Robust anti-obesity and metabolic effects of a dual GLP-1/glucagon receptor peptide agonist in rodents and non-human primates.

AIMS: To characterize the pharmacology of MEDI0382, a peptide dual agonist of glucagon-like peptide-1 (GLP-1) and glucagon receptors. MATERIALS AND METHODS: MEDI0382 was evaluated in vitro for its ability to stimulate cAMP accumulation in cell lines expressing transfected recombinant or endogenous GLP-1 or glucagon receptors, to potentiate glucose-stimulated insulin secretion (GSIS) in pancreatic ß-cell lines and stimulate hepatic glucose output (HGO) by primary hepatocytes. The ability of MEDI0382 to reduce body weight and improve energy balance (i.e. food intake and energy expenditure), as well as control blood glucose, was evaluated in mouse models of obesity and healthy cynomolgus monkeys following single and repeated daily subcutaneous administration for up to 2 months. RESULTS: MEDI0382 potently activated rodent, cynomolgus and human GLP-1 and glucagon receptors and exhibited a fivefold bias for activation of GLP-1 receptor versus the glucagon receptor. MEDI0382 produced superior weight loss and comparable glucose lowering to the GLP-1 peptide analogue liraglutide when administered daily at comparable doses in DIO mice. The additional fat mass reduction elicited by MEDI0382 probably results from a glucagon receptor-mediated increase in energy expenditure, whereas food intake suppression results from activation of the GLP-1 receptor. Notably, the significant weight loss elicited by MEDI0382 in DIO mice was recapitulated in cynomolgus monkeys. CONCLUSIONS: Repeated administration of MEDI0382 elicits profound weight loss in DIO mice and non-human primates, produces robust glucose control and reduces hepatic fat content and fasting insulin and glucose levels. The balance of activities at the GLP-1 and glucagon receptors is considered to be optimal for achieving weight and glucose control in overweight or obese Type 2 diabetic patients.

Liver X receptor agonists ameliorate TNFalpha-induced insulin resistance in murine brown adipocytes by downregulating protein tyrosine phosphatase-1B gene expression.

AIMS/HYPOTHESIS: The nuclear receptors, including nuclear receptor subfamily 1, group H, member 3 (NR1HR, also known as liver X receptor [LXR]), are sensors of cholesterol metabolism and lipid biosynthesis that have recently been proposed as insulin sensitisers. TNFalpha has been described as a link between obesity and the development of insulin resistance, an important contributor to the pathogenesis of type 2 diabetes. Therefore, we decided to investigate the ability of NR1HR agonists to ameliorate TNFalpha-induced insulin resistance in brown adipocytes. METHODS: Primary brown adipocytes from rat fetuses, and from wild-type neonate mice and neonate mice deficient in the gene encoding protein tyrosine phosphatase-1B (Ptpn1, also known as Ptp1b) were cultured in the absence or presence of TNFalpha and different nuclear receptor agonists. Among them, the unrelated NR1HR ligands T0901317, GW3965 and (22R)-hydroxycholesterol were tested. After insulin stimulation, glucose uptake and solute carrier family 2 (facilitated glucose transporter), member 4 (SLC2A4, formerly known as GLUT4) translocation were measured. Next the insulin signalling cascade was determined by submitting cells to lysis, immunoprecipitation and immunoblotting. RESULTS: NR1HR agonists ameliorate TNFalpha-induced insulin resistance restoring completely insulin-stimulated glucose uptake and SLC2A4 translocation to plasma membrane. This effect is parallel to the recovery of the insulin cascade insulin receptor/IRS-2/phosphatidylinositol 3-kinase/protein kinase B, and could be due to the fact that T0901317 prevents the increase of PTPN1 production and phosphatase activity produced by TNFalpha. In this regard, Ptpn1-deficient brown adipocytes showed protection against insulin resistance by TNFalpha. Moreover, we observed that T0901317 produced in itself a significant increase over basal glucose uptake consistent with an increase of SLC2A4 protein content in plasma membrane, attributable to the activation of protein kinase zeta and/or the increase of Slc2a4 expression. CONCLUSIONS/INTERPRETATION: Nuclear receptors NR1HR are interesting potential targets for drug treatment of insulin resistance.

Insulin-sensitizing effect of rosiglitazone (BRL-49653) by regulation of glucose transporters in muscle and fat of Zucker rats.

Thiazolidinediones (TZDs), a class of antidiabetic agents, are specific agonists of peroxisome proliferator activator receptor (PPARgamma). However, their mechanisms of action, and the in vivo target tissues that mediate insulin sensitization are not well understood. The aim of this study was to investigate the role of glucose transporters (GLUT-1 and GLUT-4) in the TZD insulin-sensitizer action. The effects of rosiglitazone treatment were studied using Zucker (fa/fa) rats after 7 days of oral dosing (3.6 mg/kg/d). Rosiglitazone lowered (approximate 80%) basal plasma insulin levels in obese rats and substantially corrected (approximately 50%) insulin resistance based upon results from hyperinsulinemic euglycemic clamp studies. GLUT-4 protein levels were reduced (approximately 75%) in adipose tissue of obese rats and treatment with rosiglitazone normalized them. Interestingly, GLUT-1 protein content was increased in adipose tissue ( thick approximate 150%) and skeletal muscle (approximately 50%) of obese rats and treatment with rosiglitazone increased it even more by 5.5-fold in fat and by 2.5-fold in muscle. Consistent with these results, basal (GLUT-1-mediated) transport rate of 3-O-methyl-D-glucose into isolated epitrochlearis muscle was elevated in response to rosiglitazone. Incubation of fully differentiated 3T3-L1 adipocytes with the drug for 7 days increased the levels of GLUT-1 protein, but did not affect GLUT-4 levels. In conclusion, rosiglitazone may improve insulin resistance in vivo by normalizing GLUT-4 protein content in adipose tissue and increasing GLUT-1 in skeletal muscle and fat. While the drug has a direct effect on GLUT-1 protein expression in vitro without a direct effect on GLUT-4 suggests that direct and indirect effects of rosiglitazone on glucose transporters may have an important role in improving insulin resistance in vivo.

Serine/threonine phosphorylation of IRS-1 triggers its degradation: possible regulation by tyrosine phosphorylation.

Insulin receptor substrate (IRS)-1 protein expression is markedly reduced in many insulin-resistant states, although the mechanism for this downregulation is unclear. In this study, we have investigated the early events in the insulin pathway that trigger the degradation of IRS-1. Incubation of the adipocytes with insulin induced a fast electrophoretic mobility shift of IRS-1 and a subsequent degradation of the protein. Wortmannin and rapamycin blocked this mobility shift of IRS-1, maintained the insulin-induced tyrosine phosphorylation of IRS-1, and blocked its degradation. In contrast, a glycogen synthase kinase 3 inhibitor, a mitogen-activated protein kinase/extracellular-regulated kinase inhibitor, and various protein kinase C inhibitors had no effect. Incubation with okadaic acid increased the serine/threonine phosphorylation of IRS-1 and its degradation, mimicking insulin, and its effect was prevented by the proteasome inhibitor lactacystin, as well as by rapamycin. Treatment of the cells with the tyrosine phosphatase inhibitor orthovanadate in the presence of insulin or okadaic acid partially inhibited the degradation of IRS-1. We propose that a rapamycin-dependent pathway participates as a negative regulator of IRS-1, increasing its serine/threonine phosphorylation, which triggers degradation. Thus, regulation of serine/threonine versus tyrosine phosphorylation may modulate IRS-1 degradation, affecting insulin sensitivity.

Regulation of proteins involved in insulin signaling pathways in differentiating human adipocytes.

In the present study we have examined the proteins involved in the insulin signaling cascade during and after differentiation of human adipocyte precursor cells and their correlation with glucose uptake. The differentiation of human adipocytes was characterized by a two- to threefold stimulation of glucose transport in response to insulin and a marked increase protein expression for the insulin receptor, IRS-1, GLUT-4, PI 3-kinase, and PKB, with respect to undifferentiated cells. In contrast, there were small changes in the protein expression of IRS-2, and no changes in PKC zeta and MAP kinases, although basal MAP kinase activity and GLUT-1 protein were reduced during differentiation. In conclusion, there are quantitative differences in the regulation of IRS-1 and other proteins during differentiation which may contribute to more efficient insulin signaling leading to glucose uptake in mature fat cells. Alterations in this pattern may reflect or contribute to an insulin-resistant state.

Phosphorylation of PDE3B by phosphatidylinositol 3-kinase associated with the insulin receptor.

Phosphatidylinositol 3-kinase mediates several actions of insulin including its antilipolytic effect. This effect is elicited by the insulin-stimulated serine phosphorylation and activation of cGMP-inhibited phosphodiesterase (PDE3B). In human adipocytes, we found that insulin differentially stimulated phosphatidylinositol 3-kinase activity; the lipid kinase activity was associated with IRS-1, whereas the serine kinase activity was associated with the insulin receptor and phosphorylated a number of proteins including p85, p110, and a 135-kDa protein identified as PDE3B. PDE3B phosphorylation was associated with enzyme activation, thus initiating the antilipolytic effect of insulin. These results show a novel pathway for intracellular signaling through the insulin receptor leading to the serine phosphorylation of key proteins involved in insulin action.

Impaired glucose transport and protein kinase B activation by insulin, but not okadaic acid, in adipocytes from subjects with Type II diabetes mellitus.

AIMS/HYPOTHESIS: To study the effects of insulin and okadaic acid, a serine/threonine phosphatase inhibitor which does not increase PI3-kinase activity, on the rate of glucose transport and protein kinase B activation in adipocytes from healthy subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus. METHODS: Adipocytes were incubated with or without insulin or okadaic acid or both and glucose transport, protein kinase B activity, phosphorylation and protein expression measured. RESULTS: Insulin and okadaic acid alone increased glucose uptake to a similar degree in adipocytes from healthy subjects and, when combined, exerted a partial additive effect. The effect of insulin was reduced by about 60% in adipocytes from Type II diabetic patients, whereas the effect of okadaic acid was essentially unchanged and no further increase was seen when okadaic acid and insulin were combined. Okadaic acid increased protein kinase B activity to a greater extent (two to threefold) than insulin but only slightly increased the serine phosphorylation of protein kinase B. Adipocytes from Type II diabetic subjects exhibited both an impaired sensitivity as well as a reduced total serine phosphorylation and activation of protein kinase B in response to insulin but protein kinase B activity in response to okadaic acid was intact. CONCLUSION/INTERPRETATION: These results show that the ability of insulin to increase glucose transport and activate protein kinase B is reduced in fat cells from Type II diabetic subjects. Protein kinase B can, however, be activated by agents like okadaic acid which bypass the upstream defects in the insulin signalling pathway in Type II diabetic cells and, thus, increase glucose uptake.

On the control of lipolysis in adipocytes.

The lipolytic reaction in adipocytes is one of the most important reactions in the management of bodily energy reserves, and dysregulation of this reaction may contribute to the symptoms of Type 2 diabetes mellitus. Yet, progress on resolving the molecular details of this reaction has been relatively slow. However, recent developments at the molecular level begin to paint a clearer picture of lipolysis and point to a number of unanswered questions. While HSL has long been known to be the rate-limiting enzyme of lipolysis, the mechanism by which HSL attacks the droplet lipids is not yet firmly established. Certainly, the immunocytochemical evidence showing the movement of HSL to the lipid droplet upon stimulation leaves little doubt that this translocation is a key aspect of the lipolytic reaction, but whether or not HSL phosphorylation contributes to the translocation, and at which site(s), is as yet unresolved. It will be important to establish whether there is an activation step in addition to the translocation reaction. The participation of perilipin A is indicated by the findings that this protein can protect neutral lipids within droplets from hydrolysis, but active participation in the lipolytic reaction is yet to be proved. Again, it will be important to determine whether mutations of serine residues of PKA phosphorylation sites of perilipins prevent lipolysis, and whether such modifications abolish the physical changes in the droplet surfaces that accompany lipolysis.

Insulin receptor substrate (IRS) 1 is reduced and IRS-2 is the main docking protein for phosphatidylinositol 3-kinase in adipocytes from subjects with non-insulin-dependent diabetes mellitus.

The large docking protein IRS-1 is a major substrate for the insulin receptor and other tyrosine kinases. It plays a key role in eliciting many of insulin's actions, including binding and activation of phosphatidylinositol (PI) 3-kinase and the subsequent increase in glucose transport. Gene disruption of IRS-1 in mice is associated with an impaired insulin-stimulated glucose disposal in vivo and glucose transport in vitro, but the survival of the animals and residual insulin sensitivity is dependent on the presence of the alternative docking protein IRS-2. We examined the expression and function of IRS-1 and IRS-2 in adipocytes from healthy and diabetic individuals. Cells from subjects with non-insulin-dependent diabetes mellitus (NIDDM), but not with insulin-dependent diabetes mellitus, had an impaired insulin effect and a marked reduction (70 +/- 6%) in the expression of IRS-1 protein, whereas IRS-2 was unchanged. In normal cells, IRS-1 was the main docking protein for the binding and activation of insulin-stimulated PI 3-kinase; IRS-2 was also functional but required a higher insulin concentration for a similar binding and activation of PI 3-kinase. In contrast in NIDDM cells with a low IRS-1 content, IRS-2 became the main docking protein. These findings may provide important reasons for the insulin resistance in NIDDM.

The inhibitory effect of staurosporine on insulin action is prevented by okadaic acid. Evidence for an important role of serine/threonine phosphorylation in eliciting insulin-like effects.

The serine/threonine phosphatase inhibitor, okadaic acid (OA), exerted several insulin-like effects in rat adipose cells and was, in part, synergistic with insulin. OA stimulated glucose transport activity, altered the electrophoretic mobility of IRS-1, increased the phosphorylation of the MAP-kinases ERK 1 and 2 on tyrosine sites, markedly increased MAP kinase activity and also acted synergistically with insulin in activating these enzymes. However, OA did not increase PI 3-kinase activity or the tyrosine phosphorylation of key upstream proteins in insulin's signaling cascade. Staurosporine virtually completely inhibited the insulin-stimulated glucose transport and MAP kinase activation in spite of a maintained high PI 3-kinase activity. In contrast, the effects of OA alone or in the presence of insulin were less, or not at all, affected. These data suggest that OA exerts an insulin-like effect through a serine/threonine-related pathway which is distinct from, but converges with, that of insulin downstream PI 3-kinase and upon which staurosporine exerts an inhibitory effect.

Okadaic acid exerts a full insulin-like effect on glucose transport and glucose transporter 4 translocation in human adipocytes. Evidence for a phosphatidylinositol 3-kinase-independent pathway.

The effects of the serine/threonine phosphatase inhibitor, okadaic acid, and insulin on glucose transport activity, glucose transporter 4 translocation to the plasma membrane, and the signaling pathway of insulin were examined in human adipocytes. Okadaic acid consistently produced a greater increase than insulin in the rate of glucose transport, and both agents together had a partial additive effect. Both insulin alone and okadaic acid alone stimulated the translocation of glucose transporter 4 to the plasma membrane. Insulin, but not okadaic acid, stimulated phosphatidylinositol 3-kinase (PI 3-kinase) activity, and wortmannin completely inhibited the effect of insulin on glucose transport. When the cells were incubated with both agents, okadaic acid inhibited insulin-stimulated PI 3-kinase activity but did not block the association of the p85 or p110 subunits of PI 3-kinase with insulin receptor substrate 1. Insulin-stimulated tyrosine phosphorylation of insulin receptor substrate 1 was only slightly reduced (15-30%) by okadaic acid. These data demonstrate that okadaic acid exerts a full insulin-like effect independent of the activation of PI 3-kinase. Thus, PI 3-kinase lipid kinase is not essential for glucose transporter 4 translocation in human adipocytes, and different pathways exist that lead to glucose transporter 4 translocation and increased glucose transport.

Perilipin: possible roles in structure and metabolism of intracellular neutral lipids in adipocytes and steroidogenic cells.

Perilipins are a family of unique proteins intimately associated with the limiting surface of neutral lipid storage droplets in adipocytes and in steroidogenic cells. Lipid hydrolysis in these cells is initiated by cAMP, which leads to phosphorylation of hormone-sensitive lipase in adipocytes and cholesteryl esterase in steroidogenic cells by protein kinase A. Although the concurrent phosphorylation of perilipin by this kinase suggests a role for these proteins in lipid breakdown, a role for these proteins in lipid packaging or in maintaining the lipid droplet structure cannot be excluded.

Perilipin is located on the surface layer of intracellular lipid droplets in adipocytes.

Immunocytochemistry was used to determine the intracellular location of perilipins in adipocytes and the occurrence of these proteins in tissues involved in triacylglycerol metabolism. Confocal microscopy and 3-dimensional analysis of 3T3-L1 adipocytes showed that perilipin immunofluorescence, present on the surfaces of all sized lipid droplets, appeared unevenly dispersed on the surfaces of many large lipid droplets. Electron microscopy revealed that immunogold staining for perilipin was located directly on the surface layer apposed to and surrounding the core triacylglycerol of intracellular lipid droplets of adipocytes in culture or from white and brown adipose tissue. Freeze-fracture electron microscopy indicated that the hydrophobic face of this surface monolayer contained particles identical in size and distribution to intramembranous particles (IMPs), which are unique structural features of the hydrophobic faces of bilayered membranes. Also, freeze-fracture replicas revealed areas of continuity between the surface layer of lipid droplets and the membrane leaflets of endoplasmic reticulum, suggesting that the droplet monolayer surface is an area of endoplasmic reticulum membrane leaflet modified by its unique content of perilipin. Microperoxisomes, identified by immunostaining for catalase, were found closely associated with lipid droplets, but external to and not in contact with the lipid droplet surface layer. Vimentin, identified by immunofluorescence, was present around the periphery of most lipid droplets in 3T3-L1 cells during early stages of adipocyte development but, in contrast to perilipins, vimentin was not around the periphery of many large lipid droplets in mature cells. Although perilipin was at the surface of lipid droplets in adipocytes of lactating mammary gland, none was found to be associated with the milk lipid droplets in alveolar epithelial cells, nor was the protein found on the surfaces of lipid droplets in hepatocytes. Studies in mammary gland show that perilipin immunostaining will be a valuable tool for the identification of tissue adipocytes severely depleted of their triacylglycerol stores and thus without their characteristic spherical shape. Perilipin's singular location on the surface monolayer of intracellular lipid droplets supports an intimate role for the protein in the triacylglycerol metabolic functions of adipocytes.

Role of insulin-like growth factor-1 on the kinetics of human lymphocytes stimulation in serum-free culture medium.

In a serum-free medium addition of insulin-like growth factor-1 (IGF-1) consistently enhanced lymphocyte proliferation response to PHA in a dose-dependent fashion. This effect was produced by an acceleration in the expression of clone expansion and not in the number of proliferating cells. This was documented by kinetics data obtained from the first proliferation round of PHA-stimulated lymphocytes, in which addition of IGF-1 reduced G1-phase length, without changing G0-phase, S-phase or cloned size. The data were confirmed in 10-day culture of stimulated lymphocytes where IGF-1 only accelerated cell proliferation without modifying the area enclosed by the proliferation curve. As IGF-1 is under the control of growth hormone, our results suggest that some of the immuno-regulation effects ascribed to growth hormone in vivo could be produced by IGF-1.

Aldosterone stimulated differentiation of mouse 3T3-L1 cells into adipocytes.

We find that 1-10 nM aldosterone can induce differentiation of 3T3-L1 cells into adipose cells as evaluated by microscopic accumulation of fat droplets and quantitative measurement of triglycerides and of glycerol-3-phosphate dehydrogenase, an enzyme specific for adipocyte differentiation. Moreover, the aldosterone antagonist ZK91587 inhibits aldosterone-but not glucocorticoid-mediated differentiation of 3T3-L1 cells. Steroid binding assays with 3T3-L1 cells indicate the presence of specific binding sites for aldosterone. We conclude that there is an aldosterone receptor-mediated pathway for terminal differentiation of 3T3-L1 cells into adipose cells. Receptors for aldosterone have also been found in a variety of cells that do not function to regulate sodium and potassium transport. The aldosterone receptor may have a role in regulation expression of genes involved in differentiation of these cells.

Identification of a protein factor secreted by 3T3-L1 preadipocytes inhibitory for the human MCF-7 breast cancer cell line.

The 3T3-L1 cell line is a preadipocyte cell line derived from the Swiss 3T3 mouse fibroblast cell line. We have compared the effect of 3T3-L1 conditioned medium (3T3-L1 CM) and Swiss 3T3 conditioned medium (3T3 CM) on the growth of normal mouse mammary cells (NMMG) and the human MCF-7 breast carcinoma cell line. 3T3 CM increased the growth of both NMMG and MCF-7 cells by 19 +/- 2% (SD) and 24 +/- 3%, respectively, and increased thymidine incorporation by 74 +/- 4% and 104 +/- 8%, respectively. Conditioned medium from 3T3-L1 cells stimulated the growth of NMMG cells by 64 +/- 2%; in contrast, 3T3-L1 CM inhibited the growth of MCF-7 cells by 36 +/- 1%. In parallel with these growth studies, thymidine incorporation increased by 20 +/- 4% in NMMG cells and decreased by 72 +/- 5% in the MCF-7 cells. Moreover, a similar effect was also noted in NCI H630 colon cancer cells, where 3T3-L1 CM produced a 58 +/- 4% decrease in growth and a 82 +/- 6% decrease in thymidine incorporation. Heating the 3T3-L1 CM at 100 degrees C for 30 min destroyed all inhibitory activity. Several known inhibitory growth factors (fibroblast growth factor, 20 ng/ml; interleukin 6, 1000 units/ml; tumor necrosis factor alpha, 15 ng/ml; transforming growth factor beta, 1 ng/ml) were tested for activity in the MCF-7 cells. Tumor necrosis factor alpha and transforming growth factor beta produced a 97% and 67% inhibition of thymidine uptake, respectively, whereas interleukin 6 and fibroblast growth factor had no effect. Neither transforming growth factor beta nor tumor necrosis factor alpha activity was detectable in 3T3-L1 CM using an enzyme-linked immunosorbent assay. High-performance liquid chromatography fractionation of the 3T3-L1 CM revealed that the inhibitory activity eluted at a molecular weight of 67,000; moreover, silver staining of these eluates on a denaturing polyacrylamide gel revealed that M(r) 69,000 peptide was the predominant protein band in the inhibitory fractions. Thus 3T3-L1 CM stimulates the growth of normal breast epithelial cells and inhibits the growth of MCF-7 breast cancer cells. This inhibitory activity appears to be due to a protein secreted by 3T3-L1 preadipocytes.

Progestins stimulate the differentiation of 3T3-L1 preadipocytes.

The effect of progesterone on the differentiation of the 3T3-L1 preadipocytes was investigated and compared with other sex steroids (estradiol and testosterone), with cortisol, with the synthetic progestin R5020 and with the progestin/glucocorticoid antagonist RU38486. At 10(-8) M, progesterone stimulated the activity of glycerol-3-phosphate dehydrogenase and triglyceride deposition. Progesterone, R5020, cortisol, and RU38486 increased triglycerides about 2-fold at 10(-7) M. Only minimal effects were observed with testosterone and estradiol even at 10(-6) M. When the cells were cultured in presence of 10(-5) M metyrapone the effect of progesterone was unchanged, suggesting that the progesterone was not metabolized to a glucocorticoid. Progesterone, R5020 and RU38486 competed efficiently with [3H]dexamethasone for the glucocorticoid receptor in 3T3-L1 cytosol. These results indicate a significant, reproducible dose-dependent effect of progestins on differentiation of the preadipocytes, which appears to be mediated via the glucocorticoid receptor.

Inhibitory effect of 11 beta-hydroxypregna-1,4-diene-3,20-dione (delta HOP) on lymphocyte proliferation.

We have compared the immunosuppressive effect of delta HOP and glucocorticoids on lymphocyte proliferation and IL-1 secretion. The new synthetic steroid only inhibited proliferation of phytohaemagglutinin (PHA)-stimulated human lymphocyte at high concentrations and the effect did not persist after washing out the steroid. In contrast, glucocorticoids produced the classical dose-response inhibition and the effect persisted when they were removed from the cultured medium. Although both steroids decreased IL-1 secretion from human monocytes stimulated with lipopolysaccharide (LPS), they exert the same effect through a different mechanism. The experiments we report suggest that the decrease of IL-1 synthesis produced by delta HOP could be caused by inhibition of LPS phagocytosis. These results support our hypothesis that delta HOP exerts its immunosuppressive and anti-inflammatory effect by a non-genomic mechanism.

Effect of 11 beta OH pregna-1,4-diene-3,20-dione (delta HOP) on thymocyte plasma membranes.

The effect of delta HOP on the formation of concanavalin A (Con A) caps and steady state anisotropy (rs) obtained in 1,6-diphenyl-1,3,5-hexatriene (DPH) labeled thymocyte plasma membranes was compared with the effect of glucocorticoids on these experiments. Results demonstrate that delta HOP decreased cap formation "in vivo" as well as "in vitro" and that it did not change fluorescence anisotropy "in vitro". Glucocorticoids had an opposite effect, increasing fluidity apparently through a glucocorticoid specific mechanism not exerted by delta HOP.

Effect of 11 beta OH pregna-1,4-diene-3,20-dione (delta HOP) on thymocyte plasma membranes.

The effect of delta HOP on the formation of concanavalin A (Con A) caps and steady state anisotropy (rs) obtained in 1,6-diphenyl-1,3,5-hexatriene (DPH) labeled thymocyte plasma membranes was compared with the effect of glucocorticoids on these experiments. Results demonstrate that delta HOP decreased cap formation [quot ]in vivo[quot ] as well as [quot ]in vitro[quot ] and that it did not change fluorescence anisotropy [quot ]in vitro[quot ]. Glucocorticoids had an opposite effect, increasing fluidity apparently through a glucocorticoid specific mechanism not exerted by delta HOP.