Biomedical subjects

Y D Li

Publications and source records attributed to Y D Li.

At least 19 recordsLinked to original sources

PubMed2006

Genomic instability in phenotypically normal regenerants of medicinal plant Codonopsis lanceolata Benth. et Hook. f., as revealed by ISSR and RAPD markers.

Codonopsis lanceolata Benth. et Hook. f., commonly known as bonnet bellflower, is a high-valued herb medicine and vegetable. In this study, a large number of plants were regenerated via organogenesis from immature seed-derived calli in C. lanceolata by a simple and efficient method. Compared with the mother donor plant, the regenerated plants did not exhibit visible phenotypic variations in six major morphological traits examined at the stage of one-season-maturity under field conditions. To gain insight into the genomic stability of these regenerated plants, 63 individuals were randomly tagged among a population of more than 2,000 regenerants, and were compared with the single mother donor plant by two molecular markers, the inter-simple sequence repeats (ISSR) and randomly amplified polymorphic DNA (RAPD). Apparent genomic variation was detected in the 63 regenerants, whereas preexisting heterozygosiy in the donor plant was deemed minimal by testing 30 seedlings germinated from selfed seeds of the same donor plant. The percentages of polymorphic bands (PPB) in the ISSR and RAPD analysis were respectively 15.7 and 24.9% for the 63 regenerated plants. Cluster analysis indicates that the genetic similarity values calculated on the basis of RAPD and ISSR data among the 64 plants (63 regenerated and one donor) were respectively 0.894 and 0.933, which allow classification of the plants into distinct groups. Nineteen randomly isolated bands underlying the changed RAPD or ISSR patterns were sequenced, and three of them showed significant homology to known-function genes. Detailed pairwise sequence comparison at one locus between the donor plant and a regenerant revealed that insertion of two short (24 and 19 bp) stretches of nucleotides in the regenerated plant relative to the donor plant occurred in an apparently stochastic manner.

Base Sequence↗

PubMed2005

Microencapsulating hepatocytes.

BACKGROUND: Because standardization of the cell microencapsulation procedure has not yet been achieved, we performed hepatocyte microencapsulation using alginate (ALG)-poly-l-lysine (PLL)-ALG (APA) polymer. METHODS: Hepatocytes were microencapsulated using a binozzle air-jet droplet generator. Our study aims were to: (1) clarify how ALG concentration affects the quality of ALG beads; (2) determine how the PLL concentration affects the quality of microcapsules (MCs); (3) ascertain the influence of liquefaction time by sodium citrate (SC) on the quality of the MCs; (4) and clarify how temperature and solution pH, respectively, affect the viability of the hepatocytes inside the MCs. RESULTS: The concentration of ALG must be > or = 3% (w/v) to generate droplets with satisfactory homogeneity in size and roundness (P < .01). The total quantity of PLL molecules is the essential component for MCs (P < .01). As our results show, the numeric ratio of PLL (milligrams) to MCs (milliliters) is roughly 25:1. SC incubation for 8 minutes resulted in the proper thickness of the MC wall; however, the time varied according to the size of the MCs (P < .05). Temperature and pH, although both difficult to control, exerted great influences on cell viability: 4 degrees C and pH 7.2 were found to be optimal by this study (P < .05). CONCLUSIONS: Concentrations of ALG and PLL exerted decisive effects on the quality and strength of MCs. Higher concentrations were suggested. Because temperature and pH greatly affected cell viability, they must be properly monitored.

Alginates↗

PubMed2000

Synthesis of SnSe in various alkaline media under mild conditions.

The synthesis of SnSe was systematically investigated in various alkaline media and at various temperatures with SnCl2.2H2O and selenium as source materials. The basicity of the alkaline media and the reaction temperature are two key factors considered in our process. The synthesis of SnSe in sodium hydroxide solution and aqueous ammonia is limited to a narrow temperature range, while the synthesis in hydrazine hydrate and ethylenediamine proceeds over a wider range. The final products were characterized by X-ray diffraction pattern (XRD), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM). TEM results showed a variation of crystal morphology of SnSe obtained in different media. Two simple chemical mechanisms for the formation of SnSe are presented.

Journal Article↗

PubMed1999

Increased expression of calreticulin is linked to ANG IV-mediated activation of lung endothelial NOS.

This study demonstrates that ANG IV-induced activation of lung endothelial cell nitric oxide synthase (ecNOS) is mediated through mobilization of Ca(2+) concentration and by increased expression and release of the Ca(2+) binding protein calreticulin in pulmonary artery endothelial cells (PAEC). In Ca(2+)-free medium and in the presence of the ANG II AT(1) and AT(2) receptor antagonists losartan and PD-123319 (1 microM each), respectively, ANG IV (5, 50, and 500 nM) significantly increased intracellular Ca(2+) release in PAEC (P < 0.05 for all concentrations). In contrast, ANG IV-mediated activation of ecNOS was abolished by the intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM. ANG IV stimulation resulted in significantly increased expression of calreticulin in cells as well as release of calreticulin into the medium of cells as early as 2 h after ANG IV stimulation (P < 0.05). Catalytic activity of purified ecNOS in the absence of calmodulin was increased in a concentration-dependent fashion by calreticulin. Immunocoprecipitation studies revealed that ecNOS and calreticulin were coprecipitated in ANG IV-stimulated PAEC. These results demonstrate that ANG IV-mediated activation of ecNOS is regulated by intracellular Ca(2+) mobilization and by increased expression of calreticulin, which appears to involve interaction of ecNOS and calreticulin proteins in PAEC.

Angiotensin II↗

PubMed1998

Thioredoxin overexpression prevents NO-induced reduction of NO synthase activity in lung endothelial cells.

We recently reported that nitric oxide (NO) induces posttranscriptional modulation of lung endothelial cell NO synthase (ecNOS) that results in loss of activity. The loss of activity can be reversed by the redox regulatory proteins thioredoxin (Thx)/thioredoxin reductase (Thx-R). The present study was designed to examine whether diminished expression of endogenous Thx and Thx-R may account for regulation of ecNOS activity in NO-exposed cells and whether overexpression of Thx can prevent NO-induced reduction of ecNOS activity in cultured porcine pulmonary artery endothelial cells (PAEC). Exposure to 8.5 ppm NO gas for 24 h resulted in an 80% decrease of Thx and a 27% decrease of Thx-R mRNA expression. Similarly, NO exposure caused 30 and 50% reductions in Thx and Thx-R protein mass, respectively. This NO-induced decrease in the expression of Thx-R mRNA and protein was accompanied by a significant (P < 0.05) decrease in the catalytic activity of Thx-R but not of glutaredoxin or the cellular levels of reduced glutathione and oxidized glutathione. Overexpression of Thx gene in PAEC was achieved by transient transfection of these cells with pcDNA 3.1 vector inserted in sense or antisense (native) orientation in a human Thx cDNA. Thx mRNA and protein contents in transfected cells were four- and threefold higher, respectively, than those in native PAEC. Exposure of native cells to 10 microM NO solution for 30 min resulted in a significant (P < 0.01) loss of ecNOS activity, whereas ecNOS activity was comparable in Thx-overexpressed cells with or without NO exposure. These results demonstrate that NO exposure results in diminished expression of Thx and Thx-R in PAEC. Endogenous levels of Thx are critical to restoring the NO-induced loss of ecNOS activity because overexpression of Thx prevented the NO-induced loss of ecNOS catalytic activity. These results also demonstrate that NO modulation of ecNOS and Thx proteins is regulated by a physiologically relevant redox mechanism.

Animals↗

PubMed1998

Angiotensin IV receptor-mediated activation of lung endothelial NOS is associated with vasorelaxation.

The hexapeptide angiotensin (ANG) IV, a metabolic product of ANG II, has been reported to play a functional role in the regulation of blood flow in extrapulmonary tissues. Here, we demonstrate that ANG IV-specific (AT4) receptors are present in porcine pulmonary arterial endothelial cells (PAECs) and that the binding of ANG IV to AT4 receptors can be blocked by its antagonist divalinal ANG IV but not by the ANG II-, AT1-, and AT2-receptor blockers [Sar1,Ile8]ANG II, losartan, and PD-123177, respectively. ANG IV significantly increased endothelial cell constitutive nitric oxide synthase (ecNOS) activity (P < 0.05) as well as cellular cGMP content (P < 0. 001). Western blot analysis revealed that ecNOS protein expression was comparable in control and ANG IV-stimulated cells. Divalinal ANG IV but not [Sar1,Ile8]ANG II, losartan, or PD-123177 inhibited the ANG II- and ANG IV-stimulated increases in ecNOS activity and cGMP content in PAECs. Incubation in the presence of N-nitro-L-arginine methyl ester (L-NAME) or methylene blue but not of indomethacin significantly diminished ANG IV-stimulated as well as basal levels of cGMP (P < 0.001). Similarly, in situ studies with precontracted porcine pulmonary arterial rings showed that ANG IV caused an endothelium-dependent relaxation that was blocked by L-NAME or methylene blue. Collectively, these results demonstrate that ANG IV binds to AT4 receptors, activates ecNOS by posttranscriptional modulation, stimulates cGMP accumulation in PAECs, and causes pulmonary arterial vasodilation, suggesting that ANG IV plays a role in the regulation of blood flow in the pulmonary circulation.

Aminopeptidases↗

PubMed1997

Overexpression of plasma membrane annexin II in NO2-exposed pulmonary artery endothelial cells.

Because exposure to nitrogen dioxide (NO2) alters plasma membrane structure and function in pulmonary artery endothelial cells (PAEC), we examined whether NO2 exposure is associated with upregulation of plasma membrane-specific proteins in PAEC. Exposure to 5 ppm NO2 for 24 h had no significant effect on total protein synthesis. However, two-dimensional gel electrophoresis of isolated plasma membranes from [35S]-methionine pulse-labeled PAEC exposed to NO2 for 24 h demonstrated 3- to 9-fold increases in the synthesis of several proteins with molecular masses of 36, 39, and 40 kDa compared with controls. N-terminal amino acid sequencing and immunodetection analysis identified the 36kDa plasma membrane protein as annexin II (lipocortin II). Northern blotting analysis demonstrated that the mRNA expression for annexin II in NO2-exposed cells was also increased. These results suggest that exposure to NO2 results in induction of plasma membrane annexin II, an important multifunctional calcium- and phospholipid-binding protein in PAEC.

Amino Acid Sequence↗

PubMed1997

Proinflammatory cytokines downregulate gene expression and activity of constitutive nitric oxide synthase in porcine pulmonary artery endothelial cells.

We evaluated the effects of cytokines on the catalytic activity and expression of porcine pulmonary artery endothelial cell (PAEC) constitutive (eNOS) and inducible (iNOS) isoforms of nitric oxide synthase (NOS). Exposure of PAEC to the combination of IFN-gamma, TNF-alpha, and IL-1 beta did not alter iNOS activity in cytosolic and membrane fractions but significantly (p < 0.01) reduced eNOS activity in the membrane fraction, but not in the cytosolic fraction, after a 24-h exposure. The cytokine-induced loss of membrane fraction eNOS activity was associated with significant reductions of eNOS mRNA and protein content (p < 0.01 for both). Treatment with the protein synthesis inhibitor, cycloheximide, but not the transcriptional inhibitor actinomycin D prevented cytokine-induced reduction of eNOS mRNA expression. These results suggest that cytokine-induced loss of catalytic activity of eNOS is associated with a reduction in eNOS mRNA and protein mass and that cytokines alter eNOS mRNA stability. Inhibition of protein synthesis prevented reduction of eNOS mRNA by cytokines, suggesting that the mechanism by which cytokines alter eNOS mRNA stability involves protein synthesis.

Animals↗

PubMed1996

Reductase domain cysteines 1048 and 1114 are critical for catalytic activity of human endothelial cell nitric oxide synthase as probed by site-directed mutagenesis.

We examined whether highly conserved cysteine residues in the reductase domain of the constitutive isoform of nitric oxide synthase in human endothelial cells (ecNOS) are crucial for catalytic activity of the enzyme. Substitution of alanine for cysteines 976 (Cys-976), 991 (Cys-991), 1048 (Cys-1048), or 1114 (Cys-1114), located in the reductase domain of human ecNOS, was achieved by oligonucleotide-directed mutagenesis and expression in COS-7 cells. The specific activity of ecNOS was > 7-fold increased in wild-type and in mutants Cys-976 and Cys-991, but not in mutants Cys-1048 and Cys-1114. However, Western blot analysis indicated that expression of ecNOS protein was comparable in wild-type and in all mutants. NADPH concentration-dependent L-citrulline formation and NADPH oxidation during L-arginine metabolism were reduced in mutants Cys-1048 and Cys-1114 compared to wild-type. Similarly, NADPH cytochrome c reductase activity was increased in a time-dependent fashion in wild-type but not in mutants Cys-1048 and Cys-1114. These results indicate that Cys-1048 and Cys-1114 residues in the NADPH binding site of the reductase domain are critical for human ecNOS activity. The lack of utilization of NADPH in L-arginine metabolism and in cytochrome c reduction suggests that these active site cysteine residues may be responsible for binding of NADPH and/or for electron transfer in human ecNOS.

Animals↗

PubMed1996

NO2-induced expression of specific protein kinase C isoforms and generation of phosphatidylcholine-derived diacylglycerol in cultured pulmonary artery endothelial cells.

The present study examines whether nitrogen dioxide (NO2)-induced activation of protein kinase C (PKC) is associated with increased expression of specific PKC isoforms and/or with enhanced generation of phosphatidylcholine(PC)-derived diacylglycerol (DAG) in pulmonary artery endothelial cells (PAEC). Western blot analysis revealed that exposure to 5 ppm NO2 resulted in increased expression of PKC alpha and epsilon isoforms in both cytosol and membrane fractions in a time-dependent fashion compared with controls. A time-dependent elevated expression of PKC isoform beta was observed in the cytosol fraction only of N02-exposed cells. PKC isoform gamma was not detectable in either the cytosolic or membrane fractions from control or N02-exposed cells. Scatchard analysis of [3h]phorbol 12,13-dibutyrate (PDBu) binding showed that exposure to N02 for 24 h increased the maximal number of binding sites (Bmax) from 15.2 +/- 2.3 pmol/mg (control) to 42.3 +/- 5.3 pmol/mg (p < 0.01, n = 4) (NO2-exposed). Exposure to NO2 significantly increased PC specific-phospholipase C and phospholipase D activities in the plasma membrane of PAEC (p < 0.05 and p < 0.001, respectively). When [3H]-myristic acid-labeled cells were exposed to NO2, significantly increased radioactivity was associated with cellular DAG. These results show for the first time that exposure of PAEC to NO2 results in elevated expression of specific PKC isoforms and in enhanced generation of cellular DAG, and the latter appears to arise largely from the hydrolysis of plasma membrane PC.

Animals↗

PubMed1996

Nitrogen dioxide-induced expression of a 78 kDa protein in pulmonary artery endothelial cells.

Exposure to nitrogen dioxide (NO2) activates signal transduction in cultured pulmonary artery endothelial cells (PAEC). We examined whether NO2-induced activation of signal transduction results in increased expression of proteins in PAEC. Exposure to 5 ppm NO2 for 4, 12, and 24 h had no significant effect on total protein synthesis. However, two-dimensional gel electrophoresis of [35S]-methionine-labeled PAEC exposed to NO2 for 24 h, but not 4 and 12 h, demonstrated increased synthesis of several proteins including a two- to five-fold increase of some proteins with molecular masses of 47, 64, 78, and 105 kDa compared to controls. N-terminal amino acid sequencing and immunodetection analysis identified the 78 kDa protein as 78 kDa glucose-regulated protein (GRP-78). Induction of GRP-78 by NO2 exposure was regulated at the transcriptional level, and the induction required de novo protein synthesis. Exposure to NO2 for 24 h also significantly (p < .05) decreased glycosylation of proteins in PAEC. Exposure of cell monolayers to tunicamycin, an inhibitor of protein glycosylation, mimicked the effect of NO2 exposure on expression of GRP-78. Increased expression of GRP-78 was also detected when cell monolayers were exposed to the calcium ionophore A 23187, to 2-deoxyglucose, or to glucose-free medium, which are also known to cause perturbations in protein glycosylation. These results demonstrate that exposure to NO2 increases expression of a number of proteins including GRP-78 in PAEC. Increased expression of GRP-78 in NO2-exposed cells appears to be associated with inhibition of glycosylation or through coordinated alterations in metabolic events that lead to inhibition of protein glycosylation.

Amino Acid Sequence↗

PubMed1996

Balancing cost and precision in exposure assessment studies.

Because of the cost involved both for personnel and laboratory analyses, it is incumbent that industrial hygiene (IH) sampling plans be both precise and cost effective. The purpose of this paper is to describe a method of balancing two opposing objectives, increasing precision and decreasing the cost by manipulating the number and nature of IH sample collections. Data from a pilot study were used to obtain an optimum sampling scheme for exposure assessment. The design that obtains the highest precision while controlling costs serves as the model of choice. An approach is illustrated with data from an ongoing study examining health effects of workers exposed to solvents. It is shown that there is a large variation in precision for identical IH measurements, depending on the efficiency of the sampling schedule.

Aircraft↗

PubMed1994

Nitrogen dioxide-induced phosphatidylserine biosynthesis and subcellular translocation in cultured pulmonary artery endothelial cells.

Exposure to nitrogen dioxide (NO2) increases phosphatidylserine (PS) content in the plasma membranes of pulmonary artery endothelial cells (PAEC). We examined whether the increased PS content is associated with increased uptake of L-serine and/or biosynthesis of PS. Exposure to 5 ppm NO2 increased uptake and incorporation of exogenous L-[14C]serine into whole cells, total cellular lipids, phospholipids, and phospholipid subclasses compared to control. Incorporation of L-[14C]serine into the total lipid extracts from isolated plasma membranes, mitochondria, and microsomes from NO2-exposed cells was increased by 45, 32, and 31%, respectively (p < 0.05 for all membranes). Increased incorporation of L-[14C]serine into the total phospholipids of plasma membranes, mitochondria, and microsomes of NO2-exposed cells was increased by 31, 48, and 33%, respectively (p < 0.05 for all membranes). Incorporation of L-[14C]serine into the PS of plasma membranes and microsomes from NO2-exposed cells was increased by 63 and 89%, respectively (p < 0.05 for both membranes). The incorporation of radioactivity from L-[14C]serine into the phosphatidylethanolamine and phosphatidylcholine contents of plasma membranes, mitochondria, and microsomes from NO2-exposed cells was also observed. Exposure of PAEC to NO2 resulted in a significant (p < 0.01) increase in the activity of PS synthase, the serine base-exchange enzyme located in the microsomes of these cells. When L-[14C]serine-prelabeled microsomes were incubated with unlabeled mitochondria from control and NO2-exposed cells, transfer of PS-derived radioactivity from microsomes to mitochondrial phospholipids was observed. These results demonstrate that exposure to NO2 increases uptake and incorporation of exogenous serine as well as intracellular biosynthesis of PS, resulting in increases in the PS content of PAEC and their plasma membranes.

Analysis of Variance↗

PubMed1994

[Effects of rhizoma zedoariae on nickel sulfide induced unscheduled DNA synthesis of human lymphocytes].

The study was designed to investigate the toxic effects of Rhizoma Zedoariae (RZ) and nickel sulfide, and the effect of RZ on nickel sulfide induced unscheduled DNA synthesis (UDS) of human lymphocytes using an UDS assay of human lymphocytes. The results showed that TZ did not induce UDS, it could inhibit 3H-TdR incorporation with intracellular DNA when its' dose was 1 g/ml, that nickel sulfide and ultraviolet could largely induce UDS, that might be inhibited by RZ with a dose dependent relationship. These suggested that nickel sulfide induced damage of DNA might be inhibited by RZ, RZ was not mutagenic and DNA synthesis might be inhibited when the RZ dose amounted to 1 g/ml.

DNA↗

PubMed1994

[Pharmacological actions of hyphae body of Auricularia auricula (L. ex Hook) Underw and its alcoholic extract].

The percent peripheral blood T lymphocytes were elevated and HC50 reduction induced by cyclophosphamide was recovered after the hyphae body of Auricularia auricula had been ip administered in mice. The action of blood platelet agglutination in rats induced by ADP was inhibited and the time of erythrocytic electrophoresis in mice was shortened after the alcoholic extract had been ig administered.

Animals↗

PubMed1993

Preferential rearrangements of the V gamma I subgroup of the gamma-chain of the T-cell antigen receptor to J gamma 2C gamma 2 gene segments in peripheral blood lymphocyte transcripts from normal donors.

To investigate whether there are preferential VJC gene rearrangements of the gamma-chain of the human T-cell antigen receptor (TCR), we amplified and sequenced gamma-chain TCR transcripts from peripheral blood lymphocytes from adult normal donors. cDNA was synthesized from total RNA and amplified by the polymerase chain reaction (PCR) using 5' primers specific for either the V gamma I or the V gamma II subgroups of the gamma-chain of the TCR. The amplified cDNAs were then cloned and sequenced. The majority (approximately 83%) of the cDNAs employing V-I subgroup gene segments rearranged to J gamma 2 (J gamma 2.1 or J gamma 2.3) C gamma 2 gene segments. This was in contrast to the predominant rearrangement of the V gamma II subgroup (V gamma 9) to J gamma 1.2C gamma 1. The remaining 13% of the cDNAs employing V gamma I subgroup gene segments rearranged to J gamma 1.1C gamma 1 or J gamma 1.3C gamma 1. There was significant N diversity as well as imprecise joining at the VJ junction. gamma delta TCR utilizing the C gamma 1 gene segment are disulfide-linked, whereas those utilizing the C gamma 2 gene segment are non-disulfide-linked. These results demonstrate that peripheral blood gamma-chain transcripts exhibit preferential rearrangements of V gamma I subgroup gene segments to J gamma 2(2.1,2.3)C gamma 2 gene segments. By contrast, V gamma II subgroup (V gamma 9) transcripts exhibit rearrangements to J gamma 1.2C gamma 1.

Amino Acid Sequence↗

PubMed1993

Androgens augment vasoactive intestinal peptide- and growth hormone-releasing hormone-stimulated progestin production by rat granulosa cells.

Vasoactive intestinal peptide (VIP) has been shown to stimulate steroid production by cultured rat granulosa cells independently of FSH. In the present study, we have examined the modulatory effects of various steroids on this response. Rat granulosa cells cultured for 2 days with only VIP showed small but significant increases in progesterone and 20 alpha-dihydroprogesterone (20 alpha-OH-P) production. Concomitant treatment with either a synthetic estrogen (diethylstilbestrol), a synthetic progestin (R5020), or cortisol did not augment VIP-stimulated progesterone production; however, the latter two steroids slightly, but significantly, augmented VIP-stimulated 20 alpha-OH-P production. In contrast, concomitant treatment with a synthetic androgen (R1881) dramatically augmented both VIP-stimulated progesterone and 20 alpha-OH-P production. These effects were dose dependent for both VIP and R1881 and could be blocked by the androgen antagonist cyproterone acetate. Time course studies revealed that progesterone content of the culture media rapidly increased over the first 24 h of culture then remained fairly constant for the next 48 h; 20 alpha-OH-P content, on the other hand, was low for the first 12 h of culture and steadily increased thereafter. Dose-response analysis for R1881 revealed an ED50 of approximately 2 x 10(-8) M for the synthetic androgen, and comparison with other naturally occurring androgens provided the rank order of potency R1881 > androstenedione > testosterone = dihydrotestosterone. Additional studies with another member of the VIP peptide family, GH-releasing hormone, showed dose-dependent stimulation of progesterone and 20 alpha-OH-P production by this peptide. These effects were also augmented by R1881 but not by diethylstilbestrol, R5020, or cortisol. These studies demonstrate that androgens, but not estrogens, progestins, or glucocorticoids, augment VIP- and GH-releasing hormone-stimulated progestin production by cultured rat granulosa cells.

20-alpha-Dihydroprogesterone↗

PubMed1991

Transferrin inhibits aromatase activity of rat granulosa cells in vitro.

The effect of transferrin on basal and FSH-stimulated aromatase activity of granulosa cells from immature female rats treated with diethylstilboestrol (DES) was examined in vitro by a radiometric method. The basal activity of the enzyme was very low after 3 days of incubation. Treatment with FSH (20 ng/ml) resulted in a 9.6-fold increase in activity, whereas coincubation with increasing doses of transferrin (3-300 micrograms/ml) produced a dose-dependent inhibition of FSH-stimulated aromatase activity with a projected minimal effective dose of less than 2 micrograms/ml. A time-course study showed that the inhibitory effect of transferrin on aromatase activity has become significant at 48 h of incubation. The inhibitory action of transferrin on the enzyme complex was further confirmed by showing that the FSH dose-response curve was significantly suppressed by concomitant treatment with 100 micrograms transferrin/ml with a maximum suppression of 54.1% at a dose of 30 ng FSH/ml. The possibility that transferrin may act through a non-specific inhibitory effect seems unlikely, as no changes in cell number and DNA content per well were observed. In fact, protein synthesis was enhanced after treatment with transferrin. Aromatase activity, stimulated by several promoters of cyclic AMP (cAMP), such as prostaglandin E2 (PGE2), forskolin and 8-bromo-cAMP, was significantly suppressed by 100 micrograms transferrin/ml (36.6, 47.4 and 23.4% inhibition respectively), suggesting that the effect of transferrin on FSH action may involve a site(s) distal to cAMP generation. These findings indicated that transferrin, present in follicular fluid, may play an important role in the regulation of granulosa cell differentiation.

Animals↗