[3H]prostaglandin F2 alpha membrane binding reexamined

Uterine motility in the reptileAnolis carolinensis: interactive effects of tension, prostaglandins, calcium, and vasotocin

Uteri of Anolis carolinensis exhibited spontaneous rhythmic contractions in vitro. Addition of arginine vasotocin (AVT) caused an immediate, strong, tonic contraction followed by rhythmic contractions with the same frequency as spontaneous contractions but of a greater amplitude. At low tension (1.5 g) the AVT-induced tonic contraction was blocked by low dose of indomethacin, suggesting that it is influenced by calcium rather than prostaglandins (PGs). An increase in tension (from 1.5 to 15 g) reduced the duration of the AVT-induced tonic contraction; this stretch-induced decrease was also blocked by indomethacin. Stretch also decreased the duration of the rhythmic contractions, but this stretch effect was not inhibited by indomethacin. The rest interval between rhythmic contractions was decreased by PGF2alpha and PGE2, and indomethacin or stretch blocked these PG effects. Indomethacin, AVT, or stretch alone did not affect PGF2alpha secretion from AVT-treated uteri. Stretch also reduced PGF2alpha secretion from AVT-treated uteri, an effect inhibited by indomethacin.

Cloning of a buffalo (Bubalus bubalis) prostaglandin F2α receptor: changes in its expression and concentration in the buffalo cow corpus luteum

Acting primarily through its specific G protein-coupled receptor termed FPr, prostaglandin (PG) F2αinduces regression of the corpus luteum (CL) at the end of a non-fertile oestrous cycle. This study was aimed at cloning a full-length cDNA for FPr and determining its expression and protein concentrations during different stages of CL development in the water buffalo. Serum progesterone and StAR expression were determined to establish temporal relationships between indices of steroidogenesis and changes in FPr expression at different stages of CL development. In contrast to the dairy cow, the stage IV CL (day 20 of the oestrous cycle) did not appear to be functionally regressed in the buffalo. Molecular cloning of a cDNA encoding the buffalo FPr yielded a full length 2193 bp FPr cDNA containing a single open reading frame encoding a 362 amino acid protein with seven putative membrane-spanning domains. The deduced buffalo FPr amino acid sequence possesses a high degree of identity with the other mammalian homologues. Steady state concentration of buffalo FPr transcript increased (P> 0.05) from stage I to stage II/III, and declined at 18 h post PGF2αinjection. The FPr concentration expressed as fmol/μg of plasma membrane protein showed an increase (P> 0.05) from stage I (1.98 ± 0.10), through stage II/III (2.42 ± 0.48) to stage IV (2.77 ± 0.18). High affinity FPr was observed in stage I (Kd4.86 nmol) and stage II/III (Kd6.28 nmol) while low affinity FPr (Kd19.44 nmol) was observed in stage IV. In conclusion, we have cloned a full length FPr cDNA from buffalo cow CL and observed that FPr mRNA expression, receptor number and affinity did not vary significantly (P> 0.05) within the luteal phase of the oestrous cycle.

Changes in ovarian oxytocin secretion as an indicator of corpus luteum response to prostaglandin F2α treatment in cattle

Exogenous prostaglandin F(2alpha) (PGF(2alpha)) rapidly increases ovarian oxytocin (OT) release and decreases progesterone (P4) secretion in cattle. Hence, the measurement of OT secretion (the area under the curve and the height of the peak) after different doses of Oestrophan - PGF(2alpha) analogue (aPGF(2alpha)) on Days 12 and 18 of the estrous cycle (estrus = day 0), could be a suitable indicator of corpus luteum (CL) sensitivity to PGF(2alpha) treatment. Mature heifers (n = 36) were used in this study. Blood samples were collected from the jugular vein for the estimation of OT, P4 and 13, 14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM). In Experiment 1, different doses of aPGF(2alpha) (400, 300, 200 and 100 microg) given on Day 12 of the estrous cycle (n = 8) shortened (P < 0.05) the cycle duration (15.2 +/- 0.6 d) compared with that of the control (21.7 +/- 0.4 d). Successive heifers were also treated on Day 12 with 200 (n = 2), 100 (n = 2), 75 (n = 2) or 50 microg aPGF(2alpha) (n = 2). Only the 50 microg aPGF(2alpha) dose did not cause CL regression, although it increased OT concentrations to levels comparable to those observed during spontaneous luteolysis (50 to 70 pg/ml). In Experiment 2, on Day 18 of the cycle heifers (n = 8) were treated with 50, 40, 30 and 20 microg aPGF(2alpha). There was a dose-dependent effect of aPGF(2alpha) on OT secretion on Day 18 of the estrous cycle (r = 0.77; P < 0.05). In Experiment 3, an injection of 500 microg aPGF(2alpha) on Day 12 (n = 4) and 50 microg aPGF(2alpha) on Day 18 (n = 4) caused a similar (P > 0.05) increase in the OT concentration (288.5 +/- 23.0 and 261.5 +/- 34.7 pg/ml, respectively). Thus the effect of the same dose of aPGF(2alpha) (50 microg) on OT secretion was different on Days 12 and 18 of the cycle. To evoke similar OT secretion on Days 12 and 18 the dose of aPGF(2alpha) on Day 18 could be reduced 10-fold, confirming that CL sensitivity to PGF(2alpha) appears to increase in the late luteal phase.

Cloning, sequencing and proposed structure for a prostaglandin F2 alpha receptor regulatory protein

The cDNA has been cloned for a protein which copurifies with and colocalizes with [3H]PGF2 alpha binding activity, yet differs from the previously cloned prostaglandin F2 alpha receptor. Polyclonal antibody, produced against one of two protein bands present in a highly purified preparation of [3H]PGF2 alpha binding activity isolated from pregnant bovine corpus luteum, was used to screen a rat ovary cDNA expression library. A single strongly positive clone was identified containing a 4 kilobase (kb) insert. Northern analysis using this cDNA as a probe revealed the expression of a 6 kb mRNA with a tissue distribution similar to that seen by immunohistochemical analysis with the polyclonal antibody. Tissues possessing the largest quantity of the protein's mRNA are reproductive tissues, lung, and heart. Directed cDNA synthesis was required to clone the 5' end of the cDNA. Verification that the correct cDNA was cloned is provided by alignment of the predicted protein's mature amino terminal amino acid sequence with sequence observed by protein sequencing. Translation of the predicted 879 amino acid open reading frame (ORF) suggests a protein structure exhibiting six glycosylated immunoglobulin type loops, one of which may either be membrane associated or may be the site of association with another protein, a transmembrane region, and a short, highly charged, carboxy terminal cytoplasmic tail. Based upon searches of the NIH and EMBL protein databanks, this is a unique protein. The FPRP mRNA is notable for a highly structured G,C rich 5' end and over 3 kb of 3' untranslated region (UTR) that includes 7 ATTTA 'destabilization sequences' and an 'inflammatory mediator'-like sequence. These characteristic sequences in the 3' UTR suggest that the mRNA is tightly regulated and may code for a protein that is functionally related to an inflammatory mediator. Functional studies in the accompanying report suggest a negative regulatory function for this protein. We suggest the name prostaglandin F2 alpha receptor regulatory protein (FPRP).

Negative regulatory activity of a prostaglandin F2 alpha receptor associated protein (FPRP)

The cDNA has been cloned for a protein which copurifies with and colocalizes with [3H]PGF2 alpha binding activity. This cloning was based on prior purification of the [3H]PGF2 alpha binding complex from pregnant corpus luteum, antibody production against the protein of interest, and antibody screening of a rat ovary cDNA expression library. Here I report on the activity of this prostaglandin F2 alpha receptor (FP) associated protein (FPRP). Expression of the FPRP cDNA in COS cells results in production of a full length (approximately 130 kD) immunoreactive molecule with an endoplasmic reticulum and Golgi network distribution similar to that seen in granulosa lutein cells. COS cell expressed FPRP inhibits binding of [3H]PGF2 alpha to FP of COS cell origin or FP expressed from cotransfected rat or mouse FP cDNA in a dose-dependent manner. This inhibition of [3H]PGF2 alpha binding by FPRP occurs only when the FPRP cDNA is expressed in the same cell as the FP resides, reaches a maximum of approximately 80%, and is unaffected by second messenger perturbing agents such as phorbol ester, 8-Br-cAMP, calcium ionophore A23187, and okadaic acid. Scatchard analysis indicates that FPRP induces a decrease in receptor number rather than affinity constant, suggesting a non-competitive means of inhibition. Molecular dissection of the FPRP protein indicates that two portions of the molecule play a role in the inhibition of FP. Whether FPRP is an FP-associated regulatory molecule, an FP subunit, or a receptor for a PGF2 alpha-antagonistic ligand is presently unknown. Physiological relevance and significance of FPRP are discussed. During the course of these experiments it was necessary to clone the rat FP cDNA.

Olfaction and gustation in fish: an overview

Living in an aquatic environment, often devoid of light but rich in dissolved compounds, fish have highly developed chemosensory and chemical signalling systems. The olfactory and gustatory systems comprise the major chemosensory pathways. Despite considerable variations in structural organization of the peripheral olfactory organ throughout fish species, ultrastructural organization of the olfactory sensory epithelium is extremely consistent. The olfactory receptor cell is a bipolar neurone which is directly exposed to the external environment and sends information to the brain by its own axon (cranial nerve I). Four major classes of chemicals have been identified as specific olfactory stimuli and their stimulatory effectiveness characterized: amino acids, sex steroids, bile acids/salts and prostaglandins. Olfactory signals such as those involved in reproduction and feeding may be processed independently through two distinct subsystems: the lateral and medial olfactory systems. The taste buds constitute the structural basis of the gustatory organ. Taste buds may occur not only in the oropharyngeal cavity, but on the whole body surface. Chemical information detected by specialized epithelial cells, gustatory cells, is transmitted to the central nervous system by cranial nerve VII (facial), IX (glossopharyngeal), and X (vagal). Besides diverse sensitivities and specificities for amino acids, fish gustatory receptors detect various organic acids, nucleotides and bile salts. Putative receptors, molecular mechanisms of transduction and the role played by olfaction and gustation in feeding, reproduction, migration and other fish behaviours are discussed.

Studies on prostanoid receptors in ocular tissues

Cyclooxygenase products of arachidonic acid, for example prostaglandins (PGs), prostacyclin, and thromboxane A2, mediate a wide range of physiological actions. Vasodilation, increased vascular permeability, platelet aggregation and its inhibition, and immunomodulation are some of the important biological actions of cyclooxygenase products (1). Depending on type and dose, PGs cause vasodilation, increase or decrease intraocular pressure, and disrupt the blood-aqueous barrier (2, 3). These actions also vary qualitatively and quantitatively with the animal species. Prostaglandins, like any biological molecule, must act by binding with their specific receptors. Coleman and coworkers (4, 5), from a series of studies with PG agonists and antagonists in vascular and non-vascular smooth muscle preparations, classified PG receptors. This classification led to a greater appreciation of the relationship between PG actions and specific PG receptors in various tissues. Ocular actions of PGs linked with specific PG receptors are far from being clear. In this communication we will review our work on PG binding sites in ocular tissues and PG receptors coupled to adenylyl cyclase or phosphoinositidase C signal transduction pathways in ocular tissues of various animal species.

Immunohistochemical localization of PGF2 alpha receptor in the rat oviduct

As a step towards understanding the role of prostaglandin F2 alpha (PGF2 alpha) in female reproductive tract physiology, a rabbit polyclonal antiserum reactive with purified PGF2 alpha receptor (PGF2 alpha-R) was produced. Here we describe use of this anti-PGF2 alpha-R antiserum in immunohistochemical staining of rat oviduct to ascertain which cell types, in vivo, possess immunoreactive PGF2 alpha-R. Western blot analysis was initially performed and confirmed that the anti-PGF2 alpha-R antiserum recognizes only one oviductal antigen. The immunopositive antigen is similar in molecular mass (by PAGE) to the previously described, purified PGF2 alpha-R molecule. Immunohistochemical staining demonstrates that adult rat oviduct contains a single subpopulation of cells with PGF2 alpha-R, and that subpopulation is a ciliated epithelial cell type found predominantly in the isthmus and distal ampullae near the isthmus-ampullae junction (I-AJ). None of these PGF2 alpha-R immunopositive cells are found in the epithelium of infundibulum oviduct. PGF2 alpha-R containing cells are not randomly distributed in the epithelium on cross-section of the isthmus and ampullae oviduct, rather, they are almost always in the crypts between infoldings of the mucosa. The relative number of this I-AJ PGF2 alpha-R containing epithelial cell subpopulation appears to vary with the phase of the rat's estrus cycle. Diestrus I-AJ epithelium contains one-half to one-third as many PGF2 alpha-R containing cells as it does in proestrus, estrus or metestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of PGF2 alpha receptor in the rat ovary

As a step towards understanding the role of prostaglandin F2 alpha (PGF2 alpha) in ovarian function, a rabbit antiserum against purified PGF2 alpha receptor (PGF2 alpha-R) was produced. This report details the use of this antiserum in immunohistochemical staining of ovaries of non-pregnant and pregnant rats to ascertain which cell types, in vivo, possess PGF2 alpha-R. In non-pregnant rats, three ovarian cell subpopulations contain immunoreactive PGF2 alpha-R. These include: a subpopulation of the cells found in corpora lutea, a subpopulation of the thecal cells surrounding secondary and mature (Graafian) follicles, and a subpopulation of primary and secondary interstitial cells. The ovarian tissues and cell types in which immunoreactive PGF2 alpha-R cannot be demonstrated include: the serosa overlying the ovary and its vessels, the coelomic epithelium and its underlying cortical stroma, medullary stroma and vessels, granulosa cells of primary, secondary and mature follicles, the oocyte, and the blood vessels and stroma within corpora lutea. PGF2 alpha-R immunohistochemical staining of corpora lutea from non-pregnant animals was examined both prior to the start of luteolysis and during luteolysis. During luteolysis, cells undergoing apoptosis stained for the presence of PGF2 alpha-R. PGF2 alpha-R immunohistochemical staining was also examined in corpora lutea during pregnancy and until 4 days postpartum. The major findings here were the apparent large increase in staining intensity of granulosa-lutein cells during pregnancy, and the loss of PGF2 alpha-R immunopositivity of the granulosa-lutein cells during the postpartum period. In summary, three ovarian cell subpopulations, all of which can secrete steroids, possess immunoreactive PGF2 alpha-R.

Identification and purification of a bovine corpora luteal membrane glycoprotein with [3H]prostaglandin F2-alpha binding properties

A bovine corpora luteal membrane glycoprotein which coelutes from multiple chromatographic procedures with bound tritiated prostaglandin F2a ([3H]PGF2 alpha) has been identified and purified to homogeneity. The properties of this molecule include: an apparent molecular mass by polyacrylamide gel electrophoresis (PAGE) of 135 kD; glycosylation which resists endoglycosidases D and H but is susceptible to cleavage by the exoglycosidase sialidase; binding of the molecule to Wheat Germ Agglutinin Sepharose but not to Concanavalin A Sepharose or Soybean Agglutinin Sepharose; migration on O'Farrell 2-D PAGE (pI 3-10) to the acidic side of the gel; binding to DEAE-Cellulose at pH 7.5 which can be displaced with NaCl at concentrations above approximately 100 mM; and, when solubilized with Triton X-100, binding to Phenyl-Sepharose or Octyl-Sepharose columns. Lastly, a rabbit polyclonal antibody against this [3H]PGF2 alpha binding protein has been made which allows both Western blotting of the 135 kD protein as well as immunohistochemical staining of ovarian tissue in a manner expected from previous binding studies. Problems associated with membrane solubilization of the receptor and receptor renaturation are discussed.