Immunological analysis of plasminogen activators from normal and transformed hamster cells. Evidence that the plasminogen activators produced by SV40 virus-transformed hamster embryo cells and normal hamster lung cells are antigenically identical.

Rabbits were immunized against the plasminogen activator released by SV4- virus-transformed hamster embryo cells. The resulting antiplasminogen activator immunoglobulin (APA-IgG) inhibited the enzymatic activity of the plasminogen activator produced by SV40-transformed hamster cells, and the plasmin-catalyzed release of these cells from the tissue culture dish. APA-IgG was not cytotoxic for these cells even in the presence of complement and did not inhibit their release of plasminogen activator. APA-IgG formed a single precipitin line in immunodiffusion plates using highly purified plasminogen activator as antigen. APA-IgG inhibited the plasminogen activator produced by newborn hamster lung cells and by an established diploid line (DON) of hamster lung cells, but did not inhibit plasminogen activators produced by normal or transformed hamster kidney cells or by cells of other species (mouse and human). We derive three major conclusions from these data: (a) There are several immunologically distinguishable forms (isozymes) of plasminogen activators in normal hamster tissues. (b) The plasminogen activators produced by normal hamster lung cells and by SV40 virus-transformed hamster embryo cells share antigenic determinants and are presumably the same isozyme. (c) The plasminogen activators produced by different hamster tumor cells do not share antigenic determinants and are presumably different isozymes.

Effect of sodium butyrate on lymphocyte activation.

Butyrate, in relatively low concentrations, has been shown to induce synthesis of enzymes, cause changes in cell morphology, and inhibit growth of a variety of mammalian cells in tissue culture (reviewed in [1]). In this communication, we report our observations on the effect of butyrate on lymphocyte activation. Butyrate completely and reversibly inhibits mitogen-induced blast formation. We present evidence that it does not interfere with the binding of mitogens, that it does not inhibit a number of the "early" reactions involved in activation, and that it does not affect ongoing DNA synthesis for an extended period of time. However, butyrate rapidly inhibits any increase in the rate of DNA synthesis.

Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes.

IL-6 is a cytokine with pleiotropic biological functions, including induction of the hepatic acute phase response and differentiation of activated B cells into Ig-secreting plasma cells. We found that human peripheral blood monocytes express the IL-6-R, which is undetectable on the large majority of lymphocytes of healthy individuals. Stimulation of monocytes by endotoxin or IL-1 causes a rapid downregulation of IL-6-R mRNA levels and a concomitant enhancement of IL-6 mRNA expression. IL-6 itself was found to suppress the IL-6-R at high concentrations. A gradual decrease of IL-6-R mRNA levels was observed along in vitro maturation of monocytes into macrophages. We show that downregulation of IL-6-R mRNA levels by IL-1 and IL-6 is monocyte specific, since IL-6-R expression is stimulated by both IL-1 and IL-6 in cultured human primary hepatocytes. Our data indicate that under noninflammatory conditions, monocytes may play a role in binding of trace amounts of circulating IL-6. Repression of monocytic IL-6-R and stimulation of hepatocytic IL-6-R synthesis may represent a shift of the IL-6 tissue targets under inflammatory conditions.

Hypomethylation of DNA during differentiation of Friend erythroleukemia cells.

DNA from mammalian cells has been shown to contain significant amounts of 5-methyl cytosine resulting from enzymatic transfer of methyl groups from s-adenosylmethionine to cytosine residues in the DNA polymer. The function of this modification is not known. We have found that DNA synthesized during chemically induced differentiation of friend erythroleukemia cells is hypomethylated, as measured by its ability to accept methyl groups transferred by homologous DNA methyltransferases in vitro. The extent of hypomethylation detected by this sensitive method is small, a decrease of less than 1.6 percent in 5-methylcytosine content. Hypomethylated DNA can be isolated from friend erythroleukemia cells grown in the presence of dimethyl sulfoxide, butyrate, hexamethylene-bis- acetamide, pentamethylene-bis acetamide, and ethionine. However, hypomethylated DNA is found only under conditions where differentiation is actually induced. DNA isolated from cells of a dimethyl sulfoxide- resistant subclone grown in the presence of that agent is not hypomethylated, although DNA of these cells becomes hypomethylated after growth in the presence of inducers that can trigger their differentiation. We also find that the DNA of friend erythroleukemia cells does not become hypomethylated when the cells are exposed to inducing agents in the presence of substances that inhibit differentiation. These results suggest a close link between genome modification by methylation and differentiation of friend erythroleukemia cells.

Identification of protein-binding sites in the hepatitis B virus enhancer and core promoter domains.

We have investigated the role of liver-specific trans-acting factor(s) in the regulation of hepatitis B virus (HBV) gene expression. A recorder plasmid (pEcoAluCAT; HBV nucleotides 1 through 1878) was constructed containing the HBV enhancer and the promoter region of the pregenomic RNA, which was ligated to the bacterial chloramphenicol acetyltransferase (CAT) gene. Upon transfecting this plasmid into various cell lines, the CAT gene was expressed only in cells of liver origin. Moreover, competition cotransfections with pEcoAluCAT and plasmids containing HBV enhancer sequences in human hepatoblastoma-derived HepG2 cells indicated the presence of titratable trans-acting factor(s) in these cells. Gel mobility shift assays using HBV enhancer and core promoter domains confirmed the existence of sequence-specific DNA-binding proteins in liver cell nuclear extract which bound to these regions. These binding sites encompass 17- and 12-nucleotide palindromes in the HBV enhancer and core promoter domains, respectively, when mapped by the methylation interference assay.

Specific binding to protein kinase C by ingenol and its induction of biological responses.

We have examined the ability of ingenol to bind to and activate protein kinase C and to induce similar responses to the phorbol esters in biological systems. The rationale was that ingenol possesses the critical functionalities of the phorbol ester pharmacophore with the exception of the hydrophobic domain; it might therefore possess weak potency, although previous reports had indicated that ingenol was biologically inactive. Our data demonstrate that ingenol indeed binds to protein kinase C with a Ki of 30 microM and activates the enzyme. In addition, ingenol was biologically active in 3 separate cell systems, showing effects similar to the phorbol esters on morphological change, cell-cell communication, epidermal growth factor binding, arachidonic acid metabolite release, and ornithine decarboxylase activity. The 50% effective concentration values for the biological activity of ingenol were between 30 microM and 1 mM, varying somewhat with the cell system and type of response. The biological activity of ingenol in general supports the proposed models of the phorbol ester pharmacophore and imposes additional experimental constraints that the modeling must satisfy.

L-Ethionine as an inducer of differentiation in human promyelocytic leukemia cells (HL-60).

The methionine analog, L-ethionine, induces morphological and biochemical changes in cultured HL-60 cells which are indicative of myeloid maturation. After 3 to 5 days of growth in the presence of L-ethionine, the majority of cells have enhanced phagocytic ability. The percentage of cells in the culture which bear complement receptors and which can respond to 12-O-tetradecanoylphorbol-13-acetate with respiratory burst activity increases more than 3-fold. Since the cells fail to become adherent and lose nonspecific esterase activity, we conclude that L-ethionine, like dimethyl sulfoxide, induces granulocytic differentiation of HL-60 cells.

Erythropoietin and erythropoietin receptor expression in human cancer.

Erythropoietin (EPO) stimulates the growth of erythroblasts in the bone marrow (C. Lacombe and P. Mayeux, NEPHROL: DIAL: TRANSPLANT:, 14 (SUPPL: 2): 22-28, 1999). We report basal and hypoxia-stimulated expression of EPO and its receptor, EPOR, in human breast cancer cells, and we demonstrate EPO-stimulated tyrosine phosphorylation and the proliferation of these cells in vitro. In 50 clinical specimens of breast carcinoma, we report high levels of EPO and EPOR associated with malignant cells and tumor vasculature but not with normal breast, benign papilloma, or fibrocystic tissue. Hypoxic tumor regions display the highest levels of EPO and EPOR expression. Enhanced EPO signaling may contribute to the promotion of human cancer by tissue hypoxia.

Effect of L-ethionine on macromolecular synthesis in mitogen-stimulated lymphocytes.

2--4 mM L-ethionine completely inhibits DNA synthesis in phytohaemagglutinin- or concanavalin A-stimulated lymphocytes even though it does not prevent the morphological changes characteristic of blast formation. Evidence is presented which indicates that complete commitment to DNA synthesis as well as a substantial increase in the rates of RNA and protein synthesis can occur in the presence of ethionine. Ethionine, however, does inhibit methylation of tRNA and prevents mitogen-induced increase in the activity of histone-modifying enzymes. All of these effects of exposure to ethionine are completely reversible. Removal of ethionine after 24 h or more of exposure results in a rapid, synchronous wave of DNA synthesis, an increase in the rate of methylation of RNA and an increase in activity of histone-modifying enzymes.

Regulation of interleukin-6 receptor expression in human monocytes and hepatocytes.

Human blood monocytes normally express the interleukin-6 receptor. Treatment of cultured monocytes with endotoxin, interleukin-1 beta, or interleukin-6 results in a decrease in interleukin-6 receptor mRNA levels. Glucocorticoids aso cause a drop in monocytic interleukin-6 receptor mRNA levels. We also found interleukin-6 receptor expression in cultured human hepatocytes, but in contrast to monocytes, where interleukin-6 receptor mRNA is presented by the ligand and by interleukin-1, treatment of hepatocytes with interleukin-6 or interleukin-1 resulted in increased interleukin-6 receptor mRNA levels. Induction of interleukin-6 receptor mRNA in hepatocytes was less pronounced when glucocorticoids were omitted from the culture medium. We conclude that during noninflammatory homeostasis, blood monocytes are involved in binding of trace amounts of circulating interleukin-6. During inflammatory events, the main target of interleukin-6 may be changed from the monocytic population not only to activated B-cells, but also to the hepatocytes.

The stimulation of capsaicin-sensitive neurones in a vanilloid receptor-mediated fashion by pungent terpenoids possessing an unsaturated 1,4-dialdehyde moiety.

1. The irritant fungal terpenoid isovelleral caused protective eye-wiping movements in the rat upon intraocular instillation and showed cross-tachyphylaxis with capsaicin, the pungent principle in hot pepper. 2. Isovelleral induced a dose-dependent calcium uptake by rat dorsal root ganglion neurones cultured in vitro with an EC50 of 95 nM, which was fully inhibited by the competitive vanilloid receptor antagonist capsazepine. 3. Isovelleral inhibited specific binding of [3H]-resiniferatoxin (RTX), an ultrapotent capsaicin analogue, to rat trigeminal ganglion or spinal cord preparations with an IC50 of 5.2 microM; in experiments in which the concentration of [3H]-RTX was varied, isovelleral changed both the apparent affinity (from 16 pM to 37 pM) and the co-operativity index (from 2.1 to 1.5), but not the Bmax. 4. The affinity of isovelleral for inducing calcium uptake or inhibiting RTX binding was in very good agreement with the threshold dose (2.2. nmol) at which it provoked pungency on the human tongue. 5. For a series of 14 terpenoids with an unsaturated 1,4-dialdehyde, a good correlation was found between pungency on the human tongue and affinity for vanilloid receptors on the rat spinal cord. 6. The results suggest that isovelleral-like compounds produce their irritant effect by interacting with vanilloid receptors on capsaicin-sensitive sensory neurones. Since these pungent diterpenes are structurally distinct from the known classes of vanilloids, these data provide new insights into structure-activity relations and may afford new opportunities for the development of drugs targeting capsaicin-sensitive pathways.

[3H]resiniferatoxin binding by the human vanilloid (capsaicin) receptor.

We report here that we were able to detect the human vanilloid receptor in all three major central endings of primary afferent neurons--in the dorsal horn of the spinal cord, in the cuneate and gracile nuclei and in the spinal nucleus of the trigeminal nerve--and to characterize the binding properties of the receptor in the dorsal horn. Specific [3H]resiniferatoxin (RTX) binding is thought to represent the vanilloid (capsaicin) receptor. [3H]RTX binding to membranes obtained from total human spinal cord and dorsal horn followed sigmoidal saturation kinetics indicating apparent positive cooperativity. The cooperativity index determined by fitting the data to the Hill equation was 1.37 +/- 0.02 in the total spinal cord and 1.77 +/- 0.16 in the dorsal horn. The apparent dissociation constants in whole spinal cord and dorsal horn membranes were 915 +/- 12 and 532 +/- 27 pM; the receptor densities were 140 +/- 6 and 227 +/- 15 fmol/mg protein, respectively. Membrane preparations from the spinal nucleus of the trigeminal nerve and the cuneate and gracile nuclei also bound [3H]RTX in a similar fashion. In parallel experiments, rat spinal cord membranes bound [3H]RTX with 20- to 40-fold higher affinity, somewhat greater positive cooperativity, but at a 3-fold lower receptor density. As predicted by the modified Hill equation, non-radioactive RTX at low receptor occupancy produced biphasic competition curves.(ABSTRACT TRUNCATED AT 250 WORDS)

Distinct structure-activity relations for stimulation of 45Ca uptake and for high affinity binding in cultured rat dorsal root ganglion neurons and dorsal root ganglion membranes.

The [3H]resiniferatoxin (RTX) binding assay using membrane preparations has been used to identify and characterize the vanilloid receptors in the central and peripheral nervous system of different species. In the present study, using cultured adult rat dorsal root ganglion neurons either in suspension or attached to the tissue culture plates, we developed an assay to measure specific [3H]RTX binding by the intact cells. We were able to characterize the vanilloid binding characteristics of the neurons and compared those to the properties of vanilloid binding sites present in rat dorsal root ganglia membrane preparations. We found that [3H]RTX bound with similar affinity and positive cooperativity to attached neurons (cultured for 5 days before being assayed), neurons in suspension (using a filtration assay) and dorsal root ganglion membrane preparations. Dissociation constants obtained in the three assays were 47.6 +/- 3.5 pM, 38.4 +/- 3.1 pM and 42.6 +/- 3.1 pM, respectively. The cooperativity indexes determined by fitting the data to the Hill equation were 1.73 +/- 0.11, 1.78 +/- 0.12 and 1.78 +/- 0.09, respectively. The maximal binding capacity was 0.218 +/- 0.026 fmol/10(3) cells and 0.196 +/- 0.021 fmol/10(3) cells in the case of the attached cells and cells in suspension, respectively. Nonradioactive RTX, capsaicin, capsazepine and resiniferonol 20-homovanillylamide fully displaced specifically bound [3H]RTX from cells in suspension with Ki and Hill coefficient values of 42.5 +/- 5.3 pM, 2.06 +/- 0.16 microM, 3.16 +/- 0.21 microM and 32.4 +/- 4.1 nM and 1.79 +/- 0.17, 1.68 +/- 0.06, 1.72 +/- 0.11 and 1.81 +/- 0.12, respectively. Structure-activity analysis of different vanilloid derivatives revealed that the various compounds have distinct potencies for receptor binding and inducing 45Ca uptake in rat dorsal root ganglion neurons. Affinities for receptor binding and stimulation of 45Ca uptake of RTX, resiniferonol 20-homovanillylamide, RTX-thiourea, tinyatoxin, phorbol 12,13-dibenzoate 20-homovanillylamide and capsaicin were 38.5 +/- 2.9 pM, 25.7 +/- 3.0 nM, 68.5 +/- 3.8 nM, 173 +/- 25 pM, 7.98 +/- 0.83 microM and 4.93 +/- 0.35 microM as compared to 0.94 +/- 0.12 nM, 26.5 +/- 3.5 nM, 149 +/- 30 nM, 1.46 +/- 0.25 nM, 1.41 +/- 0.48 microM and 340 +/- 57 nM. Computer fitting of the data yielded Hill coefficient values indicating positive cooperativity of receptor binding; however, stimulation of 45Ca uptake appeared to follow a non-cooperative mechanism of action. The competitive capsaicin antagonist capsazepine inhibited specific binding of [3H]RTX by rat dorsal root ganglion membrane preparations with Ki and Hill coefficient values of 3.89 +/- 0.38 microM and 1.74 +/- 0.11. On the other hand it inhibited the induction of 45Ca uptake into the cells induced by capsaicin and RTX in a non-cooperative fashion with Ki values of 271 +/- 29 nM and 325 +/- 47 nM. Our results show that the membrane binding assay relates to the reality of receptor function in the intact, cultured neurons, both in terms of affinity and positive cooperativity. However the different vanilloid derivatives displayed markedly distinct structure-activity relations for high affinity receptor binding and stimulation of 45Ca uptake into rat dorsal root ganglion neurons. Among various explanations for this discrepancy, we favor the possibility that the two assays detect distinct classes of the vanilloid (capsaicin) receptor present in primary sensory neurons.

Differential expression of E-cadherin in lobular and ductal neoplasms of the breast and its biologic and diagnostic implications.

We studied the pattern of E-cadherin expression in 183 invasive carcinomas (100 ductal, 42 lobular, 41 with mixed ductal and lobular features) and 198 in situ carcinomas (131 ductal, 53 lobular, 14 in situ with ductal and lobular features) by immunohistochemistry. We found a highly significant correlation of E-cadherin membrane expression with the histologic phenotype of the tumors. While moderate to strong membrane expression of E-cadherin was seen in all invasive and in situ ductal carcinomas, 41 of 42 invasive and 50 of 53 in situ lobular carcinomas showed complete loss of expression. All in situ carcinomas diagnosed histologically as showing mixed ductal and lobular features demonstrated complete loss of staining. Invasive carcinomas with ductal and lobular features showed 3 staining patterns: (1) complete or almost complete lack of membrane staining similar to that seen in lobular carcinomas, (2) uniform membrane expression throughout the tumor similar to ductal carcinomas, and (3) focal loss of E-cadherin staining, which correlated well with the histologic impression of focal lobular features. In tumors with histologically equivocal features, immunohistochemical detection of E-cadherin expression can be a useful diagnostic tool for the differentiation of ductal and lobular carcinomas of the breast.

Enzyme-linked immunoassay of pre-S gene-coded sequences in hepatitis B vaccines.

Pre-S gene coded domains of the hepatitis B virus (HBV) envelope protein are highly immunogenic in experimental animals and humans. Their presence in HBV and hepatitis B surface antigen (HBsAg) particles leads to production of anti-pre-S-specific antibodies during the course of HBV infection. Since antibodies specific for pre-S domains are capable of preventing the attachment of HBV to hepatocytes and are virus neutralizing, it would seem desirable to produce HBV vaccines with a standardized level of pre-S determinants to ensure their potential for eliciting the same repertoire of protective antibodies as found after recovery from natural infection. However, a test with appropriate sensitivity for detecting pre-S determinants to ensure their potential for eliciting the same repertoire of protective antibodies as found after (ELISA) for detecting pre-S determinants in vaccines containing less than or equal to 20 micrograms of HBsAg. The components of this assay are (1) antibodies to a synthetic peptide pre-S (120-145) adsorbed to polystyrene beads, and (2) beta-lactamase-labelled antibodies purified from anti-HBV serum on the basis of their affinity for a pre-S (120-174) beta-galactosidase fusion protein produced in Escherichia coli. Results of an evaluation of the pre-S content of HBV vaccines from two different commercial sources are discussed.

Self-insured employer health plans: prevalence, profile, provisions, and premiums.

Data from three recent surveys indicate that about 40 percent of workers with employment-based health insurance are enrolled in plans that their employers self-insure. Despite the considerable differences between federal regulation of these self-insured plans and state regulation of employer plans purchased from an insurance company, we find striking similarities in the populations they serve, the benefits they offer, and their premium costs. Implications for health policy are discussed.

A novel agonist, phorbol 12-phenylacetate 13-acetate 20-homovanillate, abolishes positive cooperativity of binding by the vanilloid receptor.

Capsaicin binds to a specific recognition site, referred to as the vanilloid receptor, which it shares with the natural, ultrapotent agonist resiniferatoxin and with the competitive antagonist capsazepine. Upon binding to its receptor, capsaicin opens a cation channel leading to Ca2+ influx. The binding of capsaicin or resiniferatoxin by the vanilloid receptor follows a sigmoidal saturation curve, indicative of positive cooperativity. The biological significance of this positive cooperative behaviour is unknown, as is the mechanism responsible for it. We have developed a novel ligand, phorbol 12-phenylacetate 13-acetate 20-homovanillate (PPAHV), which binds to cultured rat sensory neurons (with a Ki of 3.1 +/- 0.4 microM), and induces Ca2+ uptake by them (with an ED50 of 1.8 +/- 0.3 microM) with similar affinities and in a non-cooperative manner (Hill coefficients are 0.99 and 1.06 for binding and Ca2+ uptake, respectively). The behaviour of PPAHV thus contrasts with resiniferatoxin or capsaicin not only in the lack of cooperativity but also in the relative potencies for resiniferatoxin binding versus Ca2+ uptake (resiniferatoxin is less potent and capsaicin is more potent for induction of Ca2+ uptake than for binding). In further experiments in which the concentration of [3H]resiniferatoxin was varied, 1 microM PPAHV likewise reduced the cooperativity index that characterizes resiniferatoxin binding to rat spinal cord membranes from 2.3 +/- 0.1 to 1.1 +/- 0.2; in parallel experiments, neither capsaicin nor capsazepine (both at a concentration of 2 microM) affected binding cooperativity. Moreover, PPAHV (1 microM) turned the bi-phasic dissociation curve of resiniferatoxin into a monophasic curve, eliminating the second, slow-dissociation phase. The present results suggest that positive cooperativity is a ligand-induced feature rather than an inherent property of vanilloid receptors. A comparison of the spectrum of biological activity of ligands which bind to vanilloid receptors with different degrees of cooperativity may provide an approach to explore the functional significance of this binding behaviour.

Comparison of [3H]resiniferatoxin binding to spinal cord and dorsal root ganglia of newborn and adult rats.

Capsaicin is frequently used in neurobiological investigations to selectively inhibit response by the primary sensory afferent neurons. The effectiveness of treatment depends significantly on the age of the animals; newborns are both quantitatively and qualitatively more sensitive than adults. In the present study, we used the [3H]resiniferatoxin binding assay to determine whether this different susceptibility to capsaicin between newborns and adult animals may reflect differences either in receptor affinity or density. We report here that whole spinal cord membranes of neonates bound [3H]RTX with similar affinity and positive cooperativity as did the spinal cord membranes from adult animals (Kd values were 24.8 +/- 3.7 and 26.8 +/- 4.8 pM, respectively; Hill coefficients were 2.25 +/- 0.03 and 2.17 +/- 0.05, respectively). However, the receptor density was three-fold higher in the spinal cord membranes of neonates than of adult rats (Bmax values were 142 +/- 13 and 43 +/- 3 fmol/mg protein, respectively). We found no significant difference in the [3H]RTX binding properties of dorsal root ganglia membranes of newborn and adult animals. Our results suggest that a higher density of the vanilloid receptor in the spinal cord (but not in the dorsal root ganglia) of newborn animals may contribute to the quantitative differences between the sensitivity of adult animals and neonates.

[3H]resiniferatoxin binding to pig dorsal horn membranes displays positive cooperativity.

In the present report we have reevaluated specific [3H]resiniferatoxin (RTX) binding, thought to represent the vanilloid (capsaicin) receptor, to whole spinal cord and dorsal horn membranes of the pig using a modified [3H]RTX binding assay. The high nonspecific [3H]RTX binding of the original protocol was reduced by the addition of alpha 1-acid glycoprotein (AGP), a plasma protein that binds RTX, to the assay mixture after the binding reaction had been terminated. Specific [3H]RTX binding to pig whole spinal cord and dorsal horn membranes followed sigmoidal saturation kinetics indicating apparent positive cooperativity. The cooperativity index determined by fitting the data to the Hill equation was 2.31 +/- 0.24 in the spinal cord and 2.27 +/- 0.13 in the dorsal horn. The apparent dissociation constants in spinal cord and dorsal horn membranes were 87.8 +/- 2.7 and 103.9 +/- 1.9 pM; the receptor densities were 23 +/- 3 and 203 +/- 5 fmol/mg protein, respectively. In parallel experiments, rat spinal cord membranes bound [3H]RTX with 2 - 3 fold higher affinity, equal positive cooperativity, and a 49 +/- 6 fmol/mg receptor density. As predicted by the modified Hill equation, at low receptor occupancy nonradioactive RTX produced biphasic competition curves. Capsaicin and the competitive antagonist capsazepine also fully displaced specifically bound [3H]RTX from pig dorsal horn membranes with Ki values of 9.7 +/- 1.7 microM and 6.8 +/- 0.7 microM, respectively; the corresponding Hill coefficients were 1.81 +/- 0.17 and 2.32 +/- 0.11. [3H]RTX binding was not inhibited by resiniferonol 9, 13, 14-orthophenylacetate, the biologically inactive parent diterpene of RTX. These findings suggest that the vanilloid receptor present in the dorsal horn of the pig, like those present in human and in the rat, is a receptor cluster in which the subunits cooperate.

Comparison of [3H]resiniferatoxin binding by the vanilloid (capsaicin) receptor in dorsal root ganglia, spinal cord, dorsal vagal complex, sciatic and vagal nerve and urinary bladder of the rat.

In the present report we compared the properties of [3H]resiniferatoxin (RTX) binding by the vanilloid receptors present at different parts of the primary afferent neurons of the rat. We found no major differences in either the affinity or the cooperativity of [3H]RTX binding by vanilloid receptors on the cell body, central terminals, peripheral terminals or axons. Specific binding of [3H]RTX to dorsal root ganglia, whole spinal cord, dorsal vagal complex, urinary bladder, and sciatic and vagal nerves all followed sigmoidal saturation kinetics indicating positive cooperativity among the binding sites. The cooperativity indexes determined by fitting the data to the Hill equation were 1.82 +/- 0.11, 2.21 +/- 0.04, 2.55 +/- 0.01, 1.91 +/- 0.11, 2.03 +/- 0.09 and 2.27 +/- 0.04, respectively. The dissociation constants in dorsal root ganglia, spinal cord, dorsal vagal complex, urinary bladder, and sciatic and vagal nerve membranes were 46.5 +/- 2.7, 29.3 +/- 5.1, 28.2 +/- 1.2, 60.8 +/- 4.4, 59.9 +/- 1.9 and 45.2 +/- 0.7 pM; the receptor densities were 219 +/- 14, 48 +/- 5, 67 +/- 1, 32 +/- 7, 61 +/- 9, and 100 +/- 20 fmol/mg protein, respectively. We could not show any major differences in the affinities of capsaicin and capsazepine in inhibition of [3H]RTX binding by the different membrane preparations either. In all cases the initial enhancement of [3H]RTX binding by nonradioactive RTX, capsaicin, and capsazepine confirmed the existence of positive cooperativity among the binding sites. We were unable to detect specific [3H]RTX binding sites in membrane preparations of the preoptic area, locus ceruleus, substantia nigra, striatum and paraventricular nuclei of the rat brain under our present conditions. Our results suggest the uniformity of the vanilloid receptors present at different parts of the primary afferent neuron.