Biomedical subjects

N Chegini

Publications and source records attributed to N Chegini.

At least 109 records · Page 6Linked to original sources

PubMed1988

Quantitative light microscopic autoradiographic study on [3H]leukotriene C4 binding to nonpregnant bovine uterine tissue.

Mammalian uteri contain both lipoxygenase and cyclooxygenase pathways of arachidonic acid metabolism. Sulfidopeptidyl leukotrienes formed by the lipoxygenase pathway can stimulate uterine contractions and play a role in uterine preparation for implantation. These actions of leukotrienes are perhaps mediated by binding to specific receptors. To understand the cellular basis of leukotriene C4 action, the present quantitative light microscopic autoradiographic study was undertaken on nonpregnant bovine uterine tissue. The results demonstrated that the circular and elongated myometrial smooth muscle, uterine vascular smooth muscle, stromal cells of endometrium, and fibroblasts of perimetrium, but not the endometrial glands, vascular endothelium, and erythrocytes in lumen of arterioles, contained specific silver grains after incubation with [3H]leukotriene C4. The number of grains per 100-micron2 areas were similar in circular and elongated myometrial smooth muscle (P greater than 0.05), which was higher than in other uterine cells (P less than 0.05-0.01). The grains in all cells were greatly reduced after coincubation with excess unlabeled leukotriene C4, but not with leukotriene A4, leukotriene B4, leukotriene D4, leukotriene E4, prostaglandin E2, prostaglandin F2 alpha, or prostacyclin. In conclusion, leukotriene C4 may regulate both uterine cells and uterine vasculature and exert contractile and noncontractile actions via the specific leukotriene C4-binding sites present in different cell types.

Animals↗

PubMed1988

The presence of leukotriene C4- and prostacyclin-binding sites in nonpregnant human uterine tissue.

Human uterine tissue can synthesize leukotrienes and prostacyclin (PGI2) from arachidonic acid via the lipoxygenase and cyclooxygenase pathways, respectively. Leukotriene C4 stimulates myometrial and vascular smooth muscle contractions, whereas PGI2 inhibits them. In addition, these eicosanoids have other actions in uterine tissue. All of these actions are possibly mediated by specific receptors, but such receptors have not been demonstrated in human uterine tissue. Therefore, these quantitative light microscopic autoradiographic studies were undertaken to determine whether nonpregnant human uterine tissue contains specific leukotriene C4- and PGI2-binding sites. Studies with [3H]leukotriene C4 indicated that luminal epithelial cells of the endometrium, stromal cells, elongated and circular myometrial smooth muscle, and arteriolar smooth muscle contained numerous binding sites. Glandular epithelium, vascular endothelium, and erythrocytes, on the other hand, contained few or no leukotriene C4-binding sites. The number of binding sites in luminal epithelial cells of the endometrium was as high as that in lung, which is a rich source of these binding sites. The number of binding sites in these epithelial cells was higher (P less than 0.05) than that in stromal cells, circular myometrial smooth muscle, and arteriolar smooth muscle, but there were no significant (P greater than 0.05) differences among other cells. Maximal binding occurred at 5 min of incubation at 22 or 38 C. The presence of serine borate, a gamma-glutamyl transpeptidase inhibitor, in the incubation medium resulted in a small to moderate increase in leukotriene C4 binding to uterine cells. Binding to the cells was significantly (P less than 0.001) reduced after coincubation with excess unlabeled leukotriene C4, but not with excess unlabeled leukotriene A4, leukotriene B4, leukotriene D4, leukotriene E4, prostaglandin (PG) E1, PGF2a, or PGI2. Studies with [3H]PGI2 demonstrated that while myometrium and vascular smooth muscle contained PGI2-specific binding sites, endometrium and vascular endothelium contained very few or no binding sites. Elongated myometrial smooth muscle contained a higher number of binding sites than circular myometrial smooth muscle and vascular smooth muscle (P less than 0.01). PGI2 binding to the uterine cells was dependent on the time and temperature of incubation, and Ca2+ was not required for binding. Coincubation with unlabeled PGI2, but not with its stable metabolite 6-keto-PGF1a, resulted in a significant reduction (P less than 0.001) of binding to uterine cells. PGE2, PGF2a, and leukotriene C4 also had no effect on [3H]PGI2 binding.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Effects of bacterial infection on absorbable vascular ligating clips.

Electron microscopic observations of two implanted absorbable clips, Absolok and Lactomer, infected with Escherichia coli and Streptococcus faecalis, were carried out. An overgrowth of bacteria was observed over the entire surface of the clips. The mating surfaces of the Lactomer clips and the locking mechanisms of both types of clip were more heavily infected--that is, provided better support for bacterial growth--than other areas of the clips in the initial postimplantation period. However, with longer periods (up to seven days), the initial bacterial deposits developed into a thick, plaquelike layer. This layer appeared to restrict access to the surfaces such that the infected clips degraded at a much slower rate than did the noninfected clips, particularly Lactomer clips, on which little morphologic change was detectable seven days after implantation.

Animals↗

PubMed1988

Tissue reactions to absorbable ligating clips.

Scanning electron microscopy was used in a comparative ultrastructural study of biodegradable ligating clips, the Absolok (polydioxanone) and the Lactomer (copolymer of glycolic and lactic acids), implanted subcutaneously in rabbits. The inflammatory response and tissue reactions to the implanted clips and their effects on clip breakdown were studied. By the first week after implantation, numerous inflammatory cells adhered to the clip surfaces, with occasional fibroblasts present. By two weeks after implantation there was a reduction in the number of inflammatory cells, but the number of fibroblasts gradually increased, resulting in encapsulation of the clips. The thickness of the fibrous tissue capsule, formed by a variety of collagen fibers, gradually increased 5-25 weeks after implantation. Residues from the Lactomer clips were still present within the encapsulating tissue at 25 weeks. In contrast, clips enclosed in nylon pouches were totally degraded, and no residues were detectable at 25 weeks. Tissue reactions similar to those observed for nonpouched implanted clips were seen over the entire external surface of the pouches.

Animals↗

PubMed1987

Morphological alterations induced by prostaglandins E1, F2 alpha and A1 in MDA-MB-231 and MCF-7 human breast cancer cell lines.

Monolayer cultures of MDA-MB-231 and MCF-7 human breast tumor cell lines were treated with prostaglandins PGE1, PGF2 alpha and PGA1 in a concentration range of 10(-12)-10(-4) M and studied at ultrastructural level. Electron microscopic examinations of both cell lines revealed that PGE1, PGF2 alpha and PGA1 induced morphological changes at concentrations above 10(-8) M. In both the small and large MDA-MB-231 cells, deformation of mitochondrial cristae, increased density of mitochondrial matrix and accumulation of lysosomal-like vesicles were observed. In the nuclei morphological, modifications included, the presence of nuclear bodies, occasional nuclear inclusions, nucleolar budding and the disappearance of the nucleolar granular components. In MCF-7 cells, disorganization of mitochondrial cristae and an increase in their matrix density were also observed. At nuclear level, little or no morphological alterations were observed. The results also indicated that the plasma membranes of both cell lines were the most sensitive organelles to PGs action as in many cells their microvilli were either shortened and spherical in shape or absent.

Alprostadil↗

PubMed1987

The use of nylon pouches to prevent cellular attachment to implanted materials.

A nylon pouch system has been developed to permit the in vivo exposure of implantable materials to tissue fluids without complications arising from cellular attachment or from the bacterial attack. SEM observations have indicated that the pouches were effective in reducing the ingress of bacteria as well as reducing, and in some cases eliminating, cell infiltration through their mesh structure. Over a 7 d implantation period, the exterior surfaces of the nylon pouches were heavily infested with microorganisms but there was minimal growth of bacteria within the pouches. Non-infected pouches that were implanted for up to 25 wk showed heavy deposits of cellular matter on the external surfaces of the pouches and minimal deposits within the pouches.

Absorption↗

PubMed1987

Influence of mitoxantrone on nucleolar function in MDA-MB-231 human breast tumor cell line.

The effect of mitoxantrone (DHAQ) on [3H]thymidine and [3H]uridine incorporation by exponentially growing MDA-MB-231, a human breast tumor cell line has been studied. The results have indicated that DHAQ was more effective in inhibiting [3H]thymidine than [3H]uridine incorporation in a concentration dependent manner. Following drug treatment at 20 ng/ml concentration, 50% inhibition of growth and [3H]thymidine incorporation were noted, whereas [3H]uridine incorporation was only inhibited by about 12%. At 2000 ng/ml of DHAQ the inhibition of cell growth, [3H]thymidine and [3H]uridine incorporations were 78%, 95% and 62%, respectively. Nuclear-associated radioactivity detected at light and electron microscope autoradiographic levels after [3H]thymidine and [3H]uridine incorporations, into DHAQ treated cells indicated that DHAQ prevented the accumulation of radioactivity into the nuclei in a concentration dependent manner. These results gave further indication that mitoxantrone induced a definitive alteration of nuclear template activities, correlated with nuclear functional-structural relation and suggested that the nucleoli were the primary site of DHAQ action.

Autoradiography↗

PubMed1987

Dynamics of nuclear associated granules in bovine luteal cells after treatment in vitro with prostaglandin F2 alpha.

A group of electron-dense granules of 150-300 nm in diameter, with a single limiting membrane, were found adjacent to the nuclei of large (25-50 microns in diameter), but not small (15-22 microns), bovine luteal cells of pregnancy. These granules were quite heterogeneous with respect to size, shape, content, etc. Most granules contained varying amounts of light and dark electron-dense material, and very few contained only light or dark material in their core. These granules occupied 160.4 +/- 7.8 microns3 cytoplasmic volume, which did not significantly decrease until 2 h of incubation without any hormone at 22 or 38 C (P greater than 0.05). Subsequently, however, volume occupancy of these granules decreased to 127.3 +/- 6.4 and 117.6 +/- 8.0 microns3 (P less than 0.05) by 4 and 12 h of incubation, respectively. Incubation of luteal tissue with 10 nM prostaglandin F2 alpha (PGF2 alpha), on the other hand, resulted in a decrease to 124.4 +/- 8.0 microns3 of volume occupancy of granules by 10 min (P less than 0.05). The volume occupancy further decreased to 46.2 +/- 4.8 microns3 by 2 h (P less than 0.01), and then the granules virtually disappeared from luteal cells. While PGF2 alpha decreased volume occupancy of granules similarly at 22 and 38 C, it had no effect at 4 C. PGF2 alpha decreased volume occupancy of granules at 0.01 nM (P less than 0.05), which continued to decrease with increasing PGF2 alpha concentrations, reaching a maximal decrease at 10 nM PGF2 alpha (P less than 0.05). PGE1, hCG, human LH, human PRL, or (Bu)2cAMP had no effect on the granules, suggesting that the PGF2 alpha effect was hormone specific. PGE1 and hCG, which protect corpus luteum from the luteolytic action of PGF2 alpha, could not inhibit degranulation by PGF2 alpha. These results demonstrate that treatment with PGF2 alpha in vitro results in a decrease in volume occupancy of nuclear associated granules in bovine large luteal cells of pregnancy in a time-, temperature-, and concentration-dependent and hormone-specific manner.

Alprostadil↗

PubMed1987

Alterations of MCF-7 human breast cancer cell after prostaglandins PGA1 and PGF2 alpha treatment.

Treatment of monolayer cultures of MCF-7 cells with prostaglandins PGA1 and PGF2 alpha inhibited cell proliferation, reduced the rate of labeled precursor incorporation into DNA, RNA, and protein, and induced morphological changes in a dose-dependent manner. The rate of [3H]thymidine incorporation was increased by PGA1 at 10(-10)-10(-8) M, while a sharp decrease was observed at 10(-6)-10(-4) M (p less than 0.05 and p less than 0.005). PGF2 alpha inhibited [3H]thymidine incorporation at all concentrations tested. Similar results were obtained for [3H]uridine incorporation with both PGs. PGA1 inhibited [3H]leucine incorporation at 10(-4) M, but increased incorporation at 10(-10)-10(-6) M. At the ultrastructural level, neither PG induced morphological alterations at 10(-12)-10(-8) M. However, at 10(-6)-10(-4) M both PGA1 and PGF2 alpha diminished the number and size of cell surface projections; some cells appeared to completely lack microvilli. Disorganization of mitochondrial cristae and increased electron density of the matrix were also evident.

Breast Neoplasms↗

PubMed1986

Binding of 125I-epidermal growth factor in human uterus.

Quantitative light-microscopic autoradiography was used on five human uteri at two different phases of the menstrual cycle to ascertain the cell types with binding sites for epidermal growth factor (EGF). The results revealed that stromal cells, glandular epithelium of endometrium, elongated and circular muscle cells of myometrium, smooth muscle and endothelial cells of arterioles in the basal endometrium and myometrium contained numerous silver grains following incubation with 125I-EGF. Coincubation with 100-fold excess unlabeled EGF resulted in a complete disappearance of silver grains from all cell types. Quantitative grain analysis indicated that stromal cells contained the highest number of EGF-binding sites (P less than 0.05) with no significant differences among the others (P greater than 0.05). There was no cyclic variation of EGF-binding to any of the uterine cell types. The present data demonstrate that all the cell types of human uterus, including arterioles, contain EGF-binding sites. This suggests that all the cells in human uterus subserving different functions are targets of EGF action.

Arterioles↗

PubMed1986

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.

Arterioles↗

PubMed1986

The presence of epidermal growth factor binding sites in the intracellular organelles of term human placenta.

Highly purified lysosomes, rough and smooth endoplasmic reticulum, and Golgi apparatus, as well as microvillus plasma membranes, bound 125I-labelled epidermal growth factor ([125I]EGF) with similar affinity. Scatchard plots for all the organelles were curvilinear. The apparent number of available binding sites per mg protein of intracellular organelles was 27-71% of that found in microvillus plasma membranes. The bound and free [125I]EGF were not degraded by any of the organelles. Binding and dissociation of [125I]EGF in all organelles were dependent on the time and temperature of incubation. The specificity of [125I]EGF binding was similar in all organelles. The optimal pH for binding to lysosomes was 6.0, in contrast to 7.0 for all the other organelles. Exposure of different organelles to enzymes and protein-modifying reagents resulted in numerous binding differences between the intracellular organelles and microvillus plasma membranes. Covalent affinity labelling with [125I]EGF revealed two major proteins of 155 and 140(X10(3)) Mr in all the organelles. The 155 X 10(3) Mr protein was labelled predominantly in all organelles except rough endoplasmic reticulum, where both proteins were equally labelled. Addition of proteolytic inhibitors during isolation of organelles did not alter the pattern of [125I]EGF-labelled binding proteins found in the organelles. EGF also stimulated phosphorylation of the 155 and 140(X10(3)) Mr proteins in all the organelles. The 155 X 10(3) Mr protein was phosphorylated more than the 140 X 10(3) Mr protein in microvillus plasma membranes and smooth endoplasmic reticulum, whereas the 140 X 10(3) Mr protein was phosphorylated more than the 155 X 10(3) Mr protein in lysosomes and both proteins were equally phosphorylated in rough endoplasmic reticulum. Several organelles also contained minor [125I]EGF-binding proteins that did not show phosphorylation response and proteins that showed phosphorylation response but did not bind [125I]EGF. Thus, the present study demonstrates by a number of different criteria, that several intracellular organelles of term human placenta also contain EGF-binding and kinase activities.

Autoradiography↗

PubMed1986

Quantitative electron microscopic autoradiographic studies on internalization of 125I-labelled epidermal growth factor in term human placenta.

The electron microscopic autoradiographic studies described here revealed the presence of specific silver grains over nuclei, lysosomal vesicles, rough endoplasmic reticulum and Golgi apparatus after incubation of placental tissue for 2 h at 38 degrees C with 1 nM-[125I]EGF. Three-step mask analysis, which corrects for radiation spread, showed that the relative grain density was the highest in nuclei, followed by lysosomal vesicles, then Golgi and rough endoplasmic reticulum, equally. The nuclear grain density, however, was lower than that in microvillus plasma membranes. There were very few grains in basolateral plasma membranes, none in the basement membrane area and a considerable number in capillary endothelial cells. The present results demonstrating the association of internalized [125I]EGF with a variety of intracellular organelles raise the possibility of EGF acting on the intracellular sites in addition to cell surface sites.

Autoradiography↗

PubMed1985

Topography of human placental receptors for epidermal growth factor.

These studies were undertaken to determine whether term human placental microvillus plasma membranes, which are exposed to maternal blood, and basolateral plasma membranes, which are in close proximity to fetal blood capillaries, contain receptors for epidermal growth factor (EGF). These two highly purified membranes bound 125I-EGF with similar affinity (apparent dissociation constants, 0.07-0.12 nM, but the total number of available receptors was greater in microvillus (8.2 pmol/mg protein) compared to basolateral (4.9 pmol/mg protein) plasma membranes. Detailed characterization of 125I-EGF binding to these membranes revealed numerous similarities as well as differences. The two membranes contained two major (155 and 140 kDa) and at least three minor (115, 175, and 210 kDa) specific 125I-EGF binding proteins. The 115-kDa protein was only found in basolateral plasma membranes. The 155-kDa protein was predominantly labeled in microvillus, whereas the 140-kDa protein was labeled predominantly in basolateral plasma membranes. The addition of protease inhibitors did not alter the multiple 125I-EGF binding proteins pattern found in these membranes. EGF stimulated phosphorylation of 140- and 155-kDa proteins in both microvillus and basolateral plasma membranes. However, the 155-kDa protein was phosphorylated to a greater extent in microvillus, whereas both 140- and 155-kDa proteins were phosphorylated equally in basolateral plasma membranes. Light and electron microscope autoradiographic studies revealed that 125I-EGF preferentially associated with microvillus plasma membranes. The data demonstrates the presence of EGF receptors in outer cell membranes of syncytiotrophoblasts and suggests that maternal EGF may influence syncytiotrophoblast function by binding to receptors in microvillus plasma membranes, while fetal EGF may also influence syncytiotrophoblast function but via receptors in basolateral plasma membranes.

Cell Membrane↗

PubMed1985

Epidermal growth factor binding to human amnion, chorion, decidua, and placenta from mid- and term pregnancy: quantitative light microscopic autoradiographic studies.

All of the cell types, but not noncellular elements, found in amnion, chorion, decidua, and placenta of mid- and term pregnancy contained numerous silver grains after incubation with 1 nM [125I]epidermal growth factor ([125I]EGF). These grains completely disappeared when excess unlabeled EGF, but not unlabeled insulin, was added with [125I]EGF, suggesting the presence of specific EGF receptors. Light cells of amnion contained more EGF receptors than dark cells of amnion, and the number of light cells decreased from mid- to term pregnancy. Numerous syncytiotrophoblasts containing a greater number of receptors than darkly stained cells in connective tissue were found in chorion from midpregnancy. The chorionic syncytiotrophoblasts were considerably reduced at term. Dark cells of decidua contained more receptors than light cells of decidua, and these cell numbers did not change during pregnancy. Placental syncytiotrophoblasts contained the EGF receptors. At mid- and term pregnancy, placenta contained the highest number of EGF receptors, followed by chorion greater than decidua greater than amnion. The receptor number in all tissues was higher at mid-compared to term pregnancy. A decrease in number of cells as well as a decrease or fewer receptors per cell during pregnancy may explain the tissue and mid- vs. term pregnancy differences. The higher number of EGF receptors in amnion, chorion, decidua, and placenta at midpregnancy, at a time when the maternal and fetal blood EGF levels are at their peak, suggests that EGF may exert maximal biological effects on the feto-placental unit at midpregnancy.

Amnion↗

PubMed1984

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.

Animals↗

PubMed1984

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.

Animals↗

PubMed1984

A quantitative electron microscope autoradiographic study on [3H]prostaglandin E1 and F2 alpha internalization in bovine luteal slices.

Very few silver grains were seen on the luteal cell surface and none intracellularly after incubation for 2 h at 4 degrees C with 10 nM [3H]prostaglandin (PG) E1 or [3H]PGF2 alpha. However, incubation at 22 degrees C or 38 degrees C for 2 h resulted in association of numerous grains on the luteal cell surface as well as in several intracellular organelles. Qualitatively, the grain distribution was similar at 22 degrees C and 38 degrees C, but quantitatively there were fewer grains at 22 degrees C than at 38 degrees C. In addition to luteal cells, the grains were also found on erythrocytes, platelets, fibroblasts and capillary endothelial cells in luteal tissue incubated with [3H]PGE1. Grain association with non-luteal cells was never seen with [3H]PGF2 alpha. Coincubation of [3H]PGE1 or [3H]PGF2 alpha with only corresponding excess unlabeled PGs resulted in complete disappearance of silver grains from all the subcellular organelles. In autoradiographs, grains were seen on plasma membranes, nuclei, lysosomes, mitochondria, rough and smooth endoplasmic reticulum and Golgi. Three-step mask analysis, which effectively corrects for radiation spread, revealed that the grains found on mitochondria and rough endoplasmic reticulum in the case of [3H]PGE1, and those found on mitochondria, rough and smooth endoplasmic reticulum and Golgi in the case of [3H]PGF2 alpha, were due to the radiation spread. For both [3H]PGE1 and [3H]PGF2 alpha the plasma membrane associated grains progressively decreased, while the 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 60 or 120 min. The optimized source density following 2 h of incubation at 38 degrees C with [3H]PGE1 was Golgi greater than plasma membranes greater than lysosomes = nuclei, and for [3H]PGF2 alpha, lysosomes greater than plasma membranes greater than nuclei. In summary, the present studies demonstrate for the first time that exogenously added [3H]PGE1 and [3H]PGF2 alpha internalize in bovine luteal cells in a ligand-specific, time- and temperature-dependent manner. The observations that the internalized [3H]PGE1 does not associate with rough endoplasmic reticulum and that [3H]PGF2 alpha does not associate with rough endoplasmic reticulum and Golgi, even though they contain the binding sites, suggest the presence of mechanism(s) to direct the internalized [3H]PGs to only certain intracellular organelles of luteal cells.

Alprostadil↗