Impact of socioeconomic factors on allergic diseases

Allergic and immunologic conditions, including asthma, food allergy, atopic dermatitis, and allergic rhinitis, are among the most common chronic conditions in children and adolescents that often last into adulthood. Although rare, inborn errors of immunity are life-altering and potentially fatal if unrecognized or untreated. Thus, allergic and immunologic conditions are both medical and public health issues that are profoundly affected by socioeconomic factors. Recently, studies have highlighted societal issues to evaluate factors at multiple levels that contribute to health inequities and the potential steps toward closing those gaps. Socioeconomic disparities can influence all aspects of care, including health care access and quality, diagnosis, management, education, and disease prevalence and outcomes. Ongoing research, engagement, and deliberate investment of resources by relevant stakeholders and advocacy approaches are needed to identify and address the impact of socioeconomics on health care disparities and outcomes among patients with allergic and immunologic diseases.

Associations between mitochondrial biomarkers, urban residential exposures and childhood asthma outcomes over 6 months

Determining biomarkers of responses to environmental exposures and evaluating whether they predict respiratory outcomes may help optimize environmental and medical approaches to childhood asthma. Relative mitochondrial (mt) DNA abundance and other potential mitochondrial indicators of oxidative stress may provide a sensitive metric of the child's shifting molecular responses to its changing environment. We leveraged two urban childhood cohorts (Environmental Control as Add-on Therapy in Childhood Asthma (ECATCh); Columbia Center for Children's Environmental Health (CCCEH)) to ascertain whether biomarkers in buccal mtDNA associate with airway inflammation and altered lung function over 6 months of time and capture biologic responses to multiple external stressors such as indoor allergens and fine particulate matter (PM2.5). Relative mtDNA content was amplified by qPCR and methylation of transfer RNA phenylalanine/rRNA 12S (TF/RNR1), cytochrome c oxidase (CO1), and carboxypeptidase O (CPO) was measured by pyrosequencing. Data on residential exposures and respiratory outcomes were harmonized between the two cohorts. Repeated measures and multiple regression models were utilized to assess relationships between mitochondrial biomarkers, respiratory outcomes, and residential exposures (PM2.5, allergens), adjusted for potential confounders and time-varying asthma. We found across the 6 month visits, a 0.64 fold higher level of TF/RNR1 methylation was detected among those with asthma in comparison to those without asthma ((parameter estimate (PE) 0.64, standard error 0.28, p = 0.03). In prospective analyses, CPO methylation was associated with subsequent reduced forced vital capacity (FVC; PE -0.03, standard error 0.01, p = 0.02). Bedroom dust mouse allergen, but not indoor PM2.5, was associated with higher methylation of TF/RNR1 (PE 0.015, standard error 0.006, p = 0.01). Select mtDNA measures in buccal cells may indicate children's responses to toxic environmental exposures and associate selectively with asthma and lung function.

Indoor Environmental Exposures and Their Relationship to Allergic Diseases

Cockroach, dust mite, cat, dog, mouse, and molds are major indoor allergens that have been associated with the development of allergic diseases and disease morbidity in allergen-sensitized individuals. Physical characteristics, such as allergen particle size, hydrophobicity, and charge, can determine an allergen's propensity to become airborne, location of respiratory tract penetration, and ability to elicit IgE responses in genetically predisposed individuals. Standardization and recent advancements in indoor allergen assessment serve to identify sources and distribution of allergens in a patient's home and public environment, inform public policy, and monitor the efficacy of allergen avoidance and therapeutics. Allergen exposure interventions have yielded mixed results with current US and international asthma guidelines differing on recommendations. A pragmatic, patient-centered approach to allergen avoidance includes: (1) tailoring intervention to the patient's sensitization and exposure status, (2) using a rigorous multifaceted intervention strategy to reduce allergen exposure as much as possible, and (3) beginning the intervention as soon as the patient is diagnosed. Further research into the risks/benefits of early allergen exposure, rapid and affordable in-home allergen assessment, and best practices for environmental control measures for asthma is needed.

Comprehensive home environmental intervention did not reduce allergen concentrations or controller medication requirements among children in Baltimore

OBJECTIVE

To determine if the addition of home environmental control strategies (ECSs) to controller medication titration reduces asthma controller medication requirements and in-home allergen concentrations among children with persistent asthma in Baltimore City.

METHODS

155 children ages 5-17 with allergen-sensitized asthma were enrolled in a 6-month randomized clinical trial of multifaceted, individually-tailored ECS plus asthma controller medication titration compared to controller medication titration alone. Participants had to meet criteria for persistent asthma and have had an exacerbation in the previous 18 months. Allergen sensitization (mouse, cockroach, cat, dog, dust mite) was assessed at baseline and home dust allergen concentrations were measured at baseline, 3 and 6 months. ECS was delivered 3-4 times over the trial. Asthma controller medication was titrated using a guidelines-based algorithm at baseline, 2, 4, and 6 months. The primary outcome was controller medication treatment step at 6 months (0-6, as-needed albuterol to high-dose ICS + LABA).

RESULTS

The population was predominately Black (90%), on public insurance (93%), and male (61%). The mean age was 10.1 years (SD 3.3). More than 70% were sensitized to a rodent, >50% to cockroach, and 70% were polysensitized. At 6 months, there were no differences in either treatment step (3.8 [SD 1.4] vs. 3.7 [SD 1.5]) or allergen concentrations between groups.

CONCLUSION

Among this predominantly low-income, Black pediatric asthma population, the addition of ECS to controller medication titration reduced neither indoor allergen concentrations nor controller medication requirements compared to controller medication titration alone.

Intergenerational transmission of the effects of maternal exposure to childhood maltreatment in the USA: a retrospective cohort study

BACKGROUND

Childhood maltreatment is associated with adverse health outcomes and this risk can be transmitted to the next generation. We aimed to investigate the association between exposure to maternal childhood maltreatment and common childhood physical and mental health problems, neurodevelopmental disorders, and related comorbidity patterns in offspring.

METHODS

We conducted a retrospective cohort study using data from the Environmental influences on Child Health Outcomes (ECHO) Program, which was launched to investigate the influence of early life exposures on child health and development in 69 cohorts across the USA. Eligible mother-child dyads were those with available data on maternal childhood maltreatment exposure and at least one child health outcome measure (autism spectrum disorder, attention-deficit hyperactivity disorder [ADHD], internalising problems, obesity, allergy, and asthma diagnoses). Maternal history of childhood maltreatment was obtained retrospectively from the Adverse Childhood Experiences or Life Stressor Checklist questionnaires. We derived the prevalence of the specified child health outcome measures in offspring across childhood and adolescence by harmonising caregiver reports and other relevant sources (such as medical records) across cohorts. Child internalising symptoms were assessed using the Child Behavior Checklist. Associations between maternal childhood maltreatment and childhood health outcomes were measured using a series of mixed-effects logistic regression models. Covariates included child sex (male or female), race, and ethnicity; maternal and paternal age; maternal education; combined annual household income; maternal diagnosis of depression, asthma, ADHD, allergy, or autism spectrum disorder; and maternal obesity. Two latent class analyses were conducted: to characterise patterns of comorbidity of child health outcomes; and to characterise patterns of co-occurrence of childhood maltreatment subtypes. We then investigated the association between latent class membership and maternal childhood maltreatment and child health outcomes, respectively.

FINDINGS

Our sample included 4337 mother-child dyads from 21 longitudinal cohorts (with data collection initiated between 1999 and 2016). Of 3954 mothers in the study, 1742 (44%) had experienced exposure to abuse or neglect during their childhood. After adjustment for confounding, mothers who experienced childhood maltreatment were more likely to have children with internalising problems in the clinical range (odds ratio [OR] 2·70 [95% CI 1·95-3·72], p<0·0001), autism spectrum disorder (1·70 [1·13-2·55], p=0·01), ADHD (2·09 [1·63-2·67], p<0·0001), and asthma (1·54 [1·34-1·77], p<0·0001). In female offspring, maternal childhood maltreatment was associated with a higher prevalence of obesity (1·69 [1·17-2·44], p=0·005). Children of mothers exposed to childhood maltreatment were more likely to exhibit a diagnostic pattern characterised by higher risk for multimorbidity. Exposure to multiple forms of maltreatment across all subtypes of maternal childhood maltreatment was associated with the highest risk increases for most offspring health outcomes, suggesting a dose-response relationship.

INTERPRETATION

Our findings suggest that maternal childhood maltreatment experiences can be a risk factor for disease susceptibility in offspring across a variety of outcomes and emphasise the need for policies focusing on breaking the intergenerational transmission of adversity.

FUNDING

Environmental influences on Child Health Outcomes Program, Office of the Director, National Institutes of Health.

The influence of urban exposures and residence on childhood asthma

Children with asthma who live in urban neighborhoods experience a disproportionately high asthma burden, with increased incident asthma and increased asthma symptoms, exacerbations, and acute visits and hospitalizations for asthma. There are multiple urban exposures that contribute to pediatric asthma morbidity, including exposure to pest allergens, mold, endotoxin, and indoor and outdoor air pollution. Children living in urban neighborhoods also experience inequities in social determinants of health, such as increased poverty, substandard housing quality, increased rates of obesity, and increased chronic stress. These disparities then in turn can increase the risk of urban exposures and compound asthma morbidity as poor housing repair is a risk factor for pest infestation and mold exposure and poverty is a risk factor for exposure to air pollution. Environmental interventions to reduce in-home allergen concentrations have yielded inconsistent results. Population-level interventions including smoking bans in public places and legislation to decrease traffic-related air pollution have been successful at reducing asthma morbidity and improving lung function growth. Given the interface and synergy between urban exposures and social determinants of health, it is likely population and community-level changes will be needed to decrease the excess asthma burden in children living in urban neighborhoods.

N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropanamides: KATP potassium channel openers. Modifications on the western region

A subset of antiandrogen compounds, the N-aryl-3,3,3-trifluoro-2-hydroxy-2-methylpropanamides 1, were found to activate ATP sensitive potassium channels (KATP) and represent a new class of potassium channel openers (PCOs). A structure-activity relationship was carried out on the western region of this series with the goal of obtaining an activator of the ATP sensitive potassium channel suitable for use in the treatment of urge urinary incontinence. In particular three large 4-(N-aryl) substituents, the (N-phenyl-N-methylamino)sulfonyl, benzoyl, and 4-pyridylsulfonyl moieties, yielded non-antiandrogen, KATP potassium channel openers (39, 41, and 64, respectively) that are bladder selective in an in vivo rat model that simultaneously measures bladder contractions, heart rate, and blood pressure. Substitutions of the aryl rings of 41 and 64 gave several derivatives that also display selectivity in the in vivo rat model; however, none appear to offer a substantial advantage over 41 and 64. The PCO activity of 41 and 64 resides in the (S)-(-) enantiomers. ZD6169, 41(S), has been selected into development for the treatment of urge urinary incontinence.

Telesurgery. Acceptability of compressed video for remote surgical proctoring

OBJECTIVE

To determine the clinical acceptability of various levels of video compression for remote proctoring of laparoscopic surgical procedures.

DESIGN

Observational, controlled study.

SETTING

Community-based teaching hospital.

PARTICIPANTS

Physician and nurse observers.

INTERVENTIONS

Controlled surgical video scenes were subjected to various levels of data compression for digital transmission and display and shown to participant observers.

MAIN OUTCOME MEASURES

Clinical acceptability of video scenes after application of video compression.

RESULTS

Clinically acceptable video compression was achieved with a 1.25-megabit/second data rate, with the use of odd-screen 43.3:1 Joint Photographic Expert Group compression and a small screen for remote viewing.

CONCLUSION

With proper video compression, remote proctoring of laparoscopic procedures may be performed with standard 1.5-megabit/second telecommunication data lines and services.

The acid metabolite of ZD7114 is a partial agonist of lipolysis mediated by the rat beta 3-adrenoceptor

Experiments were performed to characterise the lipolytic effects of the acid metabolite, ZM215001, ((S)-4-[2-hydroxy-3-phenoxy-propylamino-ethoxy] phenoxyacetic acid) of the putative beta 3-adrenoceptor agonist, ZD7114 ((S)-4-[2-hydroxy-3-phenoxy-propylamino-ethoxy]-N-(2-methoxyethyl) phenoxyacetamide) on isolated rat white adipocytes. ZM215001 was used for these studies since it is the predominant moiety after in vivo administration of ZD7114. The agonist properties of ZM215001 were assessed in comparison to the standard nonselective beta-adrenoceptor agonist (+/-)-isoprenaline and the beta 3-adrenoceptor-selective agonist BRL 37344. Isoprenaline, BRL 37344 and ZM215001 all stimulated the rate of free fatty acid release from isolated adipocytes with the order of potency being BRL > isoprenaline > ZM215001. The maximum effect of BRL 37344 was equivalent to that of isoprenaline, but ZM215001 achieved only 30% of the maximum isoprenaline response. ZM215001 competitively antagonised the lipolytic response to BRL 37344 (pA2 = 7.26), whereas the agonist effects of BRL 37344 were not antagonised competitively by the selective antagonists ICI 118551 and CGP 20712A, at concentrations which would be expected to block beta 1- and beta 2-adrenoceptors respectively. These results indicate that ZM215001 has low intrinsic activity at the rat adipocyte beta 3-adrenoceptor, and is a partial agonist of lipolysis in rat white adipocytes.

Effects of K+ channel blockers and cromakalim (BRL 34915) on the mechanical activity of guinea pig detrusor smooth muscle

There is strong evidence that cromakalim (BRL 34915) relaxes smooth muscle by opening cell membrane K+ channels. The aim of this study was to use relatively selective K+ channel blockers to investigate 1) the K+ channel type(s) opened by cromakalim in guinea pig detrusor and 2) the role of different K+ channel types in the control of basal tension. Cromakalim produced a concentration-related relaxation (IC50 = 0.50 +/- 0.03 microM, n = 42) of 15 mM K(+)-evoked mechanical activity. The ATP-sensitive K+ channel blocker glyburide (0.3-3 microM) antagonized the effects of cromakalim in an apparently competitive manner (pA2 = 6.76). Charybdotoxin and iberiatoxin (3-30 nM), blockers of the large conductance, Ca(++)-activated K+ channel, appeared to functionally antagonize cromakalim. Apamin (1 microM) and leiurotoxin I (0.3 microM), blockers of the small conductance, Ca(++)-activated K+ channel, and noxiustoxin (0.3 microM), a blocker of squid axon delayed rectifer K+ channels, all failed to antagonize cromakalim. Cumulative administration of charybdotoxin and iberiatoxin produced marked, concentration-related stimulation of mechanical activity per se whereas glyburide, noxiustoxin, apamin and leiurotoxin I had no effect. Apamin and leiurotoxin I did stimulate mechanical activity to a small extent when administered noncumulatively, however. The results suggest that cromakalim opens ATP-sensitive K+ channels in detrusor and suggest that cromakalim does not open CA(++)-activated K+ channels and noxiustoxin-sensitive, delayed rectifier K+ channels. The marked stimulatory effects of charybdotoxin and iberiatoxin per se suggest an important role for large conductance, Ca(++)-activated K+ channels in the control of basal tension and, presumably, membrane potential in detrusor smooth muscle cells.

Comparison of the effects of the K(+)-channel openers cromakalim and minoxidil sulphate on vascular smooth muscle

1 The actions of the potassium channel openers, cromakalim and minoxidil sulphate, were compared in a range of isolated blood vessel preparations. 2 Cromakalim and minoxidil sulphate inhibited spontaneous mechanical activity of the guinea-pig portal vein and relaxed the noradrenaline precontracted rat aorta with similar potency. In contrast, minoxidil sulphate was less potent than cromakalim in inhibiting spontaneous activity in the rat portal vein and was essentially inactive in the noradrenaline precontracted rat mesenteric artery and rabbit aorta. 3 Minoxidil sulphate did not antagonize the effects of cromakalim in the rabbit aorta indicating it was not acting as a partial 'agonist'. 4 Charybdotoxin, noxiustoxin and rubidium failed to discriminate between cromakalim and minoxidil sulphate indicating that the apparently selective effects of minoxidil sulphate were not mediated by either Ca(2+)-activated potassium channels, delayed rectifiers or rubidium impermeable potassium channels. 5 Glibenclamide antagonized the effects of cromakalim in an apparently competitive manner whereas the effects of minoxidil sulphate were antagonized in a non-competitive manner. The involvement of subtypes of ATP-sensitive potassium channels is discussed.

Interactions between angiotensin II and alpha-adrenoceptor agonists mediating pressor responses in the pithed rat

1. The aim of the study was to investigate the interactions between angiotensin II (AII) and adrenoceptor-mediated pressor responses in the pithed rat. Emphasis was placed on the effects of AII on blood pressure per se and the possibility of differential effects on alpha 1- and alpha 2-adrenoceptor-mediated pressor responses. 2. A low concentration of the angiotensin converting enzyme (ACE) inhibitor, teprotide (1 mg kg-1) lowered the resting diastolic blood pressure (BP) and attenuated only the second phase components of pressor responses to both alpha 1- and alpha 2-adrenoceptor agonists. Infusion of AII (50 ng kg-1 min-1) did not reverse the attenuating effect of teprotide and did not reliably restore the basal diastolic BP. 3. Although teprotide (10 mg kg-1) did not produce a greater fall in diastolic BP than did the low dose (1 mg kg-1), it attenuated the peak and second phase pressor responses to alpha 1- and alpha 2-adrenoceptor agonists but had no effect on pressor responses to AII or 5-hydroxytryptamine (5-HT). Infusion of AII reversed the effects of teprotide (10 mg kg-1) provided that rats were pretreated with flurbiprofen (5 mg kg-1), confirming that the depressor effects of the higher dose of teprotide are AII-dependent but that demonstration of this was complicated by products of cyclo-oxygenase. 4. The AII-receptor antagonist, saralasin (4 micrograms kg-1 min-1) attenuated alpha 1- and alpha 2-adrenoceptor-mediated pressor responses in a manner similar to that of teprotide (10 mg kg-1), suggesting that in this pithed rat model the alpha-adrenoceptor-mediated responses were selectively facilitated by endogenous AII. 5. Infusion of AII (50 ng kg-1 min-1) over a 60 min period did not produce a pressor response in the absence of other drugs but did facilitate pressor responses to alpha-adrenoceptor agonists. This confirms that AII can modulate alpha-adrenoceptor-mediated responses independently of basal blood pressure. 6. Overall the results indicate a facilitatory role for endogenous AII on alpha-adrenoceptor-mediated pressor responses. This is discussed in relation to the failure to demonstrate this convincingly under similar conditions on sympathetic nerve-mediated pressor responses.

Interactions between angiotensin II, sympathetic nerve-mediated pressor response and cyclo-oxygenase products in the pithed rat

1. The influence of angiotensin II (AII) on resting blood pressure and on sympathetic nerve-mediated pressor responses in the pithed rat was investigated either by inhibiting the renin-angiotensin system or by infusing AII. 2. Plasma AII levels in the pithed rat were approximately 20 fold higher than in normotensive rats. 3. Infusion of a subpressor dose of AII (50 ng kg-1 min-1) had no effect on sympathetic nerve mediated pressor responses but a pressor dose of AII, (200 ng kg-1 min-1) facilitated nerve-mediated pressor responses. 4. The angiotensin converting enzyme inhibitor, teprotide, and the AII-receptor antagonist, saralasin, lowered the diastolic blood pressure and attenuated sympathetic nerve-mediated pressor responses. There was no difference in the effects of teprotide at 1 mg kg-1 and 10 mg kg-1. Infusion of sodium nitroprusside at concentrations producing a fall in diastolic blood pressure of similar magnitude to that produced by teprotide and saralasin significantly attenuated nerve-mediated pressor responses. 5. After teprotide, AII 50 mg kg-1 min-1 increased diastolic blood pressure. The inhibitory effect of teprotide on nerve-mediated pressor responses was antagonized by this infusion of AII only if the rats were pretreated with the cyclo-oxygenase inhibitor, flurbiprofen. 6. It is concluded that AII is a major determinant of vascular tone in the pithed rat and that inhibition of the renin-angiotensin system attenuates sympathetic nerve-mediated pressor responses at least in part through the fall in blood pressure per se. The demonstration of this is complicated by an excessive release of vasodilator prostaglandins possibly due to the infused AII. Since plasma All levels are high, the effects of blockade of the renin-angiotensin system will be exaggerated and so the importance of All as a modulator of sympathetic responses will be overestimated in this model.

The effects of arterial blood gas tensions on pressor responses to angiotensin II in the pithed rat

The influence of arterial blood gas tensions on angiotensin II-mediated pressor responses in the pithed rat was studied by altering the inspired gas mixture at a fixed tidal volume. When rats were ventilated to produce physiological Pa, CO2 levels (35-40 mmHg) responses to boluses of angiotensin II were greater with increasing Pa, O2 over the Pa, O2 range of 65-460 mmHg. There was no difference in response to angiotensin II over the Pa, CO2 range studied (18-50 mmHg). All variations in response to angiotensin II were attributable to changes in Pa, O2. Since arterial blood gas tensions, especially the Pa, O2, modulate pressor responses to boluses of angiotensin II, the physiological effects of this hormone may be most fruitfully explored in rats ventilated to produce normal arterial blood gas tensions.

Analysis of the alpha-adrenoceptor-mediated, and other, components in the sympathetic vasopressor responses of the pithed rat

The vascular receptors activated following sympatho-adrenal stimulation were determined by analysing the effects of 'selective' antagonists on the vasopressor response to spinal sympathetic nerve activation in the pithed rat. The net vascular response to adrenal stimulation was a balance between alpha-adrenoceptor-mediated vasoconstriction and beta-adrenoceptor-mediated vasodepression. Part of the alpha-adrenoceptor-mediated response was 'prazosin-sensitive' (alpha 1) and the remainder was abolished by rauwolscine (alpha 2). As with adrenal stimulation, direct sympathetic nerve stimulation of the vasculature evoked pressor responses which were partly resistant to prazosin. Rauwolscine only partly blocked the prazosin-sensitive component. Reserpine pretreatment led to smaller responses than prazosin plus rauwolscine. Thus, the response resistant to alpha-adrenoceptor antagonists could be mediated, in part, by adrenoceptors distinct from alpha-adrenoceptors, as currently defined. alpha, beta-Methylene ATP reduced the nerve-mediated pressor response after alpha-adrenoceptor blockade or reserpine pretreatment but not in drug-free controls. The results suggest that stimulation of the adrenal medulla can produce a vasopressor response which consists of summating alpha 1- and alpha 2-adrenoceptor-mediated components, and is identical to the effect of injected adrenaline. In contrast, the response to vasopressor nerve stimulation appears to be essentially mediated by alpha 1-adrenoceptors, with a facilitatory influence from alpha 2-adrenoceptors. A further response obtained after alpha-adrenoceptor blockade may contain a purinergic component and another which is adrenergic but not mediated by stimulation of alpha-adrenoceptors.

The influence of blood gases on alpha 1- and alpha 2- adrenoceptor-mediated pressor responses in the pithed rat

The influence of blood gases on alpha 1- and alpha 2-adrenoceptor-mediated pressor responses was studied in the pithed rat by varying the inspired gas mixture or the ventilation stroke volume. Acidosis favoured the peak responses to the alpha 2-adrenoceptor agonist, xylazine, while alkalosis favoured the peak responses to the alpha 1-adrenoceptor agonist, phenylephrine. A combination of hypoxia and hypercapnia greatly depressed the alpha 1 response to phenylephrine whereas the alpha 2 response to xylazine remained relatively unaffected. When Pao2 was varied in either acidotic or alkalotic conditions the response to the phenylephrine increased as Pao2 increased. To prevent hypoxia in air ventilated rats, large stroke volumes were required. This caused alkalosis and hence decreased responsiveness to xylazine. Consequently, air ventilated pithed rats gave poorer responses to xylazine than did those ventilated on 100% O2. The results show that alpha 1- and alpha 2-adrenoceptor-mediated pressor responses can be differentially affected by blood gases. The relative contribution of alpha 1- and alpha 2-adrenoceptors to vascular tone may be either under- or over-estimated depending on the arterial blood gases.

Attempts to uncover subtypes of alpha-adrenoceptors and associated mechanisms by using sequential administration of blocking drugs

By the sequential administration of alpha 1- and alpha 2-blockers it can be shown, in the pithed rabbit, that the dose/pressor response curve to noradrenaline consists of two separate curves, one for each receptor. alpha 2-mediated responses predominate at low doses and alpha 1-mediated responses predominate at high doses. Pressor responses to sympathetic nerve stimulation have, similarly, an alpha 2 component at low frequencies and a dominant alpha 1-mediated response at high frequencies: a residual response is resistant to combined alpha 1- plus alpha 2-blockade. This alpha-blocker-resistant pressor nerve response was further analysed in the pithed rat and was found to be partly susceptible to alpha,beta-methylene ATP, which desensitizes purinergic responses. However, reserpine pretreatment produced a greater reduction of nerve-mediated pressor responses than did alpha-blockade, suggesting that part of the 'alpha-blocker resistant' response might be adrenergic. It is concluded that sympathetic vasopressor nerve transmission is mediated for the greater part by alpha 1- and alpha 2-adrenoceptors but that there is evidence for contributions from non-alpha-adrenergic and 'purinergic' elements. An even greater proportion of the responses to circulating catecholamines is attributable to the alpha-receptors with a relatively small but significant 'resistant' component.

Influence of blood gases, Ca2+-entry blockade and angiotensin converting enzyme inhibition on pressor responses to alpha-adrenoceptor agonists: evidence in vivo for subtypes of response independent of receptor subtype?

The pressor responses in the pithed rat to alpha-adrenoceptor agonists can be modified by alterations in arterial blood gas levels or by drugs which interfere with excitation-contraction coupling processes in the vascular smooth muscle, e.g. Ca2+-entry blockers or angiotensin converting enzyme (ACE) inhibitors. However, the extent of these influences depends on which agonist is used. The pressor response to intravenous injection of alpha-adrenoceptor agonists consists of two phases: an initial rapid but transient response (phase I) is followed by a response of slower onset but longer duration (phase II). We have examined the effects of manipulation of arterial blood gases, a Ca2+-entry blocker, nifedipine, and an ACE inhibitor, teprotide, on the pressor responses to a series of alpha-adrenoceptor agonists. In each case, the effects showed selectivity for one or other of the two phases and the differences in susceptibility between agonists could be explained by the relative sizes of the two phases in their responses. In general, phase II was more susceptible to alkalosis, nifedipine and teprotide, so that drugs in which this component predominated were more susceptible to these factors. In contrast there was no direct correlation with the receptor subtypes activated by the agonists.