Ion-Selective Electrodes for Measuring Potassium in Erythrocytes: a Model for Clinical Interpretation of the Results (a Pilot Study).

The aim of the investigation is to study the concentration of potassium in erythrocytes using the proposed method, potassium interconnection with other electrolyte and acid-base parameters of blood plasma, and to create the basis for clinical interpretation of the results. Materials and Methods: Potassium content in erythrocytes was measured using a blood gas analyzer with ion-selective electrodes in parallel with the laboratory procedure. Patients from intensive care units were randomly selected for the study. Results: No correlations of potassium with other plasma parameters have been found, however its buffer dependence on chlorine in plasma has been established. Minimal value of potassium concentration in erythrocytes (for 356 measurements) was 68.2 mmol/L, maximal - 210.2 mmol/L.Following the logic of the acid-base status, a nomogram for clinical interpretation of intracellular potassium homeostasis has been developed. The low values are mainly connected with the deficit of potassium which is impossible to determine in blood plasma (e.g. in severe metabolic alkalosis or diuretic therapy). The elevated concentration of potassium in erythrocytes is caused by eryptosis: released potassium is absorbed by normal erythrocytes (protection from hyperkalaemia). So, the increased concentration of potassium indicates directly the presence of eryptosis triggers, i.e. inflammatory mediators, oxidative stress, and others, for example in sepsis. The results of the study have shown that measurement of potassium concentration in erythrocytes with the help of ion-selective electrodes is an effective method of monitoring its intracellular homeostasis. Potassium in erythrocytes is an independent biological marker which can provide clinically relevant information.

Effectiveness of acupuncture for treatment of childhood constipation.

The aim of the present study was to examine the influence of acupuncture on chronic constipation in children and to investigate their basal plasma panopioid level and the changes of this treatment. Seventeen children constipated for at least six months were treated by five weekly placebo acupuncture sessions, followed by 10 weekly true acupuncture sessions. Their parents filled a bowel habit questionnaire. Panopioid activity was measured at time 0 and after 5, 10, and 15 acupuncture sessions. The frequency of bowel movements in males increased more gradually compared to females and reached a maximal improvement only after 10 true acupuncture sessions, from 1.4 +/- 0.6/week to 4.4 +/- 0.6/week and females from 1.4 +/- 0.3/week up to 5.6 +/- 1.2/week. The basal panopioid activity was lower in constipated children as compared to the control population and increased gradually up to control level after 10 true acupuncture sessions. This study is the first to describe a successful treatment by acupuncture of constipated children.

Seroprevalence and determinants of diphtheria, tetanus and poliomyelitis antibodies among adults in Berlin, Germany.

The immunity levels against diphtheria, tetanus and poliomyelitis were investigated among blood donors (n = 2079) in Berlin. Of all participants, only 60% had full, long-term protection against diphtheria, 72% against tetanus, 87% against poliomyelitis type 1, 77% against poliomyelitis type 2 and 73% against type 3. There was a striking decrease of tetanus and diphtheria immunity levels by age. Immunity levels against tetanus were higher among males, whereas females were better protected against poliomyelitis. After adjusting for confounding effects in logistic regression diphtheria immunity in those aged <40 years was significantly higher in participants from East-Berlin, whereas the immunity levels against poliomyelitis were higher in West-Berlin. These differences reflect the different vaccination policies in East-Germany and West-Germany before 1989. There is a need to improve the immunity levels of the adult population in Berlin.

The effects of angiotensin II, endothelin-1, and protein kinase C inhibitor on DNA synthesis and intracellular calcium mobilization in vascular smooth muscle cells from young normotensive and spontaneously hypertensive rats.

Angiotensin II (Ang-II) and endothelin 1 (ET-1) are important peptides that induce a prolonged vasoconstriction and enhance proliferation of vascular smooth muscle cells (VSMC). These substances may have an important role in the development of hypertension and atherosclerosis. Our objectives were to determine whether there are inborn differences in the proliferation patterns of VSMC obtained from spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY) by studying the effects of Ang-II and ET-1 on VSMC from those strains before the onset of hypertension, and to evaluate the roles of protein kinase C (PKC) and intracellular Ca2+ in the mechanism of action of ET-1 and Ang-II. VSMC from aortas of young (1- to 2-week-old) SHR and WKY rats were grown as primary cultures in plates for 48 h. The cells were incubated with Ang-II (0.1 to 1000 nmol/L) or ET-1 (0.1 to 100 nmol/L). VSMC were also incubated in the presence of various concentrations of a PKC inhibitor, chelerythrine (0.1-10 nmol/L). Thymidine incorporation into DNA was measured as an indicator of DNA synthesis. Intracellular free Ca2+ was determined by using FURA-2AM. ET-1 and Ang-II caused a marked dose-dependent enhancement of thymidine incorporation into DNA. The responses of VSMC from WKY and SHR to Ang-II and ET-1 were similar. In both strains, chelerythrine caused a dose-dependent suppression in the activity of ET-1 and Ang-II. However, VSMC from SHR incubated in the presence of ET-1 were more susceptible to the inhibitory effect of chelerythrine. Both Ang-II and ET-1 induced an increase of intracellular free Ca2+. ET-1 induced a larger increase than Ang-II (190% and 100% greater than baseline free Ca2+ levels, respectively), in spite of a lower concentration of ET-1 (ET-1 = 30 nmol/L; Ang-II = 100 nmol/L). Ang-II and ET-1 exerted a similar mitogenic effect on primary cultures of VSMC obtained from young SHR before the development of hypertension, compared with WKY. The mitogenic activity of Ang-II and ET-1 was accompanied by an increase of intracellular free Ca2+. The effect of ET-1 upon intracellular Ca2+ was stronger than that of Ang-II. VSMC cultures of SHR stimulated with ET-1 were more susceptible to PKC inhibition than those of WKY. The similarity of the effects of Ang- II and ET-1 on SHR and WKY does not exclude their role in the pathogenesis of hypertension and atherosclerosis, and further studies should be carried out to determine their role.

Pre- and postsynaptic alterations in the septohippocampal cholinergic innervations after prenatal exposure to drugs.

The present study was designed to evaluate possible presynaptic and postsynaptic alterations in the hippocampal cholinergic innervations that account for the hippocampus-related behavioral deficits found after prenatal drug exposure. Mice were prenatally exposed to either phenobarbital or heroin. On postnatal day 50, the hippocampi were removed and protein kinase C (PkC) activity, the amounts of Gi, Go, and Gq guanosine 5'-triphosphate binding proteins (G-proteins), and choline transports were determined. Basal PkC activity was higher than control levels in both phenobarbital and heroin treated mice, by 41% and 35%, respectively. The increase of PkC activity in response to carbachol was impaired in both treatment groups: in control mice, membrane PkC activity in hippocampal slices increased by 40%-50%, while no such response, or even slight reduction in PkC activity, was observed in the drug-exposed offspring. A significant increase was found in Gi and Gq G-proteins (18%-21%) in mice exposed to phenobarbital or to heroin compared with control levels. The amount of choline transporters, determined by hemicholinium binding, increased by 70% compared with the control level in mice prenatally exposed to heroin, and increased by 71% in mice prenatally exposed to phenobarbital. The alterations in basal and carbachol-stimulated hippocampal PkC activity after prenatal drug exposure may be related to an impairment in long-term potentiation (LTP); which plays an important role in hippocampal related behavioral abilities, changes in which are caused by prenatal drug exposure.

Opioid modulation of extracellular signal-regulated protein kinase activity is ras-dependent and involves Gbetagamma subunits.

Although it is well-established that G protein-coupled receptor signaling systems can network with those of tyrosine kinase receptors by several mechanisms, the point(s) of convergence of the two pathways remains largely undelineated, particularly for opioids. Here we demonstrate that opioid agonists modulate the activity of the extracellular signal-regulated protein kinase (ERK) in African green monkey kidney COS-7 cells transiently cotransfected with mu-, delta-, or kappa-opioid receptors and ERK1- or ERK2-containing plasmids. Recombinant proteins in transfected cells were characterized by binding assay or immunoblotting. On treatment with corresponding mu- ([D-Ala2,Me-Phe4,Gly-ol5]enkephalin)-, delta- ([D-Pen2,D-Pen5]enkephalin)-, or kappa- (U69593)-selective opioid agonists, a dose-dependent, rapid stimulation of ERK1 and ERK2 activity was observed. This activation was inhibited by specific antagonists, suggesting the involvement of opioid receptors. Pretreatment of cells with pertussis toxin abolished ERK1 and ERK2 activation by agonists. Cotransfection of cells with dominant negative mutant N17-Ras or with a betagamma scavenger, CD8- beta-adrenergic receptor kinase-C, suppressed opioid stimulation of ERK1 and ERK2. When epidermal growth factor was used to activate ERK1, chronic (>2-h) opioid agonist treatment resulted in attenuation of the stimulation by the growth factor. This inhibition was blocked by the corresponding antagonists and CD8- beta-adrenergic receptor kinase-C cotransfection. These results suggest a mechanism involving Ras and betagamma subunits of Gi/o proteins in opioid agonist activation of ERK1 and ERK2, as well as opioid modulation of epidermal growth factor-induced ERK activity.

Cannabinol derivatives: binding to cannabinoid receptors and inhibition of adenylylcyclase.

Several derivatives of cannabinol and the 1,1-dimethylheptyl homolog (DMH) of cannabinol were prepared and assayed for binding to the brain and the peripheral cannabinoid receptors (CB1 and CB2), as well as for activation of CB1- and CB2-mediated inhibition of adenylylcyclase. The DMH derivatives were much more potent than the pentyl (i.e., cannabinol) derivatives. 11-Hydroxycannabinol (4a) was found to bind potently to both CB1 and CB2 (Ki values of 38.0 +/- 7.2 and 26.6 +/- 5.5 nM, respectively) and to inhibit CB1-mediated adenylylcyclase with an EC50 of 58.1 +/- 6.2 nM but to cause only 20% inhibition of CB2-mediated adenylylcyclase at 10 microM. It behaves as a specific, though not potent, CB2 antagonist. 11-Hydroxycannabinol-DMH (4b) is a very potent agonist for both CB1 and CB2 (Ki values of 100 +/- 50 and 200 +/- 40 pM; EC50 of adenylylcyclase inhibition 56.2 +/- 4.2 and 207.5 +/- 27.8 pM, respectively).

Acupuncture and the opioid system: implications in management of migraine.

We investigated the effectiveness of acupuncture in childhood migraine in 22 children with migraine, randomly divided into two groups: a true acupuncture group (12 children) and a placebo acupuncture group (10 children). Ten healthy children served as a control group. Opioid activity in blood plasma was assayed by two methods: (1) determination of total (panopioid) activity with an opiate radioreceptor assay, and (2) determination of beta-endorphinlike immunoreactivity by radioimmunoassay. The true acupuncture treatment led to significant clinical reduction in both migraine frequency and intensity. At the beginning of the study, significantly greater panopioid activity was evident in plasma of the control group than in plasma of the migraine group. The true acupuncture group showed a gradual increase in the panopioid activity in plasma, which correlated with the clinical improvement. After the tenth treatment, the values of opioid activity of the true acupuncture group were similar to those of the control group, whereas the plasma of the placebo acupuncture group exhibited insignificant changes in plasma panopioid activity. In addition, a significant increase in beta-endorphin levels was observed in the migraine patients who were treated in the true acupuncture group as compared with the values before treatment or with the values of the placebo acupuncture group. The results suggest that acupuncture may be an effective treatment in children with migraine headaches and that it leads to an increase in activity of the opioidergic system.

[Study of 176 HIV-seropositive children in Santa Catarina State]. / Estudo de 176 crianças soropositivas para o HIV em Santa Catarina.

OBJECTIVE: The incidence of the acquired immunodeficiency syndrome (AIDS) has increased in Santa Catarina State in Brazil over the last years, with a high number of infected women and children. The purpose of this study was to establish the main characteristics of the children from this State whose HIV serologic tests were positive. METHODS: This was a descriptive study of 176 children with positive serologic tests to HIV, conducted in the Hospital Infantil Joana de Gusmão, Florianópolis City, Santa Catarina State, Brazil. RESULTS: Most of the children (105 cases, 59.6%) were born in Florianópolis, Capital of Santa Catarina State, and Itajaí (22 cases, 12.5%). Vertical transmission of HIV was observed in 167 patients (94.9%). Among 167 HIV-positive mothers, 77 (46.1%) of them acquired the virus by sexual transmission and 35 (21.0%) by use of injectable drugs. However, among 89 HIV-positive fathers, 63 (70.7%) of them used to take drugs. The average age of the HIV-positive children whose serologic tests became negative was 10.5 months. Among 103 symptomatic patients, 87 (84.5%) presented hepatomegaly, 81 (78.6%) lymphadenopathy, 66 (64.0%) splenomegaly, 59 (57.3%) skin bruises, 54 (52.4%) recurrent bronchopneumonia and 50 cases (48.5%) recurrent diarrhea. The most frequent opportunistic infection was mucocutaneous candidiasis that occurred in 41 children (39.8%). CONCLUSIONS: The characteristics were similar to those reported in the literature. A great concentration of HIV infected persons was observed in the coast area where there are three harbor towns, an elevated number of injectable drug users and presence of many tourists.

Distinct components of morphine effects on cardiac myocytes are mediated by the kappa and delta opioid receptors.

Morphine exerts direct effects on cultured cardiac myocytes from neonatal rats. These effects are mediated via the delta and the kappa opioid receptors, as mu opioid receptors are not present in neonatal cardiomyocyte cultures. Binding parameters to the delta and kappa opioid receptors were determined in membrane preparations from these cultures by heterologous competition to [3H]diprenorphine binding, with [D-Pen2, D-Pen5]-enkephalin (DPDPE) and trans-(dl)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate (U-50,488H) as specific displacers respectively. To define the components of morphine effects mediated via activation of either the delta or the kappa opioid receptor alone, cardiac myocytes were exposed to morphine in the presence of specific antagonists to the kappa or delta opioid receptor respectively. Activation of the kappa opioid receptors by morphine caused a transient increase in Ca2+ influx, leading to increase in amplitudes of [Ca2+]i transients and contraction, with no change in the intracellular pH. Activation of the delta opioid receptors alone by morphine caused a decrease in the amplitude of contraction. This decrease was mediated by a decrease in the intracellular pH leading to reduced responsiveness of the myofilaments to Ca2+. There was no change in Ca2+ influx and in the amplitude of [Ca2+]i transients. The effects mediated through the delta opioid but not through the kappa opioid receptors were pertussis toxin sensitive, indicating coupling of the delta opioid receptors to pertussis toxin sensitive GTP-binding proteins. The overall effects of morphine on the neonatal cardiac myocytes were the sum of the effects exerted by morphine when it activated each of the opioid receptors alone.

Muscarinic control of amyloid precursor protein secretion in rat cerebral cortex and cerebellum.

It was previously shown by us and by others that activation of muscarinic acetylcholine receptors evoke amyloid precursor protein (APP) secretion in various cell lines. Here we examined if such muscarinic control of APP secretion occurs also in normal brain tissues. We found that the secretion of APP from rat cerebrocortical slices (rich in M1 receptors) was significantly increased by K+ depolarization, the non-selective agonist, carbachol (CCh), and the M1-selective agonist, AF102B. CCh also increased APP secretion from cerebellar slices (rich in M2 receptors) while AF102B had no significant effect in this brain region. Despite of its stimulatory effect on APP release in the cerebellum, CCh had no effect on phosphoinositide (PI) metabolism in this brain region. In the cerebral cortex PI metabolism was significantly increased by CCh but only partially increased by AF102B. These results suggest that APP secretion in the brain is mediated via muscarinic receptors. In the cerebral cortex APP secretion seems to be regulated via M1 receptors. Our results also suggest that PI metabolism is not a pronounced step in mediating APP processing.

Inhibition of experimentally induced cirrhosis in rats by hypothyroidism.

The coexistence of hyperkinetic circulation, hypermetabolism, and hyperactivity of the sympathetic nervous system is encountered in both cirrhosis and hyperthyroidism. Several drugs, such as propylthiouracil and propranolol, that are beneficial for treating some patients with chronic liver diseases are also prescribed for the treatment of thyrotoxicosis. We investigated the effects of experimentally induced hypo- and hyperthyroidism on the development of cirrhosis induced in rats by thioacetamide (TAA). We specifically examined whether hypothyroidism could prevent and hyperthyroidism could aggravate liver damage. Hypothyroidism induced by methimazole (MMI, 0.04%), propylthiouracil (PTU 0.05%), and by thyroidectomy was confirmed by a significant elevation of thyroid-stimulating hormone (TSH) levels. Hyperthyroidism (decreased TSH levels) was induced by eltroxin (ELT:50 micrograms/kg). Thirteen groups of 10 rats each were studied: euthyroid controls (3 groups: water, TAA 1.5 months, and TAA 3 months), hypothyroid (6 groups: MMI, PTU, surgical, MMI-TAA, PTU-TAA, surgical-TAA), and hyperthyroid (4 groups:ELT 1.5 months and 3 months, and ELT-TAA for 1.5 months and 3 months). Hepatic fibrosis (scored from 0 to 3) was significantly reduced (P < .0001) in hypothyroid rats as compared with euthyroid controls, and was aggravated in TAA-treated hyperthyroid rats (P < .0001). Quantitative microscopic analysis of liver biopsy specimens from all groups confirmed the semiquantitative histopathological scores (P < .001). Direct intrasplenic pressure measurement revealed a significant portal pressure elevation in the TAA and the ELT-treated rats (from 4.7 +/- 0.1 in the euthyroid group to 8.1 +/- 2.3 and 10.2 +/- 2.1 and 12.5 +/- 1.6 in the TAA, ELT and ELT-TAA groups, respectively). However, in the hypothyroid-TAA groups, the portal pressure was found to be within the euthyroid normal range (4.6 +/- 1.2 and 5.8 +/- 0.6 in the PTU-TAA and surgical-TAA, respectively). After 12 weeks, the mean spleen weight of rats receiving only TAA was significantly higher than the TAA-treated hypothyroid rats (P < .0001), indicating that the hypothyroid TAA-treated rats were less portal hypertensive. These results suggest that induced hypothyroidism can inhibit, whereas hyperthyroidism can aggravate, the development of cirrhosis in a rat model.

Buprenorphine differentially alters opioid receptor adaptation in rat brain regions.

Previous in vivo studies revealed that the mixed agonist-antagonist buprenorphine can down-regulate mu and up-regulate delta 2 and kappa 1 opioid receptors in rat brain. In this report brain regional differences in opioid receptor adaptation were addressed. Rats received i.p. injections with buprenorphine (0.5-2.5 mg/kg) and were killed 20 h later. Membranes from 7 brain regions were analyzed for mu (3H-[D-Ala2,N-mephe4,Gly-ol5] enkephalin), kappa 1 (3H-U-69593), delta 1 (3H-[D-Pen2, D-Pen5] enkephalin) and delta 2 (3H-deltorphin II) receptor binding parameters. Buprenorphine induced down-regulation of mu receptors in frontal cortex, occipital cortex, thalamus, hippocampus, striatum and brain stem. Kd values for 3H-[D-Ala2,N-mephe4,Gly-ol5] enkephalin were unchanged from controls. Up-regulation of kappa 1 receptors was observed in frontal, parietal, occipital cortexes and striatum. Binding to delta 2 sites was elevated in frontal and parietal cortexes. Buprenorphine did not alter delta 1 binding in any of the regions examined. Changes in opioid receptor adaptation induced by buprenorphine were further supported by data from cross-linking of 125I-beta-endorphin to cortical membrane preparations. A reduction in a 60- to 65-kDa band was detected in frontal and occipital cortices in which binding assays revealed down-regulation of mu receptors. In parietal cortex neither the 60- to 65-kDa product nor Bmax changes were observed. These results indicate that buprenorphine is a useful tool to study brain opioid receptor adaptation in vivo and the information accrued may be relevant to the mode of action of this drug in the treatment of heroin and cocaine abuse.

Inhibition of experimentally-induced liver cirrhosis in rats by a nonpeptidic mimetic of the extracellular matrix-associated Arg-Gly-Asp epitope.

AIMS/METHODS: In the present study, we examined whether a nonpeptidic mimetic of Arg-Gly-Asp (RGD), which specifically inhibits RGD-dependent adhesion of CD4+ T lymphocytes or fibroblasts to fibronectin, can prevent thioacetamide-induced liver cirrhosis in rats. The nonpeptidic RGD mimetic, rather than the RGD peptide was utilized, since the peptide is rapidly degraded, and therefore, relatively ineffective for in vivo use. RESULTS: We now report that rats treated with thioacetamide and the RGD analogue SF-6,5 for 12 weeks had lower histopathologic scores than those treated with thioacetamide alone. Further improvement in liver histology was observed after another 8 weeks of treatment with the analogue SF-6,5. Quantitative microscopic analysis by computerized imaging morphometry of liver biopsies from the three groups and controls confirmed the semi-quantitative histopathologic scores (p < 0.001). After 3 months of treatment, the spleen weights in the SF-6,5-treated rats were 30% less than those of rats that received only thioacetamide, which indicated that the analogue-treated rats were less portal hypertensive. CONCLUSIONS: The observed inhibition of the progression of cirrhosis in rats by the nonpeptidic RGD analogue suggests that RGD mimetics may be useful therapeutically in inhibiting pathological processes that involve RGD recognition.

Correlation between secretagogue-induced Ca2+ influx, intracellular Ca2+ levels and secretion of catecholamines in cultured adrenal chromaffin cells.

Catecholamine secretion induced by various secretagogues in cultured bovine chromaffin cells has been correlated with Ca2+ influx and intracellular Ca2+ concentrations. Nicotine and high K+ caused prompt secretion of catecholamines from cells. Coincidently, both secretagogues evoked 45[Ca2+] influx with a parallel increase in free intracellular Ca2+ concentration, as determined by Quin 2 fluorescence. However, the rate of return of Ca2+ level to baseline after nicotine stimulation was more rapid than after K+ stimulation. In comparison, stimulation with veratridine produced a slow and prolonged Ca2+ influx accompanied by lower levels of intracellular Ca2+ than those observed after nicotine or K+ stimulation. Yet, during 15 min of stimulation, veratridine induced a substantial catecholamine release, which was larger than that obtained after nicotine or K+ stimulations. The Ca2+ ionophore A23187 (1 microM) induced a pronounced increase in intracellular Ca2+ levels, but did not evoke any significant catecholamine release. Finally, addition of the Ca2+ channel blocker verapamil following stimulation, at a time when intracellular Ca2+ concentration was at its peak level, did not affect the rate of decline in intracellular free Ca2+ concentration but promptly blocked Ca2+ uptake and catecholamine secretion. These findings suggest that the rate of Ca2+ influx, rather than the absolute level of intracellular Ca2+ concentration, determines the rate and extent of catecholamine release.

Identification of a tau promoter region mediating tissue-specific-regulated expression in PC12 cells.

Tau, a microtubule-associated protein, is encoded by a single gene, the expression of which is neuron-specific and developmentally regulated. When PC12 cells are exposed to nerve growth factor (NGF), they differentiate to sympathetic-like neurons. This differentiation process is accompanied by an elevation of tau proteins and mRNA. Here, we describe, for the first time, the isolation and characterization of a tau promoter region. We show that the promoter of tau is G + C-rich, lacks a genuine TATA box and thus promotes multiple initiation sites of RNA transcription. Our results demonstrate that a region of approximately 335 base-pairs residing immediately upstream of tau exon -1 are able to direct positive control of neuron-specific activity of the luciferase reporter gene. The isolation of tau promoter will facilitate facilitate further studies of the regulation of tau expression during development and aging of neuronal cells.

Expression of opioid receptors during heart ontogeny in normotensive and hypertensive rats.

BACKGROUND: The opioidergic systems are involved in modulating nociceptive stimuli. In addition, the recent results suggest that endogenous and exogenous opioids could play a role in the modulation of blood pressure and cardiac functions. However, little is known regarding the expression and role of opioid-binding sites in the heart. The decreased sensitivity to noxious stimuli in hypertensive rats raises the possibility of different developmental pattern expression of opioid-binding sites in normotensive versus hypertensive rats. METHODS AND RESULTS: Opioid receptor expression in hearts from hypertensive and normotensive rats was studied during heart development by binding assays. From P1 until P90, the development of the heart in the two rat strains was accompanied by a gradual increase in the density of kappa-opioid receptors. Hearts from hypertensive rats expressed significantly higher levels of kappa receptors compared with those of normotensive rats. At ages older than P7, mu-opioid receptors could not be detected in hearts of both strains, whereas delta-opioid-binding sites gradually increased until reaching adult levels. Seven-day-old cardiomyocyte cultures of both rat strains expressed similar densities of delta or kappa receptors to those observed in hearts from 7-day-old neonates. The mu-binding sites were not detected in cardiomyocytes cultures. Similar to the in vivo state, cultured myocytes from hypertensive rats had significantly higher levels of kappa-binding sites (1.5 fold) compared with those of normotensive rats. The kappa sites are pertussis toxin sensitive, and the state of coupling of the receptor to G protein is similar for the two rat strains. CONCLUSION: The role of opioid-binding sites in the heart is not completely clear. Hypertensive rats are known to be less sensitive to noxious stimuli compared with normotensive rats. It is controversial whether the site if application of noxious stimuli plays an important role in the sensitivity to pain in hypertensive rats. We suggest that the opioidergic system could play a role in the modulation of blood pressure in addition to its known effect on nociception.