Gonadotropin and prostaglandins binding sites in nuclei of bovine corpora lutea

Isolation and characterization of subcellular protein fractions from mouse heart

In this study, we report different protocols used to obtain highly enriched and well-characterized protein fractions that could be used to determine the subcellular localization of proteins. Different protein fractions (total, cytosolic, total membrane, sarcolemmal, and nuclear) were isolated from mouse heart by a combination of either polytron homogenization or liquid nitrogen pulverization followed by density gradient centrifugation. Triton X-100 was used in specific fractions to help in the solubilization of proteins obtained with fractionation protocols. Following the isolation, enzymatic assays and Western blot analysis were used to evaluate the enrichment and/or cross-contamination of these protein fractions. Glucose-6-phosphate dehydrogenase, Na+/K+-ATPase, mitochondrial Ca2+-ATPase, sarco-endoplasmic reticulum Ca2+-ATPase, glucose-regulated protein, and nucleoporin P62 were used as specific markers for the cytosol, sarcolemma, mitochondria, sarco-endoplasmic reticulum, endoplasmic reticulum, and nucleus, respectively. The results show that we obtained enriched protein fractions with little to no cross-contamination. These purification protocols allow us to obtain different protein fractions that could be used in a wide variety of studies.

Human chorionic gonadotropin/luteinizing hormone receptor expression in the adult rat spinal cord

The adult and fetal rat brain contains human chorionic gonadotropin/luteinizing hormone (hCG/LH) receptors, that are functional in mediating the neurotropic, neuroendocrine and behavioral actions of gonadotropins. We hypothesized that the spinal cord also contains these receptors. We have now demonstrated by in situ hybridization, immunohistochemistry, and topical autoradiography that the adult rat spinal cord expresses hCG/LH receptors. Positive cells included motoneurons, interneurons and/or glia in the intermediate and ventral gray matter, interneurons and/or glia in the dorsal gray matter, and oligodendrocytes or astrocytes in the white matter. The receptors were able to bind an appropriate ligand, (125)I-hCG. The functional significance of these receptors in the spinal cord is unknown, but we can speculate that they may be neurotrophic in function.

Expression and localization of the contractile prostaglandin F receptor in pregnant rat myometrium in late gestation, labor, and postpartum

A polyclonal antibody was raised against amino acids 7-18 in the first extracellular loop of rat prostaglandin F (FP) receptor to monitor expression and localization in pregnant rat myometrium at Gestational Days 16, 18, 20, 21, 21.5, 22 (delivery), and 23 (1-day postpartum; n = 5 per group). The antibody recognized a protein of approximately 43 kDa on Western blot analysis in both membrane (soluble and nonsoluble) and cytosolic fractions of myometrium on each day of gestation. Expression of FP protein increased significantly (P < 0.05) during late gestation in both soluble membrane and cytosolic fractions, being significantly greater at Day 21.5 than at Day 20 of gestation in the soluble membrane fraction and in the cytosolic fraction of tissues collected during labor compared with those obtained before labor. The total concentration of FP receptor in the membrane (soluble plus nonsoluble) remained high throughout late gestation and fell significantly (P < 0.05) in the postpartum period. The FP receptor in the soluble membrane fraction (compared to the total membrane FP receptor) was significantly (P < 0.05) higher in late gestation than earlier, whereas the ratio of FP protein in cytosolic to that in the total membrane was significantly (P < 0.05) higher on Day 23 than earlier in gestation, suggesting a dynamic movement of FP with advancing gestational age. Immunoreactive FP receptor localized to circular and longitudinal smooth muscle at all gestational ages, but changes in intracellular localization were observed in late gestation with a staining pattern similar to alpha-actin, suggesting an association with myofibrils. Our study suggests an increase in FP-receptor protein in myometrium with advancing gestation and a marked elevation at term. This supports a role for uterine FP receptors in mediation of uterine contractility at term.

Arachidonic acid metabolism by nuclei of a retinoic acid--or vitamin D3-differentiated human leukemia cell line HL-60

Arachidonic acid (AA) metabolism in nuclei of human pro-myelocytic leukemia (HL-60) cells was investigated during retinoic acid (RA)-induced granulocytic differentiation and 1 alpha, 25 dihydroxy-vitamin D3-induced monocytic differentiation. The whole control HL-60 cells and their nuclei hardly converted [1-14C]-AA to any metabolites comigrating with authentic prostaglandins (PGs). On the other hand, RA-treated HL-60 cells acquired the ability to convert [1-14C]-AA to PGE2 predominantly and thromboxane B2 (TXB2) to a small degree, whereas the nuclei of the differentiated cells acquired the ability to convert predominantly to TXB2. In contrast, 1 alpha, 25-dihydroxy-vitamin D3-treated HL-60 cells acquired the ability to convert [1-14C]-AA to PGE2, PGF2 alpha, TXB2 and 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT), whereas the nuclei of the differentiated cells acquired the ability to convert to PGF2 alpha, TXB2 and HHT. The significance of the acquisition of cyclooxygenase and TX synthetase by the nucleus is unclear, but there may be a specific relationship between the specific PGs formed by the nuclear membrane and nuclear events during HL-60 cell differentiation.

Introduction of a gonadotropin receptor expression plasmid into immortalized granulosa cells leads to reconstitution of hormone-dependent steroidogenesis

We have recently succeeded in immortalizing rat granulosa cells by co-transfection with SV-40 DNA and the Ha-ras oncogene. These cells lost their response to gonadotropins, but expressed the cytochrome P450scc mitochondrial system enzymes and produced progesterone and 20 alpha-hydroxy-4-pregnan-3-one (20 alpha-OH-P) upon cAMP stimulation (Suh, B. S., and A. Amsterdam. 1990. Endocrinology. 127:2489-2500; Hanukoglu, I., B. S. Suh, S. Himmelhoch, and A. Amsterdam. 1990. J. Cell Biol. 111:1973-1981). In an attempt to restore the steroidogenic response to gonadotropins in immortalized cells, lutropin/choriogonadotropin (LH/CG-R) receptor expression plasmid was prepared by introducing the complete coding region of LH receptor cDNA (McFarland, K. C., R. Sprengel, H. S. Phillips, M. Köhler, N. Rosemblit, K. Nikolics, D. L. Segaloff, and P. H. Seeburg. 1989. Science (Wash. DC). 245:494-499) into a SV-40 early promoter based eucaryotic expression vector. Granulosa cells from preovulatory follicles were transfected with this LH receptor expression plasmid, together with SV-40 DNA and the Ha-ras oncogene. Cell lines obtained after this triple transfection accumulated cAMP in a dose-dependent manner in response to hCG. Moreover, they produced progesterone and 20 alpha-OH-P upon hCG stimulation with an ED50 of 125 pM and 75 pM, respectively, which is within the physiological range. Concomitantly with hCG induced differentiation, inhibition of cell proliferation was evident following stimulation with hormone concentrations as low as 40 pM. The number of hCG receptor sites per cell after numerous passages and several freezing and thawing cycles was 1.9 x 10(4), they showed a Kd of 180 pM. Stimulation with hCG induced pronounced morphological and biochemical changes in these cells including formation of mitochondrial located adrenodoxin, a marker enzyme for enhanced steroidogenesis. These findings make possible the expression in immortalized granulosa cells, of selectively mutated receptor molecules which preserve their steroidogenic potential, thereby opening the way to analysis of structure-function relationships of the receptor molecule.

Light and electron microscopic localization of retrogradely transported neurotensin in rat nigrostriatal dopaminergic neurons

We previously demonstrated the existence of a retrograde axonal transport of radioactivity to the substantia nigra pars compacta following injection of mono-iodinated neurotensin in rat neostriatum. In the present study, the topographical and cellular distribution of this retrogradely transported material was examined by light and electron microscopic autoradiography. Four and a half hours after unilateral injection of [125I]neurotensin in the caudoputamen, retrogradely labelled neuronal cell bodies were detected by light microscopic autoradiography throughout the ipsilateral substantia nigra pars compacta as well as within the ventral tegmental area and retrorubral field. In semithin sections, silver grains were prevalent over the perinuclear cytoplasm of neuronal cell bodies but were also detected over neuronal nuclei. Analysis of electron microscopic autoradiographs revealed that the vast majority (greater than 85%) were associated with neuronal perikarya, unmyelinated and myelinated axons, dendrites and terminals. Within the soma, a significant proportion of silver grains (16% of somatic grains) was detected over the nucleus. However, the majority were identified over the cytoplasm where they often encompassed cytoplasmic organelles, including rough endoplasmic reticulum, mitochondria, Golgi apparatus, lysosomes, and multi-vesicular bodies. In dendrites and axons, a substantial percentage of silver grains (63-89%) was localized over the plasma membrane. A minor proportion (13% of total) of the autoradiographic labelling was detected over myelin sheaths, astrocytes, and oligodendrocytes. The present results are consistent with previous light-microscopic evidence for internalization and retrograde transport of intrastriatal neurotensin within nigrostriatal dopaminergic neurons. They further suggest that retrogradely transported neurotensin may be processed along a variety of intracellular pathways including those mediating degradation in lysosomes and recycling in rough endoplasmic reticulum. The detection of specific autoradiographic labelling in the nucleus supports the concept that neurotensin alone, or complexed to its receptor, might be involved in the regulation of gene expression through direct or indirect interactions with nuclear DNA. Consequently, the retrograde transport of neurotensin in nigrostriatal dopaminergic neurons might provide a vehicle through which events occurring at the level of the axon terminal may initiate long-term biological responses.

Nuclear volume and chromatin conformation of small and large bovine luteal cells: effect of gonadotropins and prostaglandins and dependence on luteal phase

Change in nuclear volume and chromatin conformation are generally considered to reflect altered gene expression in eukaryotic cells. The present studies were undertaken to investigate whether these nuclear parameters of luteal cells can be altered by hormone treatment in vitro or change during the estrous cycle. The nuclear volume of small luteal cells was significantly lower than that of large luteal cells during the cycle and pregnancy. The nuclear volumes of small and large luteal cells from pregnancy did not change during incubation without any hormone or with 10 nM prostaglandin (PG)F 2 alpha. However, incubation with 1 nM human chorionic gonadotropin (hCG) or 10 nM PGE1 resulted in a significant increase of nuclear volume of small luteal cells by 4 h and that of large luteal cells by 6 h. Small luteal cells were more responsive to hCG than large luteal cells. The nuclear volumes of small and large luteal cells also significantly increased from early to mid luteal phase with no further change in late luteal phase. hCG and PGE1, as well as PGF2 alpha, treatment resulted in a change of chromatin conformation of small and large luteal cells. Dibutyryl cyclic AMP (10 mM) mimicked the hormones by increasing nuclear volumes and changing the chromatin conformation of small and large luteal cells. Chromatin conformation of small and large luteal cells also changed from early to mid luteal phase and mid to late luteal phase. In conclusion, in vitro, hCG and PGs can regulate nuclear volume and/or chromatin conformation of small as well as large bovine luteal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of luteal cell nucleus in the expression of gonadotropin action

Gonadotropin receptors are not only present in cell membranes, but also in nuclei of bovine and human luteal cells. hCG/hLH can directly regulate several nuclear functions. To further investigate the role of luteal cell nucleus in the expression of gonadotropin action, the effect of enucleation of luteal cells on gonadotropin receptors and gonadotropin response was studied. Luteal cytoplasts were prepared by colchicine treatment of purified whole luteal cells followed by centrifugation at 37 C in a Percoll gradient. The cytoplasts were 85 to 90% pure with a recovery of about 57%. Cytoplasts were viable as determined by trypan blue exclusion (87%) and metabolically competent as determined by 3H-leucine incorporation into proteins. On the day of preparation, the viability and metabolic competency of cytoplasts were similar to control cells, i.e. untreated and colchicine treated whole luteal cells. In addition, cytoplasts and control cells showed a similar decline in number and viability during storage at 4 C. While control cells continue to be metabolically competent, cytoplasts showed a dramatic decline by 48 h of storage at 4 C. Neither the cytoplasts nor control cells degraded 125I-hCG. The kinetics of 125I-hCG association and dissociation, specificity and affinity of binding to cytoplasts were similar to control cells. However, the number of available gonadotropin receptors in cytoplasts was significantly lower than in control cells. Cytoplasts contained lower progesterone levels and more importantly, they could not be stimulated by 10 nM hCG or 10 mM dibutyryl cyclic AMP to produce more progesterone. Controls cells, on the other hand, contained higher progesterone levels and responded to hCG and dibutyryl cyclic AMP stimulation. In summary, removal of nuclei from luteal cells results in a partial loss of gonadotropin receptors and complete loss of steroidogenic response to hCG and dibutyryl cyclic AMP.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effects of cytokines on prostaglandin E and cAMP levels in human periodontal ligament fibroblasts in vitro

The stimulation of PGE synthesis and cAMP production by cytokines have important physiological effects in many target tissues. The effects of interleukin-1 alpha and -1 beta, tumour necrosis factor-alpha and interferon-gamma on PGE and cAMP production by periodontal ligament fibroblasts were studied. Fibroblasts in the 4th-6th passage, grown and maintained in DMEM supplemented with 10% equine serum, were incubated with graded doses of the various cytokines for 0.25, 0.5, 1.2, 4, 24, 48 or 72 h. At the end of each incubation, PGE in the medium and the cellular content of cAMP were evaluated by a combined immunohistochemical microphotometric procedure, and conventional radiometric assays. The fibroblasts responded to all the cytokines with a dose- and time-related increase in the levels of PGE and cAMP. Such increases were inhibited by the inclusion of indomethacin in the medium. The addition of exogenous PGE reversed that inhibition in respect of cAMP production. Immunohistochemical localization showed PGE predominantly in the cytoplasm and cAMP in the nucleus. These findings indicate that: (1) human periodontal ligament fibroblasts respond to these cytokines by increased synthesis of PGE and the production of cAMP; and (2) the cAMP production is secondary to the PGE synthesis. They suggest that these cytokines may regulate the function of these fibroblasts in physiological remodelling of the periodontium, as well as in inflammatory reactions.

Immunohistochemical assessment of the effect of chemical and mechanical stimuli on cAMP and prostaglandin E levels in human gingival fibroblasts in vitro

These were evaluated by: (1) a combined immunohistochemical-microphotometric procedure (IH) and (2) conventional radiometric assays. Human gingival fibroblasts were in the sixth passage, grown and maintained in Dulbecco minimal essential medium (DMEM) supplemented with 10 per cent horse serum. For chemical and hormonal stimuli, cells (2 x 10(4] were seeded on tissue-culture chamber/slides, and incubated with graded doses of either parathyroid hormone (PTH) or prostaglandin E2 (PGE2) for assessment of their adenosine-3',5'-monophosphate (cAMP) levels, and with indomethacin or colchicine for their effect on PGE levels. For mechanical stimuli, cells (1 x 10(6] were seeded on culture dishes with a flexible plastic membrane and stretched for 5, 30, 60 or 120 min by placing the membrane over a convex surface and weighting the dish cover. After freeze drying, cells were stained by an immunoperoxidase technique for either cAMP or PGE, using monoclonal antibodies. The staining intensity of fibroblasts was determined at 600 nm wavelength. Per cent light absorbance of 15 cells in each slide was measured and the results tested by analysis of variance. The gingival fibroblasts responded to the drugs and hormones in a dose- and time-related fashion. Stretching significantly increased their synthesis of PGE with concomitant increase in cAMP. The IH results were compared with the radiometric assays to confirm the validity of this technique; both assays were valid for describing the quantitative responses of these cells to the stimuli. In particular, the IH method could localize those intracellular sites which demonstrated chances in relative cAMP and PGE concentrations in response to hormonal stimuli.

Homologous regulation of prostaglandin E2 receptors in rat renal medulla

Prostaglandin (PG) receptors are present on enzymatically dissociated cells from the rat renal medulla and are subject to homologous regulation both in vivo and in vitro. One hour after injection of 100 micrograms of 16,16'-dimethyl-PGE2, the number of PGE2 binding sites on renal cells declines to 40% of controls. In vitro exposure of renal cells to PGE2 or dimethyl-PGE2 also results in a time- and concentration-dependent "down" regulation of prostaglandin receptors. In the absence of indomethacin in the incubation medium, endogenously synthesized prostaglandins mediate a similar time-dependent loss of cell-associated receptors. This loss is reversible since, after agonist removal and reincubation of the cells at 37 degrees C, there is a rapid (within 15 min) reappearance of PGE2 receptors (to 60-93% of controls). Reappearance occurs whether down regulation is induced in vitro by endogenously synthesized prostaglandins, added PGE2 or dimethyl-PGE2, or in vivo after injection of dimethyl-PGE2. Cycloheximide does not affect down regulation but significantly prevents subsequent recovery of the receptors. In contrast, neither colchicine nor chloroquine influences homologous regulation of renal prostaglandin receptors. These results document an agonist-induced reversible cycling of renal prostaglandin receptors which may determine the effectiveness of prostaglandin action in normal and pathologic states.

Inhibitory effect of prostaglandin D2 on DNA synthesis in nuclei

Prostaglandin (PG) D2 treatment inhibited DNA synthesis in isolated nuclei of mastocytoma P-815, 2-E-6 cells. On treatment with PGD2 (10 micrograms/ml), the inhibition was distinct by 8 hrs, and complete after 18 hrs. This effect of PGD2 on DNA synthesis in nuclei was not direct or mediated by cyclic AMP, but was a cell-mediated reaction. The cytoplasmic fractions of PGD2-treated and untreated cells both had stimulatory effects and their potencies were the same except for that of the cytoplasmic fraction of 8 hr-treated cells, which was less than that of the cytoplasmic fraction of untreated cells. On treatment with PGD2, inhibition of DNA synthesis in the nuclei began after 8 hrs, and this inhibition could not be reversed, even by adding the cytoplasmic fraction from untreated cells to the assay system. A nuclear salt extract prepared by adding 0.3 M NaCl to nuclei of cells that had been treated with PGD2 for 18 hrs had a much smaller stimulatory effect on DNA synthesis of salt-treated nuclei than an extract of nuclei from untreated cells. It is suggested that inhibition of cell growth by PGD2 is not mediated by intracellular cyclic AMP, but that PGD2 induces a factor(s) that inhibits nuclear DNA synthesis.

Up-regulation of renal prostaglandin receptors in genetic salt-dependent hypertension

Development of hypertension in Dahl salt-sensitive rats (DS) is accompanied by reduced renomedullary prostaglandin synthesis, which may be responsible for their lower natriuretic capacity. To examine the changes in renomedullary prostaglandin E2 synthesis, the effects of high (8.0%) and normal (0.6%) NaCl diets were examined in DS and in Dahl salt-resistant rats (DR). In response to an 8.0% NaCl diet, the number of prostaglandin E2 receptors in the renal outer medulla of DR increased (2.97 +/- 0.2 vs 2.18 +/- 0.2 pmol/mg on 0.6% NaCl diet) while no change was noted in their affinities (Kd, 9.5 +/- 0.2 vs 9.4 +/- 0.3 nM). Receptor number and affinity in the renal cortex, inner medulla, and liver of DR were not affected. In contrast, renomedullary receptors of DS had a lower affinity than those of age-matched DR (Kd, 13.9 +/- 0.2 nM on 0.6% NaCl diet and 14.0 +/- 0.3 nM on 8.0% NaCl diet) and did not increase in number after a high salt diet. This apparent inability of DS to modulate prostaglandin receptors may contribute to their susceptibility to salt-induced hypertension.

Prostaglandin binding to different cell types of human uterus: quantitative light microscope autoradiographic study

Five human uteri of the menstrual cycle were analyzed by quantitative light microscope autoradiography to determine which uterine cell types contain prostaglandin (PG) binding sites. The results showed that stromal cells, glandular epithelium, elongated and circular smooth muscles, arterioles and erythrocytes in lumen of arterioles contained numerous PGE and very few or no detectable PGF2 alpha binding sites. The grains which were present when incubated with [3H]PGE2 alone completely disappeared following coincubation with excess unlabeled PGE2 but not with excess unlabeled PGA1. Analysis of grain count data revealed that PGE binding sites in arterioles were lower than those in other uterine cell types and PGE binding sites in endometrial cells of proliferative phase uteri were higher than those in secretory phase uteri (P less than 0.05). Thus the present results demonstrate that all the cell types, including arterioles of human uterus of the menstrual cycle, contain PGE and minimal PGF2 alpha binding sites. This suggests that PGE binding sites in different cell types of human uterus subserve diverse effects of PGEs.

Prostaglandin receptors in rat kidney

The physiological effects of prostaglandins (PGs) are mediated through their interactions with specific binding sites (receptors) on effector cells. Since such receptors potentially regulate the action of PGs on the kidney, the distribution and properties of renal PG receptors in the rat were examined. The distribution of PGE2, PGE1, and PGF2 alpha receptors along the nephron was not uniform; the outer medulla had by far the greatest density of sites, followed by the inner medulla and cortex. Receptors were found exclusively in the particulate fractions, of which the 40,000g pellet had the highest specific activity. In the outer medulla, receptor density calculated from Scatchard plots was 2.12 pmol/mg for PGE2, 1.12 for PGE1, and 0.44 for PGF2 alpha; the KD's were similar for all prostaglandins. The conditions for optimal in vitro binding of PGE2 and PGF2 alpha by outer medullary membranes were investigated. In vivo administration of 16,16'-dimethyl-PGE2 resulted in a dose-dependent "down" regulation of PGE2 binding to outer medullary membranes due to changes in both the number and affinities of receptors. Changes in the numbers and/or properties of PG receptors may be an important mechanism for regulating the effects of PGs and renal function under normal and pathologic conditions.

Internalization of 125I-human choriogonadotropin in bovine luteal slices. A biochemical study

Various intracellular organelles as well as outer cell membranes of bovine corpora lutea intrinsically contain gonadotropin receptors (Rao et al., J biol chem 256 (1981) 2628 [5]). In order to investigate whether exogenously added human choriogonadotropin (hCG) can internalize and bind to the intracellular sites, bovine luteal slices that had been carefully checked with respect to structural and functional integrity were incubated with 0.1 nM 125I-hCG. Following incubation, specific radioactivity was found to be associated with various intracellular organelles, but not with cytosol. The order of radioactivity uptake by subcellular organelles following a 2-h incubation was: Golgi medium greater than Golgi heavy greater than Golgi light greater than plasma membranes = rough endoplasmic reticulum greater than mitochondria-lysosomes- greater than nuclei. The 5'-nucleotidase activity and electron microscopic examination of the fractions revealed that the presence of radioactivity in the intracellular organelles cannot be attributed solely to plasma membrane contamination. The internalization and intracellular binding of 125I-hCG was time and temperature-dependent. Only excess unlabeled hCG and hLH (but not hCG subunits, FSH and PRL) competed with 125I-hCG for internalization in luteal slices. Very little or no 125I-hCG added was internalized in liver or kidney slices; luteal, liver and kidney slices accumulated neither 125I-BSA nor 125I. The radioactivity eluted from various luteal subcellular organelles was able to rebind to fresh corresponding organelles and came off Sepharose 6B columns in a position corresponding to native 125I-hCG. The gel filtration profile of detergent-solubilized radioactivity revealed that 125I-hCG was macromolecular bound. The degraded and altered 125I-hCG was found in the incubation media.

A quantitative electron microscope autoradiographic study on 125I-human choriogonadotropin internalization in bovine luteal slices

Very few silver grains were seen on the cell surface and none intracellularly after incubation for 2 h at 4 degrees C. However, numerous grains were seen in various subcellular organelles when the tissues were incubated for 2 h at 22 degrees or 38 degrees C. The grain distribution was qualitatively similar, but quantitatively, there were fewer grains at 22 degrees than at 38 degrees C. Co-incubation of 125I-hCG with excess unlabelled hCG resulted in the virtual disappearance of silver grains from all the subcellular organelles. Excess unlabelled human luteinizing hormone (but not follicle-stimulating hormone or prolactin) inhibited the appearance of silver grains in luteal tissue. There were no silver grains in bovine liver slices incubated with 125I-hCG. The plasma membrane-associated grains progressively decreased, while intracellular organelle-associated grains increased with time at 38 degrees C. There were no grains in nuclei at 5 min, but they appeared at 10 min and increased until 120 min. After correction for radiation spread by three-step mask analysis, smooth endoplasmic reticulum and mitochondria did not contain any grains. The grain density was the highest in Golgi, followed by lysosomes, rough endoplasmic reticulum, nuclei, and plasma membranes after incubation for 2 h at 38 degrees C. Thus, the electron microscope autoradiography approach confirmed our biochemical data in the preceding paper (Chegini et al., Exp cell res 151 (1984) 466 [5]) on time, temperature dependency and specificity of 125I-hCG internalization, association of internalized hormone with a variety of intracellular organelles, and the highest uptake in Golgi.

Interrelationships among prostaglandins, vasopressin and cAMP in renal papillary collecting tubule cells in culture

To determine the influence of prostaglandins on cAMP metabolism in renal papillary collecting tubule (RPCT) cells, intracellular cAMP levels were measured after incubating cells with prostaglandins (PGs) alone or in combination with arginine vasopressin (AVP). PGE1, PGE2 and PGI2, but not PGD2 or PGF2 alpha, increased intracellular cAMP concentrations. At maximal concentrations (10(-5) M) the effects of PGE2 plus PGI2 (or PGE1), but not of PGI2 plus PGE1, were additive suggesting that at least two different PG receptors may be present in RPCT cell populations. Bradykinin treatment of RPCT cells caused an accumulation of intracellular cAMP which was blocked by aspirin and was quantitatively similar to that observed with 10(-5) M PGE2. PGs, when tested at concentrations (e.g. 10(-9) M) which had no independent effect on intracellular cAMP levels, did not inhibit the AVP-induced accumulation of intracellular cAMP in RPCT cells. These results indicate that PGs do not block AVP-induced accumulation of intracellular cAMP in RPCT cells at concentrations of PGs which have been shown to inhibit the hydroosmotic effect of AVP on perfused collecting tubule segments. However, at higher concentrations of PGs (e.g. 10(-5) M), the effects of AVP plus PGE1, PGE2, PGI2 or bradykinin on intracellular cAMP levels were not additive. Thus, under certain conditions, there is an interaction between PGs and AVP at the level of cAMP metabolism in RPCT cells.

The presence of gonadotropin binding sites in the intracellular organelles of human ovaries

The nuclei (N), plasma membranes (PM), mitochondria-lysosomes, rough endoplasmic reticulum, and combined (light, medium, and heavy) Golgi (G) fractions were isolated from human ovaries. The purities of these fractions were evaluated by assays of appropriate marker enzymes, which revealed that some fractions were very pure but that others had minor contamination. When tested, all of the fractions exhibited 125I-labeled human chorionic gonadotropin (125I-hCG)-specific binding. This intracellular 125I-hCG binding was not due to PM contamination because: (1) N, which had no detectable 5'-nucleotidase (5'-NE) activity, a marker for PM, exhibited 125I-hCG-specific binding; (2) the G, which had only a fraction of the 5'-NE activity of PM, exhibited as much binding as PM; and (3) the ratios between specific 125I-hCG binding and 5'-NE activity in other fractions were not the same as for PM. They should have been the same if PM contamination was responsible for the 125I-hCG binding observed in other organelles. In conclusion, our results demonstrate that gonadotropin-binding sites are present in various intracellular organelles as well as in PM of human ovaries.