basophils exhibited a single class of PGD2-binding sites (Bmax = 378 +/- 98 fmol/10(8) cells; Kd = 13 +/- 4 nM; IC50: PGD2 less than PGI2 less than PGE1 less than PGE2 less than PGF2 alpha). In contrast, we were unable to detect specific saturable PGE2-binding sites. Primary and immortalized (KU812) CML basophils revealed an identical pattern of PG receptor expression. Basophils (KU812) expressed significantly (p less than 0.001) lower number of PGE1 (PGI2)-binding sites (Bmax1: 9% (20%) of control; Bmax2: 36% (50%) of control) when cultured with recombinant interleukin 3 (rhIL-3), a basophil-activating cytokine, whereas rhIL-2 had no effect on PG receptor expression. Functional significance of binding of PGs to basophils was provided by the demonstration of a dose-dependent increase in cellular cAMP upon agonist activation, with PGE1 (ED50 = 1.7 +/- 1.1 nM) and PGI2 (ED50 = 2.8 +/- 2.3 nM) being the most potent compounds. These findings suggest that human basophils express specific receptors for PGE1, PGI2 as well as for PGD2.     

The biosynthesis of the 3-series prostaglandins in rat uterus after alpha-linolenic acid feeding: Mass spectroscopy of prostaglandins E and F produced by rat uteri in tissue culture

The abnormal uterine activity associated with dietary n-3 fatty acids may result from competitive inhibition of PG2 production. Uterine synthesis of 2- and 3-series prostaglandins F(PGF) and E(PGE) was studied using mass spectrophotometry in rats fed diets containing predominantly n-3 fatty acid, n-6 fatty acid, or control pelleted diet. Mass spectra of PGF (Me, TMS and Me, TBDMS derivatives) synthesised by uteri of n-3 fed rats were characterised by 8 ions containing the n-3 double bond, and m.i.d. of the 651/653 ions of PGF-Me, TBDMS indicated PGF3 alpha synthesis (44 +/- 8% and 13 +/- 2% of PGF release by uteri incubated + or -5 micrograms/ul calcium ionophore A23187 respectively). In uteri from the control diet group incubated with ionophore, PGF3 alpha ions were detected and PGF 3 alpha represented 9.5 +/- 1.0% of PGF alpha release. Similarly, analysis of PGE from uteri of n-3 fed rats indicated that PGE3 (16 +/- 6% of PGE) was released in the presence of ionophore A23187. Synthesis of 3-series PG by rat uteri was detected after only 3 weeks of n-3 diet. The capacity to synthesise 3-series PG increased at intracellular calcium concentrations which mimicked cell calcium during decidual autolysis at parturition. These experiments suggest that uterine synthesis of 3-series PG is regulated by the specifity of enzymes incorporating fatty acids, rather than by the cyclooxygenase enzyme.     

Effect of platelet activating factor on prostaglandin release from ovine endometrial cells in culture

Platelet activating factor (PAF) added in vitro to ovine endometrial cells in primary culture caused a dose-dependent increase in the release of prostaglandin (PG) E into the medium compared with release from untreated cells. At a concentration of 1000 ng/ml of PAF, PGE levels in treatment dishes were significantly higher (P less than 0.05) than those in control dishes [130 +/- 8% vs 100% (mean +/- SEM, N = 5 ewes)]. PAF did not alter the release of PGF2 alpha by the same cells. By contrast, the ovine trophoblast interferon, ovine trophoblast protein-1 (oTP-1, 1 ng/ml) attenuated the release of both PGE and PGF2 alpha and this was not overcome by the presence of PAF (100 ng/ml). Thus does not appear that PAF contributes to the antiluteolytic signal in sheep by a direct action on release of PGF2 alpha although it could influence implantation via stimulation of PGE.     

Phospholipid changes during adaptation to acidosis in urinary bladder of Bufo marinus

The purpose of this study was to determine whether phospholipids (PL) play a role in the adaptation to metabolic acidosis by toad urinary bladder epithelium. Toads were placed in an NH4Cl acidosis for 48 hr. Quarter bladders were removed and incubated with [32P]orthophosphate or [3H]arachidonic acid for 1 hr at 25 degrees C. PL were detected by thin layer chromatography, autoradiography, and quantitated by liquid scintillation counting or fractional amounts were determined from phosphate content and expressed as counts per minute per micromolar of total phosphate or as percentage of fraction of total PL. Incorporation of [3H]arachidonic acid into urinary bladder PL was measured in acidotic and normal toads. There was a higher rate of arachidonic acid incorporation into several PL in acidotic animals. Phosphatidic acid and phosphatidylserine fraction in acidosis was 37,705 +/- 6,821 and in normal bladders was 9,254 +/- 2,652 (P less than 0.005); phosphatidylcholine fraction in acidotic toads was 80,462 +/- 16,862 and in normal bladders was 26,892 +/- 5,198 (P less than 0.025); and the phosphatidylethanolamine (PE) fraction in acidotic was 48,665 +/- 10,998 and in normal animals was 17,441 +/- 3,905 (P less than 0.025). 32P labeling revealed a higher rate of incorporation in bladders from acidotic toads compared with normal toads. In the acidotic bladders, the phosphatidic acid and phosphatidylserine fraction was 19,754 +/- 3,597 and in normal bladders was 12,980 +/- 1,394 (P less than 0.05) and for PE acidotic bladders was 9,129 +/- 1,304 and in normal bladders was 3,285 +/- 416 (P less than 0.001). Fractional PL (reported as percentage of fraction of total PL based on total lipid phosphorus) analysis in normal toads revealed phosphatidylinositol = 8.1 +/- 0.6% and PE = 27 +/- 1.2%, whereas for acidotic toads phosphatidylinositol = 11 +/- 0.6% and PE = 32 +/- 1.0% (P less than 0.01 for both). Aldosterone, a known stimulator of acidification, had no effect on 32P incorporation into PL fractions of the bladder. The increase in PL turnover following induction of acidosis is consistent with increased membrane synthesis or turnover during metabolic acidosis and this may reflect an increased transport of vesicular H+-ATPase into the apical membrane or the result of a proliferation of acid-secreting mitochondria-rich cells or both.     

Activity of phospholipase C in ovine luteal tissue in response to PGF2 alpha, PGE2 and luteinizing hormone.

Four ewes were utilized to determine the effects of prostaglandin (PG) F2 alpha, PGE2 and luteinizing hormone (LH) on activity of phospholipase C (PLC) in ovine luteal tissue. Corpora lutea were collected on d 10 post-estrus and six slices from one corpus luteum from each ewe were pre-incubated with [3H]-inositol prior to incubation with one of 6 treatments. Treatments were 1) control, 2) PGF2 alpha (100 ng/ml), 3) PGE2 (10 ng/ml), 4) LH (10 ng/ml), 5) PGF2 alpha + PGE2 and 6) PGF2 alpha + LH. Phospholipase C was determined indirectly by measuring the accumulation of [3H]-inositol mono-, bis- and tris-phosphates (IP, IP2, IP3). Effects of PGF2 alpha (0 vs. PGF2 alpha) and luteotropic treatment (0 vs. PGE2 vs. LH) and their interactions were determined by analysis of variance. There was a significant main effect of PGF2 alpha (P less than 0.01) as concentrations of IP, IP2, IP3 and total [3H]-inositol phosphates were greater in tissue slices treated with PGF2 alpha, regardless of luteotropic treatment. Within groups receiving no PGF2 alpha (1,3,4), no effect of luteotropic treatment was observed. Within groups receiving PGF2 alpha (2,5,6), LH caused a significant (P less than .05) increase in the accumulation of total [3H]-inositol phosphates. Thus, PGF2 alpha can stimulate the activity of PLC in ovine luteal tissue and LH can potentiate this effect.     

The urinary excretion of prostaglandins and thromboxane B2 in healthy volunteers: a study in males and females, and on the influence of seminal fluid contamination

Radioimmunoassay measurements of prostaglandins (PGs) E2, F2 alpha, 6-keto-PGF1 alpha and thromboxane (Tx) B2 in 24 h urine specimens from a male and a female healthy volunteer on several consecutive days revealed a dramatic increase of PGE2, PGF2 alpha, 6-keto-PGF1 alpha on days, upon which they had sexual intercourse; only TxB2 remained stable. Furthermore, the PGE2/PGF2 alpha ratio rose to values greater than 0.5 on days with sexual intercourse. This was found to be due to contamination of the urine samples by seminal fluid. Two 24 h urine samples from each of 26 healthy male and female volunteers (HV) revealed higher (p less than 0.01) mean PGE2 and PGF2 alpha values in males than in females. The results show that the interpretation of the urinary PG excretion as a measure of renal PG synthesis should be considered carefully, and that a PGE2/PGF2 alpha ratio greater than 0.5 indicates probable seminal contamination of urine.     

Evidence for an extra-renal origin of urinary prostaglandin E2 in healthy men

In order to verify the validity of the assumption that male urinary Prostaglandin (PG) E2 reflects its renal production, PGE2 and PGF2 alpha concentrations were measured by radioimmunoassay in the renal venous plasma (RVP) and urine (U) of 12 male and 4 female healthy volunteers. While women had a similar PGE2/PFG2 alpha ratio in RVP (0.59 +/- 0.18) and U (0.41 + 0.06), men and a significantly (P less than 0.05) higher ratio in U (1.43 +/- 1.72) as compared to RVP (0.54 +/- 0.16). This was largely due to considerably higher and more variable U-PGE1 concentrations (roughly 6 times higher than female values), despite almost identical RVP levels. The possibility of an increased U excretion of a cross-reacting member of the PG-system, as a cause of such apparently high PGE2-like immunoreactivity (LI), was ruled out by TLC characterization of PGE2-LI with three different anti-PGE1 sera. Thus, male U-PGE2 may variably reflect an extra-renal source, such as contamination with trace amounts of seminal fluid. It is concluded that, unless such a contamination can be monitored and corrected for, measurement of male U-PGE1 should be considered of questionable relevance to renal PG-synthesis.     

Prostaglandin synthesis by the cochlea

The exogenous and endogenous syntheses of prostaglandins (PG's) by the cochlea of adult mongolian gerbils were studied in vitro. After incubation of the whole membraneous cochlea with [3H]-arachidonic acid (AA), syntheses of PGF2 alpha, 6-keto PGF1 alpha, PGE2, thromboxane (TX) P2 and PGD2 were evidenced in this order. The synthesis of radioactive PG's was almost completely inhibited by incubation with 10(-5) M indomethacin. No significant amounts of those PG's were detected by radioimmunoassay (RIA) in the cochlea obtained from animals killed by microwave irradiation at 5.0 kw for 0.8 sec. However, when the homogenate of the whole membraneous cochlea obtained from animals without microwave irradiation was incubated at 37 degrees C for 0-15 min, PGD2, PGE2, PGF2 alpha and 6-keto PGF1 alpha were found to be formed from endogenous AA in the cochlea by RIA. PG's were formed already at 0 time to considerable level (PGD2, PGF2 alpha and 6-keto PGF1 alpha, 90-120 pg/cochlea; PGE2, 370 pg/cochlea), reached to the maximum level (PGD2, PGF2 alpha and 6-keto PGF1 alpha, 170-200 pg/cochlea; PGE2, 500 pg/cochlea) at a 5-min incubation, and then gradually decreased. On the other hand, the amount of TXB2 was lower than the detection limit by RIA (less than 50 pg/cochlea) even after the incubation. The cochlea was dissected into three parts: organ of Corti + modiolus (OC + M), lateral wall (LW), and cochlear nerve (CN), and then PG's formed by these tissues were determined after a 5-min incubation of the homogenates. In the CN and OC + M, PGE2 was the major PG (100 and 160 pg/tissue, respectively), and the amounts of PGD2, PGF2 alpha and 6-keto PGF1 alpha were about 1/3 of those of PGE2. In the LW, the amounts of PGD2, PGE2, PGF2 alpha and 6-keto PGF1 alpha were about the same level (70-100 pg/LW).     

Intraluteal infusions of prostaglandins of the E, D, I, and A series prevent PGF2 alpha-induced, but not spontaneous, luteal regression in rhesus monkeys

A luteotropic role for prostaglandins (PGs) during the luteal phase of the menstrual cycle of rhesus monkeys was suggested by the observation that intraluteal infusion of a PG synthesis inhibitor caused premature luteolysis. This study was designed to identify PGs that promote luteal function in primates. First, the effects of various PGs on progesterone (P) production by macaque luteal cells were examined in vitro. Collagenase-dispersed luteal cells from midluteal phase of the menstrual cycle (Day 6-7 after the estimated surge of LH, n = 3) were incubated with 0-5,000 ng/ml PGE2, PGD, 6 beta PGI1 (a stable analogue of PGI2), PGA2, or PGF2 alpha alone or with hCG (100 ng/ml). PGE2, PGD2, and 6 beta PGI1 alone stimulated (p less than 0.05) P production to a similar extent (2- to 3-fold over basal) as hCG alone, whereas PGA2 and PGF2 alpha alone had no effect on P production. Stimulation (p less than 0.05) of P synthesis by PGE2, PGD2, and 6 beta PGI1 in combination with hCG was similar to that of hCG alone. Whereas PGA2 inhibited gonadotropin-induced P production (p less than 0.05), that in the presence of PGF2 alpha plus hCG tended (p = 0.05) to remain elevated. Second, the effects of various PGs on P production during chronic infusion into the CL were studied in vivo. Saline with or without 0.1% BSA (n = 12), PGE2 (300 ng/h; n = 4), PGD2 (300 ng/h; n = 4), 6 beta PGI1 (500 ng/h; n = 3), PGA2 (300 ng/h; n = 4), or PGF2 alpha (10 ng/h; n = 8) was infused via osmotic minipump beginning at midluteal phase (Days 5-8 after the estimated LH surge) until menses. In addition, the same dose of PGE, PGD, PGI, or PGA was infused in combination with PGF2 alpha (n = 3-4/group) for 7 days. P levels over 5 days preceding treatment were not different among groups. In 5 of 8 monkeys receiving PGF2 alpha alone, P declined to less than 0.5 ng/ml within 72 h after initiation of infusion and was lower (p less than 0.05) than controls. The length of the luteal phase in PGF2 alpha-infused monkeys was shortened (12.3 +/- 0.9 days; mean +/- SEM, n = 8; p less than 0.05) compared to controls (15.8 +/- 0.5). Intraluteal infusion of PGE, PGD, PGI, or PGA alone did not affect patterns of circulating P or luteal phase length.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cell-type specific responses in prostaglandin secretion by glandular and stromal cells from pig endometrium treated with catecholestrogens, methoxyestrogens and progesterone.

The pig conceptus and endometrium possess the ability to convert estrogens into catecholestrogens and catecholestrogens into methoxyestrogens. Experiments were carried out to evaluate the effect of catecholestrogens, methoxyestrogens and progesterone on the secretion of prostaglandin (PG) E and F2 alpha by porcine endometrial glandular and stromal cells in vitro. Both 2-hydroxyestradiol (2-OH-E2, 0-20 microM) and 4-hydroxyestradiol (4-OH-E2, 0-20 microM) increased (P less than .05) PGE and PGF2 alpha secretion by stromal cells in a dose response manner. Two-hydroxyestradiol tended (P less than .1) to decrease PGF2 alpha production by glandular cells. Two-methoxyestradiol (20 microM) suppressed (P less than .05) PGF2 alpha secretion by glandular and stromal cells. Four-methoxyestradiol (20 microM) stimulated (P less than .05) PGE production and PGE:PGF2 alpha ratio. Progesterone (.1 microM) suppressed (P less than .05) PG secretion in both cell types. We conclude that catecholestrogens, methoxyestrogens, and progesterone may participate in the establishment of pregnancy by modulating PG production in the endometrium.     

High-affinity prostaglandin E receptors attenuate adenylyl cyclase activity in isolated bovine myometrial membrane

Purified bovine myometrial plasma membranes were used to characterize prostaglandin (PG) E2 binding. Two binding sites were found: a high-affinity site with a dissociation constant (KD) of 0.27 +/- 0.08 nM and maximum binding (Bmax) of 102.46 +/- 8.6 fmol/mg membrane protein, and a lower affinity site with a KD = 6.13 +/- 0.50 nM and Bmax = 467.93 +/- 51.63 fmol/mg membrane protein. Membrane characterization demonstrated that [3H]PGE2 binding was localized in the plasma membrane. In binding competition experiments, unlabelled PGE1 displaced [3H]PGE2 from its receptor at the same concentrations as did PGE2. Neither PGF2 alpha nor PGD2 effectively competed for [3H]PGE2 binding. Adenylyl cyclase activity was inhibited at concentrations of PGE2 that occupy the high-affinity receptor. These data demonstrate that two receptor sites, or states of binding within a single receptor, are present for PGE2 in purified myometrial membranes. PGE2 inhibition of adenylyl cyclase activity support the view that cAMP has a physiological role in the regulation of myometrial contractility by PGE2.     

Comparison of plasma prostanoid levels in the human cord artery in normal and fetal distressed deliveries

Prostaglandin E2 (PGE2), thromboxane B2 (TXB2; as a stable metabolite of TXA2), prostaglandin F2 alpha (PGF2 alpha) and 6-keto-PGF1 alpha (as a stable end product of prostacyclin) have been measured by using specific radioimmunoassay in the plasma of the cord artery immediately after delivery before the cord was clamped. Plasma prostanoid concentrations in normal deliveries (n = 8, as controls) were 24.8 +/- 2.6 (PGE2), 246.8 +/- 37.0 (TXB2), 122.2 +/- 13.3 (PGF2 alpha) and 82.1 +/- 7.7 (6-keto-PGF1 alpha) respectively (pg/ml, mean +/- s.e). On the other hand, in fetal distressed deliveries showing continuous bradycardia (n = 6), they increased significantly to 275.4 +/- 20.1 (PGE2), 948.6 +/- 102.5 (TXB2), 218.0 +/- 21.4 (PGF2 alpha) and 1498.6 +/- 298.4 (6-keto-PGF1 alpha) respectively (pg/ml, mean +/- s.e, p less than 0.005). However, both PGF2 alpha/PGE2 and TXB2/6-keto-PGF1 alpha ratios declined significantly from 4.70 +/- 0.33 to 0.68 +/- 0.05 and from 3.07 +/- 0.37 to 0.68 +/- 0.12 respectively (mean +/- s.e, p less than 0.005) in the fetal distressed group compared with those of the controls. From these results, it may be concluded that the cord artery, which is known as the patent source for the production of PGE2 and prostacyclin, did exert a sufficiently strong reaction to overcome the undesirable haemodynamic changes to maintain the fetal well-being in utero.     

Modulation of renal hemodynamics by renal eicosanoids during vasopressor infusions in man

Pressor doses of norepinephrine (NE) (n = 8) and angiotensin II (A II) (n = 5) were infused in normal volunteers to determine whether the systemic administration of vasopressor hormones influence renal eicosanoid production and whether, in turn, the eicosanoids produced could modulate renal hemodynamics and electrolyte excretion. At the doses administered, both pressor substances induced the expected rise in blood pressure, a significant decrease (P less than 0.05) in renal blood flow and a proportionally smaller fall in glomerular filtration rate, resulting in a consistent augmentation in filtration fraction. Fractional sodium excretion was concomitantly reduced. NE infusion produced only slight modifications in urinary prostaglandin (PG)E2, 2,3-dinor-6-keto-PGF1 alpha and thromboxane (TX)B2, while urinary 6-keto-PGF1 alpha and PGF2 alpha were increased by 38% and 176% respectively. The increase in urinary 6-keto-PGF1 alpha (the non-enzymatic degradation product of PGI2, predominantly of cortical origin) was proportional to the level of circulating NE (r = 0.78, P less than 0.05) and to the renal vascular resistance (r = 0.85, P less than 0.01), suggesting an immediate compensatory role for PGI2 in response to the NE-induced pressor stimulus. The renal production of PGE2 and PGF2 alpha (predominantly medullary) was inversely correlated with the filtration fraction: the greater the increase in PGE2 and PGF2 alpha the lower the elevation in filtration fraction or the decline in renal blood flow upon NE administration. All infusion variably stimulated the renal eicosanoid production: PGE2, 41%; PGF2 alpha, 102%; 6-keto-PGF1 alpha, 38%; 2,3-dinor-6-keto-PGF1 alpha, 38%; and TXB2, 25%.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of danazol, mefenamic acid, norethisterone and a progesterone-impregnated coil on endometrial prostaglandin concentrations in women with menorrhagia

The effects of four medical treatments have been assessed on menstrual blood loss (MBL) and endometrial prostaglandin (PG) concentrations in 30 women with objectively confirmed menorrhagia. Patients were randomly treated with danazol, 200 mg daily (n = 6), mefenamic acid, 500 mg three times daily during menses (n = 8), norethisterone, 5 mg twice daily from day 15-25 of the cycle (n = 8) or a progesterone-impregnated coil releasing 65 micrograms progesterone daily (n = 8). Endometrial biopsies were obtained in the mid-luteal phase before and after treatment in 23 cases, and assayed for PG content using radioimmunoassay. Treatment with norethisterone had no effect on either MBL or the concentration of PGs in the endometrium. MBL was significantly reduced after treatment with mefenamic acid (P = 0.05, n = 6) and the progesterone coil (P less than 0.05, n = 6), and was reduced in each of 4 cases treated with danazol in whom endometrial biopsies were available. Although there was no consistent change in endometrial PG concentrations in either the mefenamic acid or danazol groups, the lower MBL after insertion of the progesterone coil was associated with a reduced endometrial content of PGE, PGF2 alpha and "total" PG (6oxo PGF1 alpha + PGE + PGF2 alpha)-P = 0.05. Whereas the cyclooxygenase inhibitor mefenamic acid is likely to exert its effect on endometrial PGs at the time of menstruation itself, the continuous administration of progesterone throughout the menstrual cycle could result in both an impairment in estrogen receptor generation leading to reduced estrogen-mediated cyclooxygenase activity, and an increase in endometrial PG metabolism.     

In vivo levels of prostaglandin F2 alpha, E2 and prostacyclin in the corpus luteum of pregnant and pseudopregnant rats

Prostaglandin F2 alpha (PGF2 alpha) is a well-known luteolytic factor in the rat corpus luteum. To investigate a possible luteal origin of PGF2 alpha, measurements of this prostaglandin were performed in different luteal tissues in vivo. Prostaglandin E2 (PGE2) and the stable metabolite of prostacyclin, 6-keto-PGF1 alpha, were assayed simultaneously. Corpora lutea of different ages from 57 pregnant and pseudopregnant rats (mated with sterile males) were rapidly excised, dissected in 0 degree C indomethacin solution, homogenized, and extracted for prostaglandins with solid-phase extraction cartridges. Prostaglandins were determined by radioimmunoassay. Plasma levels of progesterone and 20 alpha-dihydroprogesterone were also monitored. In the adult pseudopregnant rat model, luteolysis occurs at Day 13 +/- 1, and maximal levels of all three prostaglandins were detected on Day 13 of pseudopregnancy: 0.40 +/- 0.02, 2.6 +/- 0.29, and 1.76 +/- 0.24 pmol/mg protein (mean +/- SEM, n=7) for PGF2 alpha, PGE2, and 6-keto-PGF1 alpha respectively. In pregnant rats, on the corresponding day, levels were considerably lower: 0.15 +/- 0.02, 0.90 +/- 0.13, and 0.50 +/- 0.06 pmol/mg protein (mean +/- SEM, n=9, p less than 0.0001), respectively. Luteal levels in pregnant rats showed a continuous decline on Days 13 and 19 for all prostaglandins measured, whereas in pseudopregnant rats an increment of PGF2 alpha was noted between Days 7 and 13 and remained high on Day 19. PGE2 closely followed levels of PGF2 alpha, but at a 5- to 10-fold higher level. The coefficient of correlation between PGF2 alpha and PGE2 in the luteal compartment of both models was 0.87 (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)