Depot-dependent effects of adipose tissue explants on co-cultured hepatocytes

We have developed an in vitro hepatocyte-adipose tissue explant (ATE) co-culture model enabling examination of the effect of visceral and subcutaneous adipose tissues on primary rat hepatocytes. Initial analyses of inflammatory marker genes were performed in fractionated epididymal or inguinal adipose tissues. Expressions of inflammation related genes (IL-6, TNF-α, COX-2) were higher in the inguinal than the epididymal ATE. Similarly, expressions of marker genes of macrophage and monocyte (MPEG-1, CD68, F4/80, CD64) were higher in the stromal vascular fraction (SVF) isolated from inguinal ATE than that from epididymal ATE. However, expressions of lipolysis related genes (ATGL, HSL, perilipin-1) were higher in the epididymal adipocytes than inguinal adipocytes. Moreover, secretion of IL-6 and PGE(2) was higher from inguinal ATEs than from epididymal ATEs. There was a trend that the total levels of IL-6, TNF-α and PGE(2) in the media from inguinal ATEs co-cultured with primary rat hepatocytes were higher than that in the media from epididymal ATEs co-cultured with hepatocytes, although the significant difference was only seen in PGE(2). Lipolysis, measured as glycerol release, was similar in the ATEs isolated from inguinal and epididymal adipose tissues when cultured alone, but the glycerol release was higher in the ATEs isolated from epididymal than from inguinal adipose tissue when co-cultured with hepatocytes. Compared to epididymal ATEs, the ATEs from inguinal adipose tissue elicited a stronger cytotoxic response and higher level of insulin resistance in the co-cultured hepatocytes. In conclusion, our results reveal depot-dependent effects of ATEs on co-cultured primary hepatocytes, which in part may be related to a more pronounced infiltration of stromal vascular cells (SVCs), particularly macrophages, in inguinal adipose tissue resulting in stronger responses in terms of hepatotoxicity and insulin-resistance.     

Regulation of leptin release and lipolysis by PGE2 in rat adipose tissue

The role of eicosanoids formed by adipose tissue from rats was examined in the presence of the specific cyclooxygenase-2 inhibitor NS-398. This agent totally blocked the release of prostaglandin E2 (PGE2) by rat adipose tissue over a 24-h incubation in primary culture. The final concentration of PGE2 after 24 h was 12 nM, and half-maximal inhibition of PGE2 formation required 35 nM NS-398. While inhibition of PGE2 formation by NS-398 had no effect on basal leptin release or lipolysis, it enhanced the lipolytic action of 10 nM isoproterenol by 36%. The in vivo administration of PGE2 doubled serum leptin. PGE2 also directly stimulated leptin release by rat adipose tissue incubated in the presence of 25 nM dexamethasone, which inhibited endogenous PGE2 formation by 94%. The inhibition of lipolysis as well as the stimulation of leptin release by PGE2 were mimicked by N6-cyclopentyladenosine (CPA). These data indicate that exogenous PGE2 can stimulate leptin release by adipose tissue when the basal formation of PGE2 is blocked by dexamethasone. However, while the endogenous formation of PGE2 does not appear to regulate basal lipolysis or leptin release, it may play a role in the activation of lipolysis by catecholamines.     

Eicosanoids as endogenous regulators of leptin release and lipolysis by mouse adipose tissue in primary culture

Prostaglandin E(2) (PGE(2)) stimulated leptin release over a 24-h incubation of mouse adipose tissue in primary culture. The maximal stimulation of leptin release was seen with 100 nm PGE(2). The role of endogenous eicosanoids in the regulation of lipolysis and leptin formation was examined in the presence of NS-398, a selective cyclooxygenase-2 inhibitor. NS-398 at a concentration of 5 microm enhanced lipolysis by 30% and lowered leptin release by 24%. This concentration of NS-398 almost completely inhibited PGE(2) formation. An inhibition of basal lipolysis by PGE(2) or N(6)-cyclopentyladenosine (CPA) was seen in the presence but not in the absence of NS-398. CPA, whose receptor, like that of PGE(2) inhibits cyclic AMP accumulation in adipose tissue, also enhanced leptin release. These data indicate that PGE2 can stimulate leptin release and suggest that endogenous eicosanoids affect both lipolysis and leptin formation by mouse adipose tissue.     

Oxytocin enhances the basal release of uterine prostaglandin F2 alpha, but not that of PGE1, or of PGE2, and changes the metabolism of exogenous arachidonate, favouring the formation of prostaglandin F2 alpha and 5-HETE. Relationships with its uterotonic action and modulation by estradiol

We attempted to explore possible mechanism(s) subserving the influence of oxytocin on uterine motility by studying the action of the hormone on: 1) the contractile activity of isolated rat uteri in the presence or absence of indomethacin; 2) the synthesis and release of prostaglandins (PGs) into the solution incubating the uterine tissue as well as the metabolism of labelled arachidonic acid; 3) the uptake of 45Ca2+ by uterine strips. The experiments were bone with uterine preparations isolated from spayed rats treated or not with 17-beta-estradiol. The values of isometric developed tension (IDT) and of frequency of contractions (FC) induced by oxytocin in uterine strips isolated from spayed and spayed-estrogenized rats, were not modified by indomethacin at 10(-6) M. On the other hand, uterine strips from untreated spayed rats, release into the incubating medium approximately equal amounts of PGE1, PGE2 and PGF2 alpha. The in vitro presence of oxytocin (50 mU/ml) increased significantly (p 0.05) the output of PGF 2 alpha without changing the release of PGE1 or PGE2. Uteri from spayed rats injected prior to sacrifice with 17-beta-estradiol released significantly less PGE1 and PGE2 (p less than 0.005) than preparations from non-injected animals, whereas the output of PGF2 alpha in the suspending solution remained unchanged. Following estrogenization the addition of oxytocin to preparations obtained from spayed-estrogenized rats also increased the output of uterine PGF2 alpha (p less than 0.001) without changing that of PGs E1 or E2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influences of estradiol and of catechol and non-catechol estrogens on the output of prostaglandins in uteri from spayed rats

The effects of 17-beta estradiol and of some catechol and non-catechol-estrogens on the synthesis and output of prostaglandins (PGs) E and F by uteri from ovariectomized rats, were explored. Uteri from castrated animals released twice as much PGE than PGF. When uterine tissue was obtained from spayed rats injected prior to sacrifice with a low dose of 17-beta estradiol (0.5 + 1.0 microgram, on two consecutive days), the output of PGE diminished significantly. With a higher dose of the hormone (0.5 + 50.0 micrograms) the depressive influence on the synthesis and release of PGE was even more marked, whereas the output of PGF rose significantly. Low or high doses of estrone or of estriol failed to affect the release of either one of the PGs determined. On the other hand, 2-0H-estradiol at a low dose had no action but at a higher one inhibited the release of PGE without influencing PGF. Neither low nor high doses of 2-0H estriol or of 2-0H estrone affected the synthesis and release of uterine PGs. It was also observed that all the compounds tested evoked a significant uterotrophic action. It appears plausible that some catechol metabolites of 17-beta estradiol, but not other catechol-estrogens, could be involved in the mechanism of action of 17-beta estradiol modulating the production of PGs by the rat uterus.     

Differential effects of prostaglandin F2 alpha and of prostaglandins E1 and E2 on cyclic 3',5'-monophosphate production and intracellular calcium mobilization in avian uterine smooth muscle cells

The effects of prostaglandins (PGs) E1 (PGE1), E2 (PGE2) and F2 alpha (PGF2 alpha) on cyclic 3',5'-adenosine monophosphate (cAMP) production and intracellular Ca mobilization were examined in smooth muscle cells of chicken uterus grown in primary culture. At subnanomolar concentrations, both PGE1 and PGE2 significantly suppressed cAMP levels. However, at higher concentrations (0.1-100 microM), both agonists caused a dose-related increase in cAMP production. PGF2 alpha, on the other hand, had no effect on cAMP production. Forskolin (1-100 microM), which also stimulated cAMP production in a dose-dependent fashion, potentiated the effects of both PGE1 and PGE2. In digitonin-permeabilized uterine cells preloaded with 45Ca2+, the addition of PGF2 alpha caused a biphasic 45Ca2+ efflux. There was a small but significant 45Ca2+ release (10.0 +/- 1.5%) within 30 s (rapid phase), followed by a larger one (32.0 +/- 2.0%) within 5 min (slow phase). PGE2, at doses above 1 nM (which significantly increased cAMP accumulation), promoted 45Ca2+ sequestration. This action of PGE2 was observed as early as 1 min and was complete by 5 min. In addition, 0.001 nM PGE2 (a dose that was ineffective on 45Ca2+ mobilization) enhanced PGF2 alpha-induced 45Ca2+ mobilization from 22.5 +/- 5% to 57.0 +/- 3.5%. These results show that PGs of the E series have distinctly different effects on cAMP production and intracellular Ca mobilization. PGF2 alpha action may be linked directly to intracellular Ca mobilization, whereas the effects of PGE may be exerted at multiple sites depending on its local concentration. At low concentrations, its action may be mediated by the suppression of cAMP levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alterations in uterine and placental prostaglandin F and E with gestational age in the rat

Experiments were designed to determine the chronological alterations in placental and uterine prostaglandin F and E (PGF and PGE) during pregnancy in the rat. Pregnant rats (sperm in the vagina = day 0) were sacrified at days 15, 18,19, 20, 21 and delivery (day 21 ) and placental and uterine tissues assayed (RIA) for PGF and PGE immediately (“ ”) or after 1 hour incubation (“ ”). Uterine content of PGF and PGE (ng PG/mg DNA) was increased significantly by day 19 and further increases were seen through delivery. Incubation of uterine tissue resulted in enhanced net production of PGF and PGE (p <.05) per mg DNA (as judged by tissue content and release into the incubation medium) by day 18 of pregnancy vs. day 15. Net production peaked around the time of delivery thus paralleling the alterations in tissue content .By contrast, no differences with gestational age were found in placental content of PGF and PGE , the concentrations throughout late gestation remaining in the range of uterine PGs at day 15. However, production of PGs per mg placental DNA increased markedly during incubation with significant enhancement detected by day 19 vs. 15, achieving levels even greater than the uterus .The and findings for the uterus are consistent with the hypothesis that increases in uterine PGs levels at the end of pregnancy may play an important role in parturition. The experiences with placental tissue suggest that the potential for PG production per placental cell may also increase in late gestation and thereby contribute to the augmented intrauterine availability of PGs at that time.     

Prostaglandin release by zygotes and endometria of pregnant rabbits

When 4-day rabbit zygotes were incubated for 1 h at 37 degrees C in vitro, very little prostaglandin (PG) was released into the medium, and the concentration of PGs in the zygotes after incubation was also low. The release of prostaglandin E (PGE) and prostaglandin F (PGF) into the medium, and their concentration in the zygotes after incubation, increased sharply on Days 6 and 7 of pregnancy, reaching, by Day 7, values close to 200 ng of each PG released in 1 h per mg of protein. By contrast, endometrial samples on Days 4 and 5 of pregnancy released more PGF and less PGE than the zygotes of the same ages on a per mg of protein basis, and on Days 6 and 7, less of both PGs. Furthermore, endometrial concentrations of PGs after incubation, except for PGF on Day 4, were always lower than values for zygotes. Endometrial concentrations of PGs on Day 6 were lower before than after incubation. Although there was a slight upward trend in PG release by endometrial samples with increasing length of pregnancy, the changes were minimal and, in the case of PGE, none of the mean values exceeded 1 ng per mg of protein. In 7-day blastocysts, high levels of both PGF and PGE were found in the blastocoelic fluid, and these did not change during the 1-h incubation. The release of PGF and PGE during in vitro incubation of ruptured and washed Day 6 blastocysts was stimulated by arachidonic acid, and that of PGF, but not PGE, inhibited by indomethacin. The release of PGE, but not of PGF, from Day 6 blastocysts was inhibited by low temperature, and the same conditions inhibited release of both PGF and PGE from endometrial cell suspensions. It seems that both blastocysts and endometria have capability to synthesize PGs, the blastocysts being particularly active in this regard on Days 6 and 7 of pregnancy. It is hypothesized that, in vivo, Day 6 and 7 blastocysts release large quantities of PGs which trigger some of the local endometrial changes associated with pregnancy.     

The release of PGF2 alpha and PGE2 from separated cells of human endometrium and decidua

The capacity of separated glandular and stromal cells from endometrium and first trimester decidua to release prostaglandins (PGs) was studied over 48 hours in culture. Glandular preparations released more PGs than stromal preparations in all tissues. Stromal release of PGs did not alter throughout the cycle or in early pregnancy but the capacity of glandular preparations to release PGs varied considerably. Proliferative glands released most PGF2 alpha and PGE2 followed by secretory glands and decidua. Histamine (10(-5)) stimulated PG release from endometrial and decidual glands but the response of proliferative glands was greatest. Actinomycin D stimulated release of PGF2 alpha and PGE2 from glandular cells of secretory endometrium and decidua. These results suggest that in vitro release of PGs is suppressed after ovulation and is in part due to inhibition of PG release by a protein or proteins synthesized in the glandular fraction of secretory endometrium or decidua.     

Prostaglandins enhance parathyroid hormone-evoked increase in free cytosolic calcium concentration in osteoblast-like cells.

Prostaglandins (PGs) are autocrine or paracrine hormones that may interact with circulating hormones such as parathyroid hormone (PTH) in bone. We examined the interaction of the PGs, PGF2 alpha, PGE2, and 6-keto-PGF1 alpha with PTH to enhance the rapid, initial transient rise in free cytosolic calcium ([Ca2+]i) and cAMP levels stimulated by PTH. Pretreatment of UMR-106, MC3T3-E1, and neonatal rat calvarial osteoblast-like cells by PGs resulted in an enhancement of the early transient rise in [Ca2+]i stimulated by PTH. PGF2 alpha was approximately 100 times more potent than PGE2. PGE2 itself was more potent than 6-keto-PGF1 alpha in enhancing PTH-stimulated rise in [Ca2+]i. Near-maximal augmentation was achieved at PGF2 alpha doses of 10 nM and PGE2 of 1 microM. The degree of augmentation in [Ca2+]i by PGF2 alpha was independent of preincubation time. PGF2 alpha pretreatment did not alter the EC50 for the PTH-induced [Ca2+]i increase but only the extent of rise in [Ca2+]i at each dose of PTH. The augmented increase in [Ca2+]i was mostly due to enhanced PTH-mediated release of Ca2+ from intracellular stores. PGF2 alpha did not stimulate an increase in PTH receptor number as assessed by [125I]-PTH-related peptide binding. PG pretreatment partially reversed PTH inhibition of cell proliferation, suggesting that an increase in [Ca2+]i may play a role in tempering the anti-proliferative effect of PTH mediated by cAMP. These studies suggest a new mode by which PGs can affect cellular activity.     

Interactive roles of progesterone, prostaglandins, and collagenase in the ovulatory mechanism of the ewe

Interrelationships between production of progesterone (P4), prostaglandin (PG) E2 and PGF2 alpha, and collagenase by periovulatory ovine follicles and their possible involvements in the ovulatory process were investigated. Follicles were isolated from ovaries at intervals (0 to 24 h) after the initiation of the preovulatory surge of luteinizing hormone (LH). Progesterone and PGs within follicles were determined by radioimmunoassay. Digestion of radioactive collagen during coincubation with tissue homogenates was used to assess the production of a bioactive follicular collagenase(s). Follicular accumulation of PGs and P4 increased at 12 and 16 h, respectively, after the onset of the surge of LH; PGE2 then decreased at 20 h. Collagenolytic activity of follicular tissue increased at 20 h and was maximal at 24 h (during the time of follicular rupture). An inhibitor of synthesis of P4 (isoxazol) or PGs (indomethacin) was injected into the follicular antrum at 8 h. Isoxazol did not prevent the initial rise in PGs, but inhibited synthesis of PGF2 alpha at 16 h and therafter. Isoxazol negated the decline in PGE2 and increase in collagenolysis. Indomethacin did not influence synthesis of P4; however, it suppressed collagenolytic activity of follicular tissue. Ovaries with treated follicles were left in situ and observed for an ovulation point at 30 h. Isoxazol or indomethacin was a potent inhibitor of ovulation. The blockade of ovulation by isoxazol was reversed by systemic administration of P4 or PGF2 alpha, but not by PGE2. Reversal of the blockade by indomethacin was accomplished with PGE2 or PGF2 alpha. Collagenolytic activity of follicular tissue was likewise restored by such treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronic ethanol and triglyceride turnover in white adipose tissue in rats: inhibition of the anti-lipolytic action of insulin after chronic ethanol contributes to increased triglyceride degradation

Chronic ethanol consumption disrupts whole-body lipid metabolism. Here we tested the hypothesis that regulation of triglyceride homeostasis in adipose tissue is vulnerable to long-term ethanol exposure. After chronic ethanol feeding, total body fat content as well as the quantity of epididymal adipose tissue of male Wistar rats was decreased compared with pair-fed controls. Integrated rates of in vivo triglyceride turnover in epididymal adipose tissue were measured using (2)H(2)O as a tracer. Triglyceride turnover in adipose tissue was increased due to a 2.3-fold increase in triglyceride degradation in ethanol-fed rats compared with pair-fed controls with no effect of ethanol on triglyceride synthesis. Because increased lipolysis accompanied by the release of free fatty acids into the circulation is associated with insulin resistance and liver injury, we focused on determining the mechanisms for increased lipolysis in adipose tissue after chronic ethanol feeding. Chronic ethanol feeding suppressed beta-adrenergic receptor-stimulated lipolysis in both in vivo and ex vivo assays; thus, enhanced triglyceride degradation during ethanol feeding was not due to increased beta-adrenergic-mediated lipolysis. Instead, chronic ethanol feeding markedly impaired insulin-mediated suppression of lipolysis in conscious rats during a hyperinsulinemic-euglycemic clamp as well as in adipocytes isolated from epididymal and subcutaneous adipose tissue. These data demonstrate for the first time that chronic ethanol feeding increased the rate of triglyceride degradation in adipose tissue. Furthermore, this enhanced rate of lipolysis was due to a suppression of the anti-lipolytic effects of insulin in adipocytes after chronic ethanol feeding.     

Electric field stimulation alters the outputs of prostaglandins from isolated rat urinary bladder preparations. Influences of papaverine and tetradotoxin

The effects of electric field stimulation (EFS) on the outputs of prostaglandins (PGs) E1, E2 and F2 alpha from isolated contracting rat urinary bladders, were explored. Also, the influences of papaverine (5.10(-6) M) and of tetradotoxin (TTX = 5.10(-7) M) on PGs released by spontaneously contracting or electrically driven preparations, were tested. The basal control outputs of the three PGs in spontaneously contracting urinary bladders, had a comparable magnitude. On the contrary, in electrically stimulated preparations the output of PGE2 rose significantly; that of PGF2 alpha presented a significant reduction and the release of PGE1 was similar to that in controls. Papaverine failed to modify the profile of basal control PG release in non-stimulated bladders, abolished contractile responses to EFS and blocked the augmented output of PGE2 elicited by EFS. The presence of TTX in the suspending solution had no action on the basal control release of PGs from non-stimulated spontaneously contracting preparations, depressed between 80-90% the inotropic responses triggered by EFS and completely antagonized the enhanced output of PGE2 evoked by EFS. Results are discussed in terms of the relative participations of the evoked inotropism of the detrusor muscle or by the stimulation of nerve endings, accounting for the greater release of tissue PGE2 after EFS.     

Radioimmunoassay measurement of ACTH-facilitated PGE2 and PGF2alpha release from isolated cat adrenocortical cells.

Prostaglandin (PG) biosynthesis by trypsin-dispersed cat adrenocortical cells was studied by radioimmunoassay (RIA). Parallel assays of incubation media using PGF2alpha and PGF1alpha antisera established that PGF2alpha is the primary PGF released by feline cortical cells. Following the reduction of PGE to PGF with sodium borohydride (NaBH4) these same two antisera were also used to identify PGE2 as the primary PGE released. RIA using a PGE antiserum confirmed the presence of PGE in the incubation medium. Steroidogenic concentrations of ACTH (50-250muU) enhanced PGE and PGF release, and indomethacin suppressed the ACTH-facilitated release. These studies provide additional evidence for ACTH-induced PG synthesis by feline cortical cells, and support the hypothesis that PGs play some role in the steroidogenic action of ACTH.     

Gene deletion reveals roles for annexin A1 in the regulation of lipolysis and IL-6 release in epididymal adipose tissue

In this study, epididymal adipose tissue from male annexin 1 (ANXA1)-null and wild-type control mice were used to explore the potential role of ANXA1 in adipocyte biology. ANXA1 was detected by Western blot analysis in wild-type tissue and localized predominantly to the stromal-vascular compartment. Epididymal fat pad mass was reduced by ANXA1 gene deletion, but adipocyte size was unchanged, suggesting that ANXA1 is required for the maintenance of adipocyte and/or preadipocyte cell number. Epididymal tissue from wild-type mice responded in vitro to noradrenaline and isoprenaline with increased glycerol release, reduced IL-6 release, and increased cAMP accumulation. Qualitatively similar but significantly attenuated responses to the catecholamines were observed in tissue from ANXA1-null mice, an effect that was not associated with changes in beta-adrenoceptor mRNA expression. Lipopolysaccharide (LPS) also stimulated lipolysis in vitro, but its effects were muted by ANXA1 gene deletion. By contrast, LPS failed to influence IL-6 release from wild-type tissue but stimulated the release of the cytokine from tissue from ANXA1-null mice. ANXA1 gene deletion did not affect glucocorticoid receptor expression or the ability of dexamethasone to suppress catecholamine-induced lipolysis. It did, however, augment IL-6 expression and modify the inhibitory effects of glucocorticoids on IL-6 release. Collectively, these studies suggest that ANXA1 supports aspects of adipose tissue mass and alters the sensitivity of epididymal adipose tissue to catecholamines, glucocorticoids, and LPS, thereby modulating lipolysis and IL-6 release.     

Effects of the fetal-placental unit on uterine prostaglandin levels at term in the pregnant rat

Uterine prostaglandins (PGs) increase markedly at term in the pregnant rat. To assess the contribution of the fetal-placental unit (FPU) on uterine tissue and uterine venous blood PG concentrations, each uterine horn of 14 unilaterally pregnant rats at day 21 of pregnancy were compared. In addition, 7 bilaterally pregnant rats were studied. Uterine tissue and uterine venous plasma PGF, PGE, 6-Keto-PGF1 (6KF) and thromboxane B2 (TxB2) and systemic plasma progesterone, estradiol and estrone were determined by radioimmunoassay. Uterine concentrations of PGs (ng/mg DNA) were always greater on the pregnant side of unilaterally pregnant rats (p less than .05) although the PGF levels were elevated to a lesser extent than were PGE, TxB2 or 6KF. However, no differences were detected between uterine tissue from the pregnant side of unilaterally pregnant compared to bilaterally pregnant rats. In addition, no differences were found in uterine venous plasma PGs adjacent or opposite the pregnant uterine horn and in systemic plasma progesterone, estradiol and estrone levels in unilaterally vs bilaterally pregnant rats. These data suggest that the presence of the FPU is associated with an increased capacity of uterine tissue to produce PGE, TxB2 and 6KF, and to a lesser degree PGF, and thus may contribute to the increase in uterine PGs periparturition.     

A simple prostaglandin bioassay based on smooth muscle preparations from the human oviduct

A simple bioassay for the detection of PGE2, PGF2 alpha and PGI2 was developed by the use of smooth muscle preparations from the human oviduct. The circular muscle layer showed opposite responses to PGE2 and PGF2 alpha while the tubal artery was expedient to distinguish PGE2 from PGI2. As compared to earlier described PG bioassays the system showed a high sensitivity and the limit for detection of an unknown sample was approx. 1 ng. Also combinations of PGs could be identified when reference samples were administered parallel to the unknown samples. It is suggested that the described PG bioassay when further developed may be advantageous for certain purposes since the tissue material generally can be obtained at routine gynecological operations, thus avoiding the use of laboratory animals.     

Arachidonic acid metabolites in a nephroblastoma associated with paraneoplastic hypercalcemia

Blood concentration of PGE2, F2a, 6 keto PGF1a (6kF1a), TxB2 and 13, 14 dehydro 15 keto PGE2 (13, 14 OH 15 k E2) were measured in renal artery and vein of a patient with a PGs producing nephroblastoma. The tumor tissue produced PGs in the following order: PGF2a greater than PGE2 greater than TxB2 greater than 6kF1a greater than 13, 14 OH 15 k E2. However, renal artery concentration of the substances were as follows: 13, 14 OH 15 k E2 greater than TxB2 greater than 6kF1a greater than PGF2a greater than PGE2. Since arterial concentration is critical to postulating a calcium mobilizing effect on bone tissue, PGE2 arterial level seems to be too low to exert a pathogenetic role on hypercalcemia, at least in the patient reported here.     

Histamine alters prostaglandin output from diestrous rat uteri. Involvement of H2-receptors and 9-keto-reductase

The effects of exogenous histamine (H) on prostaglandin (PG) generation and release in uteri isolated from diestrous rats and the influences of H2-receptors blockers (cimetidine and metiamide) on the output of uterine PGs, were explored. Moreover, the action of H on the uterine 9-keto-reductase, was also studied. Histamine (10(-4) M) failed to alter the basal output of PGE1 but reduced significantly the generation and release of PGE2 and augmented the output of PGF2 alpha. On the other hand, cimetidine (10(-5) M) enhanced the basal release of PGE2 but had no action on the outputs of PGs E1 or F2 alpha. The enhancing effect of H on the production and release of PGF2 alpha was abolished in the presence of cimetidine. Also, the antagonist reversed the influence of H on the output of PGE2. Metiamide, another H2-receptor antagonist, did not alter the basal control generation and release of uterine PGs, but antagonized the augmenting influence of H on PGF2 alpha uterine output, as much as cimetidine did, and prevented the depressive action of H on the release of PGE2 from uteri. Histamine (10(-4) M) significantly stimulated uterine formation of cyclic-adenosine monophosphate, an action which was antagonized by the presence of cimetidine (10(-5) M), a blocker of H2 receptors. Also, histamine (10(-5) M) and dibutyrylcyclic-adenosine monophosphate (DB-cAMP) at 10(-3) M, enhanced significantly the formation 3H-PGF2 alpha from 3H-PGE2. Results presented herein demonstrate that H is able to diminish the generation of PGE2 in uteri from rats at diestrus augmenting the synthesis of PGF2 alpha, apparently via the activation of H2-receptors, enhancing adenylate-cyclase. These effects appear to increase uterine 9-keto-reductase activity which transforms PGE2 into PGF2 alpha. Relationships between the foregoing results and those evoked by estradiol, are also discussed.     

On the role of 'in vivo' injected progesterone and of the 'in vitro' presence of oxytocin, modulating Ca2+ uptake by the rat uteri from spayed animals and as controllers of the production of arachidonic acid metabolism.

We attempted to explore possible mechanism(s) subserving the influence of oxytocin (O) and of progesterone (P) in the isolated rat uterus studying the action of these hormones on: the synthesis and release of prostaglandins (PGs), the metabolism of labelled arachidonic acid and the uptake of Ca2+ by the tissue from ovariectomized animals. The experiments were done with uterine preparations isolated from spayed rats treated or not with P prior to sacrifice and afterward incubated or not with O 'in vitro'. While uterine strips from untreated spayed rat uterus exhibited a basal release into the incubating medium of approximately the same amounts of PGF2 alpha, and PGE2, the 'in vitro' addition of O (50 mU/ml) increased significantly (p < 0.05) the output of PGF2 alpha without changing the release of PGE2. In tissue from rats injected with P prior to sacrifice the output of PGF2 alpha rose significantly (p < 0.01) as it did after the addition of O to preparations obtained from spayed rats treated with P in comparison to findings in uteri from spayed rats but not in comparison to uteri from spayed rats treated with P alone. Moreover, the 'in vitro' addition of O (50 mU/ml) only increased the formation of PGF2 alpha (p < 0.05) and of 5-HETE (p < 0.05); nevertheless the administration of P to spayed rats diminished significantly (p < 0.05) the formation of 6-keto-PGF1 alpha from uteri, but increased that of PGF2 alpha (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)