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PubMed2004

Lunasin concentration in different soybean genotypes, commercial soy protein, and isoflavone products.

Lunasin is a unique and novel cancer preventive peptide originally isolated from soy. Information on lunasin concentration of soybean cultivars and commercial soy proteins would be useful in developing lunasin-enriched cultivars and soy products. We report the development of an enzyme-linked immunosorbent assay (ELISA) method to identify lunasin and quantify the variations in concentration in 144 selected, diverse soybean accessions from the U.S. Department of Agriculture Soybean Germplasm Collection, several commercially available soy protein fractions and isoflavone-enriched products. With synthetic lunasin and monoclonal antibody, ELISA shows a linear concentration range of 24-72 ng/mL, good reproducibility, a detection limit of 8 ng/mL, and a recovery of 90% on spiked soy samples. Lunasin concentrations in the tested materials range from 0.10 to 1.33 g/100 g flour. Differences that exceeded 100% have been observed among accessions of similar maturity that were grown in the same environment, indicating that genetic differences in soybeans exist for lunasin. The mean of 23 major ancestral lines of U.S. cultivars is similar to the mean of 16 modern cultivars selected to represent the current diversity of the crop, but the highest values were found within the ancestral and exotic accessions. Soy protein concentrate, isolate, and hydrolyzate contain 2.81 +/- 0.30, 3.75 +/- 0.43, and 4.43 +/- 0.59 g lunasin/100 g flour, respectively, while soy flour and soy flakes contain 1.24 +/- 0.22 g lunasin/100 g flour. Isoflavone-enriched products contain very little or no lunasin. The relative mass (M(r)) of lunasin in the samples is 5.45 +/- 0.25 kDa. The wide range of lunasin concentrations within the Glycine max species indicates that the levels of this important bioactive peptide can be genetically manipulated. Furthermore, soy isolates and hydrolyzed soy proteins contain the highest concentrations of lunasin.

Antibodies, Monoclonal↗

PubMed1982

The interaction of glucagon, gastric inhibitory peptide and somatostatin with cyclic AMP production systems present in rat gastric glands.

The effects of glucagon, gastric inhibitory peptide (GIP) and somatostatin on the generation of cyclic AMP have been studied under basal and histamine- or secretin-stimulated conditions in tubular gastric glands isolated by means of EDTA from the rat fundus and antrum. Four types of cell could be identified by electron microscopy; namely, parietal, mucous, peptic and some endocrine cells with a good morphological preservation of the cellular topography as seen in the intact mucosa. Immunoreactive somatostatin was found in antral glands (210 +/- 16 ng/g cell, wet wt., n = 9) as well as in fundic glands, but in smaller concentration (50 +/- 8 ng/g cell, wet wt., n = 9). (1) In rat fundic glands, glucagon, in supraphysiologic doses (3 . 10(-9) -5 . 10(-7) M), raised cyclic AMP levels 46 times above the basal. At maximally effective doses, combination of glucagon plus histamine was not additive whereas glucagon and secretin stimulations resulted in an additive response. Somatostatin (10(-10) -10(-7) M) inhibited both glucagon- and histamine-induced cyclic AMP production, whereas cimetidine specifically blocked the histaminergic stimulation. (2) In the same conditions, 10(-6)M glucagon produced a marginal effect (4-fold increase) in rat antrum, whereas GIP (10(-9) -10(-6)M) was unable to induce a significant rise of cyclic AMP production in either fundic or antral glands, or to prevent cyclic AMP production stimulated by histamine. (3) The present data do not support the view that circulating glucagon or GIP may regulate gastric secretion directly by a cyclic AMP-dependent mechanism in rat gastric glands and raise the possibility that gastric somatostatin may be the final mediator of the inhibitory actions of these hormones on acid secretion. (4) It is proposed that pancreatic glucagon acts through a receptor-cyclic AMP system which is specific for the bioactive peptide enteroglucagon ('oxyntomodulin'), probably in rat parietal cells.

1-Methyl-3-isobutylxanthine↗

PubMed1997

Expression and localization of aminopeptidase A, aminopeptidase N, and dipeptidyl peptidase IV in benign and malignant human prostate tissue.

BACKGROUND: Cell-surface peptidases are ectoenzymes which regulate the access of bioactive peptides to their receptors on cell membranes. Abnormalities in their expression and function result in altered peptide activity which contribute to neoplastic transformation and/or progression. METHODS: Expression of aminopeptidase A (APA), aminopeptidase N (APN, CD13), and dipeptidyl peptidase IV (DPP IV, CD26) was immunohistochemically examined in 20 benign and 33 malignant prostate tissues (19 primaries and 14 metastases). RESULTS: Benign prostatic stroma exhibited no APA, APN, or DPP IV immunoreactivity. Stromal cells surrounding prostatic carcinoma cells demonstrated increased APA expression in 24/33 (73%) of tumors. Benign prostatic epithelial cells strongly expressed APN and DPP IV but not APA. In contrast, APN was expressed in > 80% of tumor cells in 5/33 (15%) of specimens, heterogeneously expressed (20-80% of cells positive) in 4/33 (12%) of specimens, and minimally expressed or absent in 24/33 (73%) of tumor specimens, with a similar pattern of expression in primary and metastatic tumors. DPP IV was expressed by > 80% of tumor cells in 18/19 (95%) of primary prostate cancer specimens, but in only 7/14 (50%) of metastases. CONCLUSIONS: These data show that cell-surface peptidases are differentially expressed by normal prostatic stromal and epithelial cells, with increased expression of APA in the stroma surrounding prostate cancer cells, absent APN expression in most tumor cells, and a decreased frequency of DPP IV expression in metastatic tumors. Further studies will elucidate the biological effects of the presence or loss of cell-surface peptidases in the benign and malignant prostate.

Aged↗

PubMed2001

Ectopeptidases in pathophysiology.

Ectopeptidases are transmembrane proteins present in a wide variety of tissues and cell types. Dysregulated expression of certain ectopeptidases in human malignancies suggests their value as clinical markers. Ectopeptidase interaction with agonistic antibodies or their inhibitors has revealed that these ectoenzymes are able to modulate bioactive peptide responses and to influence growth, apoptosis and differentiation, as well as adhesion and motility, all functions involved in normal and tumoral processes. There is evidence that ectopeptidase-mediated signal transduction frequently involves tyrosine phosphorylation. Combined analyses of gene organization and regulation of ectopeptidases by various physiological factors have provided insights into their structure-function relationships. Understanding the roles of ectopeptidases in pathophysiology may have implications in considering them as therapeutic targets.

Cell Transformation, Neoplastic↗

PubMed1993

Role of apical ion channels in sour taste transduction.

Sour taste perception depends primarily on the concentration of H+ in the taste stimulus. Acid stimuli elicit concentration-dependent action potentials in taste cells. Recent patch-clamp studies suggest that protons depolarize taste cells by direct interaction with apically located ion channels. In Necturus maculosus, the voltage-dependent K+ conductance is restricted to the apical membrane of taste cells. The current flows through a variety of K+ channels with unitary conductances ranging from 30 to 175 pS, all of which are blocked directly by citric acid applied to outside-out or perfused cell-attached patches. In contrast, hamster fungiform taste cells appear to utilize the amiloride-sensitive Na+ channel for acid transduction. Amiloride completely inhibits H+ currents elicited by acid stimuli in isolated taste cells, with an inhibition constant similar to that for amiloride-sensitive Na+ currents (Ki = 0.2 microM). Treatment of isolated taste cells with the bioactive peptide arginine-vasopressin results in similar increases in both the amiloride-sensitive Na+ and H+ currents; the effect is mimicked by 8-bromocyclic AMP. These results suggest that H+ can permeate amiloride-sensitive Na+ channels in hamster fungiform taste cells, contributing to the transduction of sour stimuli.

Animals↗

PubMed2004

ROS production and Glut1 activity in two human megakaryocytic cell lines.

Reactive oxygen species (ROS) has been increasingly recognised as intracellular messengers in signal transduction following receptor activation by a variety of bioactive peptides including growth factors, cytokines and hormones. In this study ROS production and glucose transport activity were evaluated in the growth factor dependent M07e cells and in B1647 cells, not requiring additional hematopoietic cytokines for growth: the aim was to investigate whether ROS could be involved in the regulation of Glut1-mediated glucose uptake in both cell lines. The effect of the synthetic superoxide and hydrogen peroxide scavenger EUK-134 on DOG uptake activity and intracellular ROS formation supports the concept of reactive oxygen species as signalling molecules. In order to investigate ROS generation sources, diphenyleneiodonium, an inhibitor of flavoprotein centres and apocynin, an inhibitor of NAD(P)H oxidase, were used: they inhibit both ROS production and glucose uptake activation. All these data support the hypothesis that ROS can contribute to the regulation of glucose transport, not only in M07e cells but also in B1647 cells; we could speculate that one possible source of ROS, linked somehow with Glut1 activity, can be a NAD(P)H oxidase similar to that one present in phagocytic cells.

Biological Transport↗

PubMedDate not supplied

EP24.15 interacts with the angiotensin II type I receptor and bradykinin B2 receptor.

The carboxyl-terminal cytoplasmic domain of the angiotensin II type 1 receptor (AT1) is known to interact with several classes of intracellular proteins that may modulate receptor function. Employing yeast two-hybrid screening of a human embryonic kidney cDNA library with the carboxyl-terminal cytoplasmic domain of the AT1 receptor as a bait, we have isolated EP24.15 (EC 3.4.24.15, thimet oligopeptidase) as a potentially interacting protein. EP24.15 is widely distributed and is known to degrade bioactive peptides such as angiotensin I and II and bradykinin. In addition, EP24.15 was previously identified as a putative soluble angiotensin II binding protein. Two-hybrid screening also determined that EP24.15 can interact with the B2 bradykinin receptor. Transient expression of EP24.15 in a porcine kidney epithelial cell line stably expressing full length AT1 and full length B2 followed by affinity chromatography and co-immunoprecipitation confirmed EP24.15 association with both AT1 and B2 receptors. EP24.15 was also co-immunoprecipitated with AT1 and B2 in rat kidney brush border membranes (BBM) and basolateral membranes (BLM). Both AT1 and B2 undergo ligand-induced endocytosis. Analysis of endosomal fractions following immunoprecipitation with AT1 or B2 antibodies detected strong association of EP24.15 with the receptors in both light and heavy endosomal populations. Therefore, the present study indicates that EP24.15 associates with AT1 and B2 receptors both at the plasma membrane and after receptor internalization and suggests a possible mechanism for endosomal disposition of ligand that may facilitate receptor recycling.

Animals↗

PubMed2002

Distribution and synaptic connectivity of neuropeptide Y-immunoreactive amacrine cells in the rat retina.

Neuropeptide Y (NPY) is a potent bioactive peptide that is widely expressed in the nervous system, including the retina. Here we show that specific NPY immunoreactivity was localized to amacrine and displaced amacrine cells in the rat retina. Immunoreactive cells had a regular distribution across the retina and an overall cell density of 280 cells/mm(2) in the inner nuclear layer (INL) and 90 cells/mm(2) in the ganglion cell layer (GCL). In the INL, most immunoreactive cells were characterized by small cell bodies and fine processes that appeared to ramify primarily in stratum 1 of the inner plexiform layer (IPL). A few cells in the INL also ramified in stratum 3 of the IPL. In the GCL, small to medium immunoreactive cells appeared to ramify primarily in stratum 5 of the IPL. A few immunoreactive processes, originating from somata in the INL and processes in the IPL, ramified in the OPL. NPY-immunoreactive cells contained GABA immunoreactivity, and some amacrine cells also contained tyrosine hydroxylase immunoreactivity. NPY-immunostained processes were most frequently presynaptic to nonimmunostained amacrine and ganglion cell processes and postsynaptic to nonimmunostained amacrine cell processes and cone bipolar cell axonal terminals. These findings indicate that NPY immunoreactivity is present in two populations of amacrine cells, one located in the INL and the other in the GCL, and that these cells mainly form synaptic contacts with other amacrine cells. These observations suggest that NPY-immunoreactive cells participate in multiple circuits mediating visual information processing in the inner retina.

Amacrine Cells↗

PubMed1989

Vasopressin- and proctolin-like immunoreactive efferent neurons in blowfly abdominal ganglia: development and ultrastructure.

In the neural sheath of the fused thoracicoabdominal ganglia of the blowfly Calliphora erythrocephala, extensive neurohaemal areas can be seen in the electron microscope. A separate set of neurohaemal areas located in the sheath of the lateral abdominal nerve roots contain neural terminals of at least three morphological types. To determine which bioactive substances are stored and possibly released from the neurons supplying these neurohaemal areas, we applied a large number of antisera raised against different neuropeptides of invertebrate and mammalian type. Antisera to two types of neuropeptides react with neurons innervating the sheath of the abdominal nerve roots: antisera to lysine-vasopressin and proctolin. There are only 14-24 vasopressin-like immunoreactive (VPLI) neurons in the entire nervous system of Calliphora. These are all restricted to a bilateral cluster in the fused abdominal ganglia. From this cluster, the neurohaemal areas in abdominal nerve roots are supplied. Proctolin-like immunoreactivity (PLI) can be seen in a large number of neurons in the nervous system of blowflies. The supply of PLI terminals to the abdominal nerve roots is from 12 to 14 neurons in a bilateral cluster of abdominal PLI neurons. It is clear from light- and electron-microscopic immunocytochemistry that the two antisera label two separate populations of neurons that form overlapping terminals in the neural sheath. The immunoreactive terminals are located just below the permeable acellular basal lamina of the neural sheath. Hence, it is likely that at least two different bioactive peptides can be released neurohormonally into the circulation. An additional set of four efferent PLI neurons send axons into the medial abdominal nerve. These do not form neurohaemal terminals in the nerve root, but may innervate the hindgut. Also in the larval nervous system, VPLI and PLI neurons can be recognized. In the larva, the peptide-containing neurons are segmentally arranged. The 14 larval VPLI neurons supply segmental abdominal nerves with axons that run inside the nerves to their targets. During metamorphosis, the segmental nerves fuse and the VPLI axons invade the neural sheath where they arborize and form varicose terminals. About the same number of PLI neurons could be detected in the abdominal ganglia of larval and adult flies. Only for a set of four caudal PLI neurons could efferent axons be traced in the larva. These axons run inside the medial abdominal nerves. The same four PLI neurons, with the same axonal projections, can be recognized in the adults.

Animals↗

PubMed2004

Amino-terminal processing of MIP-1beta/CCL4 by CD26/dipeptidyl-peptidase IV.

CD26 is a membrane-bound ectopeptidase with dipeptidyl peptidase IV (DPPIV) activity that has diverse functional properties in T cell physiology and in regulation of bioactive peptides. We have previously reported that activated human peripheral lymphocytes (PBL) secrete an amino-terminal truncated form of macrophage inflammatory protein (MIP)-1beta/(3-69) with novel functional specificity for CCR1, 2, and 5. In this report, we show that the full length MIP-1beta is processed by CD26/DPPIV to the truncated form and that cleavage can be blocked by DPPIV inhibitory peptides derived from HIV Tat(1-9) or the thromboxane A2 receptor, TAX2-R(1-9). Addition of Tat(1-9) or TAX2-R(1-9) peptides to PBL cultures partially blocks endogenous MIP-1beta processing. The kinetics of conversion of MIP-1beta from intact to MIP-1beta(3-69) in activated PBLs correlates with cell surface expression of CD26. Our results suggest that NH2-terminal processing of MIP-1beta and possibly other chemokines may depend on the balance between CD26/DPPIV enzymatic activity and cellular and viral proteins that modulate enzyme function.

Chemokine CCL4↗

PubMed2002

Neurotrophins and their receptors in the primary olfactory neuraxis.

The primary olfactory pathway is an elegant and simple system in which to study neurogenesis and neuronal plasticity because of the simple fact that olfactory receptor neurons (ORNs) are continually generated throughout the adult lifetimes of vertebrates. Thus, neuronal birth, differentiation, survival, axon pathfinding, target recognition, synapse formation, and cell death are developmental events that can be examined in the mature olfactory epithelium (OE). Neurotrophins (nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3, and 4/5) are a family of bioactive peptides that exert their effects by interacting with high- and low-affinity receptors on the surfaces of responsive cells, and have been implicated in several stages of neuronal development throughout the central and peripheral nervous system (CNS and PNS). There has been significant interest within the olfactory community as to how these multifunctional peptides might regulate the cycle of degeneration and regeneration of olfactory receptor neurons. The focus of this review is to highlight what is known about the actions of neurotrophins in the primary olfactory pathway, and to pinpoint future directions that will enable us to further understand their role in olfactory receptor neuron development and turnover.

Animals↗

PubMed2003

Novel roles of neuropeptide processing enzymes: EC3.4.24.15 in the neurome.

Neuropeptide processing metalloenzymes, such as angiotensin converting enzyme, neprilysin, endothelin converting enzyme, neurolysin, and EC3.4.24.15 (EP24.15), are central to the formation and degradation of bioactive peptides. We present EP24.15 as a paradigm for novel functions ascribed to these enzymes in the neurome. Although the neurome typically encompasses proteomes of the brain and central nervous system, exciting new roles of these neuropeptidases have been demonstrated in other organ systems. We discuss the involvement of EP24.15 with clinical sequelae involving the use of gonadotropin-releasing hormone (GnRH; LHRH) analogs that act as enzyme inhibitors, in vascular physiology (blood pressure regulation), and in the hematologic system (immune surveillance). Hemodynamic forces, such as cyclic strain and shear stress, on vascular cells, induce an increase in EP24.15 transcription, suggesting that neuropeptidase-mediated hydrolysis of pressor/depressor peptides is likely regulated by changes in hemodynamic force and blood pressure. Lastly, EP24.15 regulates surface expression of major histocompatibility complex Class I proteins in vivo, suggesting that EP24.15 may play an important role in maintenance of immune privilege in sites of increased endogenous expression. In these extraneural systems, regulation of both neuropeptide and other peptide substrates by neuropeptidases indicates that the influence of these enzymes may be more global than was anticipated previously, and suggests that their attributed role as neuropeptidases underestimates their physiologic actions in the neural system.

Animals↗

PubMed1995

Serum fractions and related agonists with calcium-mobilizing activity in the bovine growth plate chondrocyte.

Longitudinal growth of bone involves a complex sequence of cellular events in the cartilaginous epiphysis. Whole blood serum has been shown previously to be a potent stimulus to the cells of the growth plate, as demonstrated by its ability to activate the inositol phosphate-calcium second messenger system, resulting in a rise in intracellular Ca2+. By manipulating the preparation of serum to functionally separate it into its constituent parts, we have shown that the processes of platelet lysis and activation of the clotting cascade are responsible for the generation of factors that stimulate this signaling mechanism in isolated bovine growth plate chondrocytes. Through a subsequent trial of bioactive agents generated in these processes, we identified and partially characterized several novel agonists of growth plate chondrocytes:adenosine triphosphate and adenosine diphosphate, the purine energy substrates, and bradykinin, the bioactive peptide generated in a side reaction of the clotting cascade, each induces a rise in intracellular Ca2+ via release from intracellular ion stores. Additionally, the three distinct isoforms of platelet-derived growth factor (AA, AB, and BB), also released on platelet lysis, were compared with respect to their ability to stimulate the inositol phosphate-calcium second messenger system in growth plate chondrocytes.

Adenine Nucleotides↗

PubMed2006

Aminopeptidase-N/CD13 (EC 3.4.11.2) inhibitors: chemistry, biological evaluations, and therapeutic prospects.

Aminopeptidase N (APN)/CD13 (EC 3.4.11.2) is a transmembrane protease present in a wide variety of human tissues and cell types (endothelial, epithelial, fibroblast, leukocyte). APN/CD13 expression is dysregulated in inflammatory diseases and in cancers (solid and hematologic tumors). APN/CD13 serves as a receptor for coronaviruses. Natural and synthetic inhibitors of APN activity have been characterized. These inhibitors have revealed that APN is able to modulate bioactive peptide responses (pain management, vasopressin release) and to influence immune functions and major biological events (cell proliferation, secretion, invasion, angiogenesis). Therefore, inhibition of APN/CD13 may lead to the development of anti-cancer and anti-inflammatory drugs. This review provides an update on the biological and pharmacological profiles of known natural and synthetic APN inhibitors. Current status on their potential use as therapeutic agents is discussed with regard to toxicity and specificity.

Animals↗

PubMed1992

The role of TGF-beta s in mammalian development and neoplasia.

To date, three mammalian TGF-beta isoforms have been identified, each encoded by different genetic loci. Through each is very similar in primary amino acid structure, there are clear differences both in the mature bioactive peptide region and in the latency-associated peptide, which could potentially confer differential biological specificity. As one route to investigate differential biological function in vivo we have used gene specific probes for in situ hybridization studies to examine the distribution of RNA transcripts during mammalian embryogenesis. Mouse embryos from 6 to 14.5 gestational age and human embryos from 32 to 57 days post-fertilization have been probed. A general conclusion from these studies is that each TGF-beta gene has a distinct, through overlapping, pattern of transcript distribution and that this pattern, in most cases, is conserved between mouse and man. We have focused on the biological function the TGF-betas play in certain epithelia and in cardiogenesis, which will be discussed in this presentation.

Animals↗

PubMed2006

Proopiomelanocortin gene expression and beta-endorphin localization in the pituitary, testis, and epididymis of stallion.

Proopiomelanocortin (POMC) is a precursor protein that contains the sequences of several bioactive peptides including adrenocorticotropin (ACTH), beta-endorphin (beta-EP), and melanocyte-stimulating-hormone (MSH). POMC is synthesized in the pituitary gland, brain, and many peripheral tissues. Immunoreactive POMC-derived peptides as well as POMC-like mRNA have been evidenced in several nonpituitary tissues, thus suggesting that POMC is actively synthesized by these tissues. The present study was aimed at evaluating if also in the case of stallion POMC-derived peptide, beta-EP, is produced locally in the testis, thus playing effects in a paracrine/autocrine fashion. To investigate this hypothesis the POMC gene expression was analyzed using 3' RACE-PCR and Northern Blot approaches in the testis and epididimys of stallion; moreover, immunocytochemical localization for beta-EP was also performed through confocal laser microscopy. The immunofluorescence results showed a positive beta-EP reaction not only in cellular nest of pituitary but also in the testis and genital tract of stallion, which function could be related with sperm mobility. Such role seem not to be no dependent on the peptide synthesized locally, because the molecular biology approach demonstrated the presence of POMC transcript in the pituitary only. In fact the Northern Blot analysis showed the presence of a single POMC transcript in the pituitary while no signal was detected in the testis and epididimys. The same results were obtained by applied 3' RACE-PCR analysis. In conclusion, opioid-derived peptide beta-EP is present in the genital tract of stallion, but is not locally produced as in other mammalian, and nonmammalian models; its possible biological function at testicular level could be linked to a long-loop feed-back mechanisms.

Animals↗

PubMed1995

Growth inhibition of human prostate tumor cells by an agonist of gonadotrophin-releasing hormone.

The effect of [D-Leu6,des-Gly-NH2(10),Proethylamide9]-GnRH, leuprolide, was determined for the human primary prostate tumor cell line ALVA-31 by in vitro mitogenic assays. Prostate tumor cell proliferation was inhibited up to 50% by leuprolide. Inhibition was not observed in parallel cultures treated with other low molecular weight bioactive peptides. The incorporation and metabolic reduction of testosterone was not affected by concentrations of leuprolide that were inhibitory in the mitogenic assay. Specific high-affinity binding of 125I-labeled leuprolide was also demonstrated on intact tumor cells with an estimated effective median dose (ED50) of < 1 x 10(-9)M. Inhibition of prostate tumor growth was further demonstrated in Balb/c athymic intact and castrate male mice bearing ALVA-31 tumor xenografts following chronic administration of leuprolide. These data clearly demonstrate that leuprolide can inhibit the growth of a human prostate carcinoma cell line. Studies conducted in castrate animals further suggest an alternative mechanism of growth inhibition that appears to be independent of the suppression of steroid hormone biosynthesis by LHRH analogues.

Animals↗

PubMed2006

Synthesis, liposomal formulation and thermal effects on phospholipid bilayers of leuprolide.

A novel liposomal formulation was developed for the encapsulation of the oligopeptide leuprolide (GlpHisTrpSerTyr-D-LeuLeuArgProNHEt), a potent analogue of gonadotropin releasing hormone used in the treatment of advanced prostate cancer, endometriosis and precocious puberty. Leuprolide was synthesized using solid phase methodology on a {3-[(ethyl-Fmoc-amino)-methyl]-1-indol-1-yl}-acetyl AM resin and Fmoc/tBu chemistry. The new liposomal formulation, called 'liposomes in liposomes' is composed of egg phosphatidylcholine:dipalmitoylphosphatidylglycerol in a molar ratio of 98.91:1.09 (internal liposomes) and egg phosphatidylcholine:dipalmitoylphosphatidylglycerol:cholesterol in a molar ratio of 68.71:0.76:30.53 (external liposomes). It offers high encapsulation efficiency (73.8% for leuprolide); it can provide new delivery characteristics and it may have possible advantages in future applications regarding the encapsulation and delivery of bioactive peptides to target tissues. Furthermore, the physicochemical characteristics (size distribution and zeta-potential) of the liposomal formulations and the thermal effects on leuprolide in model lipidic bilayers composed of dipalmitoylphosphatidylcholine were studied using differential scanning calorimetry. Finally, the dynamic effects of leuprolide in an egg phosphatidylcholine/cholesterol system were examined using solid state 13C MAS NMR spectroscopy.

Calorimetry, Differential Scanning↗