Adipose-derived regenerative cells and fat grafting for treating breast cancer-related lymphedema: Lymphoscintigraphic evaluation with 1 year of follow-up.

BACKGROUND: Breast cancer-related lymphedema (BCRL) is a feared late complication. Treatment options are lacking at present. Recent studies have suggested that mesenchymal stromal cells can alleviate lymphedema. Herein, we report the results from the first human pilot study with adipose-derived regenerative cells (ADRCs) for treating BCRL with 1 year of follow-up. MATERIAL AND METHODS: We included 10 patients with BCRL. ADRCs were injected directly into the axillary region together with a scar-releasing fat grafting procedure. Primary endpoint was change in arm volume. Secondary endpoints were change in patient-reported outcomes, changes in lymph flow, and safety. RESULTS: During follow-up, no significant change in volume was noted. Patient-reported outcomes improved significantly with time. Five patients reduced their use of conservative management. Quantitative lymphoscintigraphy did not improve on the lymphedema-affected arms. ADRCs were well tolerated, and only minor transient adverse events related to liposuction were noted. CONCLUSIONS: In this pilot study, a single injection of ADRCs improved lymphedema based on patient-reported outcome measures, and there were no serious adverse events during the follow-up period. Lymphoscintigraphic evaluation showed no improvement after ADRC treatment. There was no change in excess arm volume. Results of this trial need to be confirmed in randomized clinical trials.

Functional variation in the arginine vasopressin 2 receptor as a modifier of human plasma von Willebrand factor levels.

SUMMARY OBJECTIVES: Stimulation of arginine vasopressin 2 receptor (V2R) with arginine vasopressin (AVP) results in a rise in von Willebrand factor (VWF) and factor VIII plasma levels. We hypothesized that gain-of-function variations in the V2R gene (AVPR2) would lead to higher plasma levels of VWF and FVIII. METHODS AND RESULTS: We genotyped the control populations of two population-based studies for four AVPR2 variations: a-245c, G12E, L309L, and S331S. Rare alleles of a-245c, G12E, and S331S, which were in linkage disequilibrium, were associated with higher VWF propeptide, VWF and FVIII levels. The functionality of the G12E variant was studied in stably transfected MDCKII cells, expressing constructs of either 12G-V2R or 12E-V2R. Both V2R variants were fully glycosylated and expressed on the basolateral membrane. The binding affinity of V2R for AVP was increased three-fold in 12E-V2R-green fluorescent protein (GFP) cells, which is in accordance with increased levels of VWF propeptide associated with the 12E variant. The dissociation constant (K(D)) was 4.5 nm [95% confidence interval (CI) 3.6-5.4] for 12E-V2R-GFP and 16.5 nm (95% CI 10.1-22.9) for 12G-V2R-GFP. AVP-induced cAMP generation was enhanced in 12E-V2R-GFP cells. CONCLUSIONS: The 12E-V2R variant has increased binding affinity for AVP, resulting in increased signal transduction, and is associated with increased levels of VWF propeptide, VWF, and FVIII.

Normal levels of cerebrospinal fluid hypocretin-1 and daytime sleepiness during attacks of relapsing-remitting multiple sclerosis and monosymptomatic optic neuritis.

There is emerging evidence that multiple sclerosis (MS), the hypothalamic sleep-wake regulating neuropeptide hypocretin-1 (hcrt-1) and the sleep disorder narcolepsy may be connected. Thus, the major pathophysiological component of narcolepsy is lack of hcrt-1. Dysfunction of the hypocretin system has been reported in MS case reports with attacks of hypothalamic lesions, undetectable cerebrospinal fluid (CSF) hcrt-1 and hypersomnia, but not found during remission in small samples. Finally, daytime sleepiness, the major symptom of narcolepsy, is reported in several MS populations, and there are case reports of co-existent narcolepsy and MS. However, it is unknown whether hcrt-1 and daytime sleepiness generally change during MS attacks. We therefore analyzed whether daytime sleepiness (using the Epworth Sleepiness Scale (ESS)) and CSF hcrt-1 levels differed between MS attack and remission, in 48 consecutively referred patients with relapsing-remitting MS (RRMS) or monosymptomatic optic neuritis (MON). Twenty-seven patients were in attack and 21 in remission. ESS was normal both during attacks (5.4 +/- 3.0) and remission (5.8 +/- 2.6), and mean CSF hcrt-1 was normal (456 +/- 41 pg/ml). No statistically significant differences were found between attack and remission. MRI scans revealed no hypothalamic lesions. The results show that the hypocretin system is intact and sleepiness is not typical in RRMS and MON without hypothalamic lesions on MRI.

Differential G protein receptor kinase 2 expression in compensated hypertrophy and heart failure after myocardial infarction in the rat.

The onset of heart failure is associated with characteristic changes in myocardial expression of G protein receptor kinase 2 (GRK2). Although, GRK2 significantly contributes to the regulation of myocardial function in the failing heart, the GRK2 expression during cardiac hypertrophy without heart failure remains to be explored. We here report a differential expression of GRK2 in cardiac hypertrophy with or without heart failure in response to a myocardial infarction in the rat. Postmyocardial infarction animals were divided into two groups depending on the absence or presence of pulmonary edema, which is a manifestation of heart failure. Remarkably, cardiac GRK2 expression and activity were inhibited in animals with cardiac hypertrophy without heart failure, whereas animals with heart failure had elevated GRK2. Thus, three weeks after the infarction cardiac GRK2 expression in animals with hypertrophy alone was decreased to 0.34 of control, whereas in the group of animals with heart failure GRK2 expression was 1.89-fold higher than in sham-operated animals. GRK2 activity was affected in a similar way, three and nine weeks after the infarction cardiac GRK2 activity was reduced to 0.58 and 0.62 in animals with hypertrophy without heart failure when compared to sham operated animals. By contrast, GRK2 activity was increased by 1.32- and 1.21-fold three and nine weeks postinfarction in animals with heart failure when compared to sham animals. These data suggest that GRK2 expression is differentially regulated in hypertrophic, non-failing and hypertrophic, failing hearts.

G protein-coupled receptor kinase 2--a feedback regulator of Gq pathway signalling.

G protein coupled receptors or serpentine receptors work as signalling switches that turn extracellular signals into activation of multiple molecules at the intracellular face of the plasma membrane. Serpentine receptors are the targets of around 70% of all current drugs in clinical medicine. We suggest that these receptors can be pharmacologically targeted by modification of their unique internal inhibitors the G protein coupled receptor kinases (GRKs). The GRKs constitute a family of serine/threonine kinases that specifically bind to and phosphorylate agonist-activated serpentine receptors. The phosphorylated receptors are recognized by arrestins that bind to the receptor and uncouple them from attached G proteins thereby terminating G protein signalling. This review focuses on a ubiquitously expressed GRK family member dubbed GRK2 (previously called beta-adrenergic receptor kinase 1) that regulates cellular signalling at multiple levels. In Gq-coupled signalling modules GRK2 may function as a feedback inhibitor molecule that monitors, inhibits and re-directs the information flow. GRK2 acts as a negative feedback protein by interacting with at least six key signalling molecules in the Gq pathway including; receptors, free G beta gamma subunits, activated G alpha q subunits, phosphatidylinositol-4, 5-bisphosphate (PIP2), protein kinase C (PKC) and calmodulin (CaM). GRK signalling is important for immune, endocrine and cardiovascular function manifesting itself in disorders such as heart failure and lymphocyte activation especially in chronic inflammation. This review summarizes the advances made in understanding the many actions of GRKs and addresses their potential as novel therapeutic targets.

Functional reconstitution of the angiotensin II type 2 receptor and G(i) activation.

On the basis of the patterns of conserved amino acid sequence, the angiotensin II type 2 (AT(2)) receptor belongs to the family of serpentine receptors, which relay signals from extracellular stimuli to heterotrimeric G proteins. However, the AT(2) receptor signal transduction mechanisms are poorly understood. We have measured AT(2)-triggered activation of purified heterotrimeric proteins in urea-extracted membranes from cultured COS-7 cells expressing the recombinant receptor. This procedure removes contaminating GTP-binding proteins without inactivating the serpentine receptor. Binding studies using [(125)I] angiotensin (Ang) II revealed a single binding site with a K(d)=0.45 and a capacity of 627 fmol/mg protein in the extracted membranes. The AT(2) receptor caused a rapid activation of alpha(i) and alpha(o) but not of alpha(q) and alpha(s), as measured by radioactive guanosine 5'-3-O-(thio)triphosphate (GTPgammaS) binding. Activation required the presence of activated receptors, betagamma, and alpha subunits. As a first step aimed at developing an in vitro assay to examine AT(2) receptor pharmacology, we tested a battery of Ang II-related ligands for their ability to promote AT(1) or AT(2) receptor-catalyzed G(i) activation. Two proteolytic fragments of Ang II, Ang III and Ang1-7, also promoted activation of alpha(i) through the AT(2) receptor. Furthermore, we found that [Sar(1),Ala(8)]Ang II is an antagonist for both AT(1) and AT(2) receptors and that CPG42112 behaves as a partial agonist for the AT(2) receptor. In combination with previous observations, these results show that the AT(2) receptor is fully capable of activating G(i) and provides a new tool for exploring AT(2) receptor pharmacology and interactions with G-protein trimers.

Effect of glucagon-like peptide 1(7-36)amide in insulin-treated patients with diabetes mellitus secondary to chronic pancreatitis.

Diabetes mellitus secondary to chronic pancreatitis is characterized by a progressive destruction of the pancreas, including loss of the islet cells, leading to a form of diabetes that can mimic both type 1 and type 2 diabetes. Glucagon-like peptide 1(7-36)amide (GLP-1), an intestinally derived insulinotropic hormone, represents a potential therapeutic agent for type 2 diabetes, because exogenous GLP-1 has been shown to increase the insulin and reduce the glucagon concentrations in these patients, and thus induce lower blood glucose, but without causing hypoglycemia. Ten patients with diabetes mellitus secondary to chronic pancreatitis and five normal subjects were studied. Nine patients were treated with insulin and one patient with sulfonylurea. In the fasting state, saline or GLP-1 in doses of 0.4 or 1.2 pmol/min/kg body weight were infused intravenously for 4 hours. Blood glucose was reduced in all patients with both doses of GLP-1; plasma C-peptide increased (p<0.02), and plasma glucagon decreased (p<0.02) compared with basal levels, also in three patients with normoglycemia and high levels of presumably exogenous insulin. Similar results were obtained in the normal subjects. In conclusion, GLP-1 treatment may be considered in patients with diabetes mellitus secondary to chronic pancreatitis, provided that a certain amount of alpha- and beta-cell secretory capacity is still present.

Similar structures and shared switch mechanisms of the beta2-adrenoceptor and the parathyroid hormone receptor. Zn(II) bridges between helices III and VI block activation.

The seven transmembrane helices of serpentine receptors comprise a conserved switch that relays signals from extracellular stimuli to heterotrimeric G proteins on the cytoplasmic face of the membrane. By substituting histidines for residues at the cytoplasmic ends of helices III and VI in retinal rhodopsin, we engineered a metal-binding site whose occupancy by Zn(II) prevented the receptor from activating a retinal G protein, Gt (Sheikh, S. P., Zvyaga, T. A. , Lichtarge, O., Sakmar, T. P., and Bourne, H. R. (1996) Nature 383, 347-350). Now we report engineering of metal-binding sites bridging the cytoplasmic ends of these two helices in two other serpentine receptors, the beta2-adrenoreceptor and the parathyroid hormone receptor; occupancy of the metal-binding site by Zn(II) markedly impairs the ability of each receptor to mediate ligand-dependent activation of Gs, the stimulatory regulator of adenylyl cyclase. We infer that these two receptors share with rhodopsin a common three-dimensional architecture and an activation switch that requires movement, relative to one another, of helices III and VI; these inferences are surprising in the case of the parathyroid hormone receptor, a receptor that contains seven stretches of hydrophobic sequence but whose amino acid sequence otherwise shows no apparent similarity to those of receptors in the rhodopsin family. These findings highlight the evolutionary conservation of the switch mechanism of serpentine receptors and help to constrain models of how the switch works.

C5a receptor activation. Genetic identification of critical residues in four transmembrane helices.

Hormones and sensory stimuli activate serpentine receptors, transmembrane switches that relay signals to heterotrimeric guanine nucleotide-binding proteins (G proteins). To understand the switch mechanism, we subjected 93 amino acids in transmembrane helices III, V, VI, and VII of the human chemoattractant C5a receptor to random saturation mutagenesis. A yeast selection identified 121 functioning mutant receptors, containing a total of 523 amino acid substitutions. Conserved hydrophobic residues are located on helix surfaces that face other helices in a modeled seven-helix bundle (Baldwin, J. M., Schertler, G. F., and Unger, V. M. (1997) J. Mol. Biol. 272, 144-164), whereas surfaces predicted to contact the surrounding lipid tolerate many substitutions. Our analysis identified 25 amino acid positions resistant to nonconservative substitutions. These appear to comprise two distinct components of the receptor switch, a surface at or near the extracellular membrane interface and a core cluster in the cytoplasmic half of the bundle. Twenty-one of the 121 mutant receptors exhibit constitutive activity. Amino acids substitutions in these activated receptors predominate in helices III and VI; other activating mutations truncate the receptor near the extracellular end of helix VI. These results identify key elements of a general mechanism for the serpentine receptor switch.

Neuropeptide Y2 receptors on nerve endings from the rat neurohypophysis regulate vasopressin and oxytocin release.

Neuropeptide Y and peptide YY are important central and peripheral modulators of cardiovascular and neuroendocrine functions, that act through multiple receptor subtypes, Y1 through Y5. A neuropeptide Y-binding site of the Y2 type was characterized by ligand-binding studies in isolated nerve terminals from the rat neurohypophysis. Functionally, neuropeptide Y and peptide YY dose-dependently triggered arginine 8-vasopressin and oxytocin release from perfused isolated terminals, and potentiated the arginine-8-vasopressin release induced by depolarization. Osmotic stimulation by salt loading of rats for two and seven days caused a more than three-fold increase in the neuropeptide Y content of the nerve endings. However, the Y2 receptor expression and arginine-8-vasopressin content declined, showing that the neuropeptide Y system is dynamic and suggesting that it plays a physiological role in salt and water homeostasis. Two sets of observations suggest the arginine-8-vasopressin release by neuropeptide Y may not be explained by neuropeptide Y effects on intracellular Ca2+. First, absence of Ca2+ from the perfusion medium did not affect the arginine-8-vasopressin release, and secondly neuropeptide Y did not change intraterminal Ca2+ concentrations. Pretreatment with pertussis toxin blocked arginine-8-vasopressin secretion by neuropeptide Y, suggesting activation of Gi or Go heterotrimeric G-proteins are required for secretion. It is concluded, that the nerve endings of the neurohypophysis contain a complete neuropeptide Y system with ligand and receptors. Neuropeptide Y may act in an autocrine fashion via activation of Y2 neuropeptide Y receptors to stimulate the release of vasopressin and oxytocin via a Gi/Go dependent secretory mechanism.

Reduction of neuropeptide Y binding sites in the rat hippocampus after electroconvulsive stimulations.

Repetitive electroconvulsive stimulations (ECSs) increase neuropeptide Y (NPY) synthesis in hippocampal neurons, but whether NPY release and the density of NPY receptors are affected is unknown. In rats exposed to 14 daily ECSs, the concentration of NPY specific binding sites in hippocampal membranes was reduced by about 75% compared with sham, but was unchanged in membranes isolated from the cerebral cortex and the thalamus. In accordance with this, in vitro autoradiography revealed a similar reduction in binding in the dentate gyrus and the CA1 and CA3 regions, but not in the parietal cortex, the entorhinal cortex or the thalamus. These results show significant changes in NPY receptor binding after repeated ECSs, suggesting that NPYergic neurotransmission, most likely within the hippocampus, is strongly affected by ECSs.

The effect of neuropeptides on vessel tone and cAMP production.

The effect of VIP, PHM, PHV, PACAP-27, and PACAP-38 on vessel tone and cAMP production was investigated in rabbit ovarian arteries in vitro. The peptides (10(-7)M) induced a significant relaxation on NA-precontracted vessels and displayed similar potencies. The cAMP accumulation induced by PACAP-27 and PACAP-38 was five times higher than the cAMP content induced by VIP, PHM, and PHV. NPY (10(-7)M) markedly reversed the relaxations induced by VIP, PHM, PHV, PACAP-27, and PACAP-38 but did not at all affect the cAMP production induced by these peptides. We conclude that the relaxation induced by VIP, PHM, PHV, PACAP-27, and PACAP-38 and the contraction evoked by NPY are not solely related to the changes of cAMP contents, and that in addition to cAMP, another intracellular signal transduction pathway may be involved.

Central administration of GLP-1-(7-36) amide inhibits food and water intake in rats.

Glucagon-like peptide (GLP)-1-(7-36) amide and its pancreatic receptors are important for control of blood glucose levels. However, rat GLP-1 receptors are also localized in the brain, in hypothalamus, and in areas without a blood-brain barrier. When rats were kept on a food restriction schedule, intracerebroventricular injection of GLP-1 just before food was offered inhibited food intake. However, peripheral GLP-1 administration by intraperitoneal injection had little effect. GLP-1 effects on water intake and output were also investigated. Intracerebroventricular GLP-1 profoundly inhibited angiotensin II-induced drinking behavior in rats, and water intake was suppressed by exogenous GLP-1 in rats habituated to a water restriction schedule. These effects were reproduced by intraperitoneal administration of GLP-1. Furthermore, intracerebroventricular GLP-1 stimulated urinary excretion of water and sodium. The centrally elicited effects were blocked by the GLP-1 antagonist exendin-(9-39) amide, whereas the N-terminally extended and inactive GLP-1-(1-36) amide had no effect on feeding and drinking. GLP-1 had no effect in behavioral assays measuring exploratory locomotor activity and conditioned taste aversion. In conclusion, GLP-1 may play a physiological role in regulation of both ingestion and the water and salt homeostasis.

Rhodopsin activation blocked by metal-ion-binding sites linking transmembrane helices C and F.

A large superfamily of receptors containing seven transmembrane (TM) helices transmits hormonal and sensory signals across the plasma membrane to heterotrimeric G proteins at the cytoplasmic face of the membrane. To investigate how G-protein-coupled receptors work at the molecular level, we have engineered metal-ion-binding sites between TM helices to restrain activation-induced conformational change in specific locations. In rhodopsin, the photoreceptor of retinal rod cells, we substituted histidine residues for natural amino acids at the cytoplasmic ends of the TM helices C and F. The resulting mutant proteins were able to activate the visual G protein transducin in the absence but not in the presence of metal ions. These results indicate that the TM helices C and F are in close proximity and suggest that movements of these helices relative to one another are required for transducin activation. Thus a change in the orientations of TM helices C and F is likely to be a key element in the mechanism for coupling binding of ligands (or isomerization of retinal) to the activation of G-protein-coupled receptors.

Vascular effects and cyclic AMP production produced by VIP, PHM, PHV, PACAP-27, PACAP-38, and NPY on rabbit ovarian artery.

The relationship between vessel tone and cAMP production induced by vasoactive intestinal polypeptide (VIP), peptide histidine methionine (PHM), peptide histidine valine (PHV), pituitary adenylate cyclase activating polypeptide (PACAP-27 and PACAP-38), and neuropeptide Y (NPY) was investigated in rabbit ovarian arteries in vitro. VIP, PHM, PHV, PACAP-27, and PACAP-38 added in single-dose experiments (10(-9), 10(-8), 10(-7), and 10(-6) M) induced all a significant dose-related relaxation of noradrenaline (NA)-precontracted vessels and displayed similar potencies. VIP, PHM, PHV, PACAP-27, and PACAP-38 all increased cyclic adenosine monophosphate (cAMP) accumulation. The cAMP accumulation induced by PACAP-27 and PACAP-38 was five times higher than the cAMP content induced by the other three peptides. The peptide-induced smooth muscle relaxation did not correlate to the cAMP accumulation. NPY (10(-7) M) markedly reversed the relaxations induced by VIP, PHM, PHV, PACAP-27, and PACAP-38, but did not influence the cAMP production induced by these peptides. In conclusion, the relaxation induced by VIP, PHM, PHV, PACAP-27, and PACAP-38 and the contraction induced by NPY are not solely related to the changes of cAMP contents. These findings indicate that in addition to cAMP, another intracellular signal transduction pathway may be involved in the relaxation and contraction induced by these peptides in rabbit ovarian artery.

Distribution of GLP-1 binding sites in the rat brain: evidence that exendin-4 is a ligand of brain GLP-1 binding sites.

The distribution and biochemical properties of glucagon-like peptide (GLP)-1(7-36) amide (GLP-1) binding sites in the rat brain were investigated. By receptor autoradiography of tissue sections, the highest densities of [125I]GLP-1 binding sites were identified in the lateral septum, the subfornical organ (SFO), the thalamus, the hypothalamus, the interpenduncular nucleus, the posterodorsal tegmental nucleus, the area postrema (AP), the inferior olive and the nucleus of the solitary tract (NTS). Binding studies with [125I][Tyr39] exendin-4, a GLP-1 receptor agonist, showed an identical distribution pattern of binding sites. Binding specificity and affinity was investigated using sections of the brainstem containing the NTS. Binding of [125I]GLP-1 to the NTS was inhibited concentration-dependently by unlabelled GLP-1 and [Tyr39]exendin-4 with KI values of 3.5 and 9.4 nM respectively. Cross-linking of hypothalamic membranes with [125I]GLP-1 or [125I][Tyr39]exendin-4 identified a single ligand-binding protein complex with a molecular mass of 63,000 Da. The fact that no GLP-1 binding sites were detected in the cortex but that they were detected in the phylogenetically oldest parts of the brain emphasizes that GLP-1 may be involved in the regulation of vital functions. In conclusion, the biochemical data support the idea that the central GLP-1 receptor resembles the peripheral GLP-1 receptor. Furthermore, the presence of GLP-1 binding sites in the circumventricular organs suggests that these may be receptors which act as the target for both peripheral blood-borne GLP-1 and GLP-1 in the nervous system.

Identification of specific binding sites for glucagon-like peptide-1 on the posterior lobe of the rat pituitary.

Glucagon-like peptide-1 (GLP-1) immunoreactivity has been found in autonomic and neuroendocrine brain regions, whereas only limited data are available regarding the characterization and localization of brain GLP-1 receptors. In the present study, using quantitative in vitro autoradiography, a high density of specific binding sites for GLP-1 was characterized on sections of the posterior pituitary lobe of the rat. Low specific binding of radiolabeled GLP-1 was found in the anterior lobe and no specific binding in the intermediate lobe. To examine the specificity of GLP-1 binding sites, sections of the posterior lobe were incubated with radiolabeled GLP-1 in the presence of various peptides. Radiolabeled [Tyr39]exendin-4, a specific GLP-1 agonist, bound to these receptor sites with the same affinity as GLP-1, while glucagon and vasoactive intestinal peptide (VIP) were unable to displace 125I-GLP-1. Both unlabeled exendin-4 and GLP-1 inhibited this binding with equally high affinity. Using 125I-[Tyr39]exendin-4 as radiolabel, the concentration of biding sites was found to be 7.8 +/- 0.4 fmol/mg tissue. Further analysis of the binding data from experiments with tissue slices revealed the presence of high and low affinity binding sites. In experiments with unlabeled [Tyr39]exendin-4, the KdS were 6.2 +/- 1.4 x 10(-12) and 9.3 +/- 1.5 x 10(-10) M, respectively, and in experiments with unlabeled GLP-1, 3.4 +/- 1.8 x 10(-12) and 5.9 +/- 1.5 x 10(-10) M, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Coupling of the human Y2 receptor for neuropeptide Y and peptide YY to guanine nucleotide inhibitory proteins in permeabilized SMS-KAN cells.

Using guanine nucleotides, pertussis toxin, and specific antisera against the COOH-terminals of the alpha-subunits of Gi1/2, Gi3, and G(o), the binding and biological response of the Y2 receptor (Y2R) for peptide YY (PYY) was probed in SMS-KAN neuroblastoma cells. The specific binding of radiolabeled PYY exhibited a single apparent dissociation constant, KD = 76 pM for intact cells and KD = 906 pM for permeabilized cells. However, other data suggested existence of multiple receptor affinity states. A shift in KD and a decrease in apparent number of binding sites (Bmax) was observed in permeabilized cells when incubated with guanine nucleotides. By contrast, in membrane preparations guanine nucleotides induced only a decrease in Bmax. In intact cells, agonist exposure inhibited the intracellular accumulation of forskolin-stimulated cyclic AMP by 80% (IC50 = 420 nM) compared with 94% inhibition (IC50 = 380 nM) in permeabilized cells. In permeabilized cells, preincubation with antisera against alpha i1/2 and alpha i3 blocked the functional response of PYY, with anti-alpha i3 being the most potent; whereas anti-alpha o failed to affect the cyclic AMP levels. These results suggest that permeabilized SMS-KAN cells serve as a good model system for analysis of Y2R binding kinetics and functional response and that the Y2R interacts directly with several different GiS (but not G(o)).