A drug-drug interaction study and physiologically based pharmacokinetic modelling to assess the effect of an oral 5-lipoxygenase activating protein inhibitor on the pharmacokinetics of oral midazolam.

AIMS: Early clinical studies have indicated that the pharmacokinetics of Atuliflapon (AZD5718) are time and dose dependent. The reason(s) for these findings is(are) not fully understood, but pre-clinical profiling suggests that time-dependent CYP3A4 inhibition cannot be excluded. In clinical practice, Atuliflapon will be co-administered with CYP3A4 substrates; thus, it is important to determine the impact of Atuliflapon on the pharmacokinetics (PK) of CYP3A4 substrates. The aim of this study was to evaluate the effect of Atuliflapon on the pharmacokinetics of a sensitive CYP3A4 substrate, midazolam, and to explore if the time-/dose-dependent effect seen after repeated dosing could be an effect of change in CYP3A4 activity. METHODS: Open-label, fixed-sequence study in healthy volunteers to assess the PK of midazolam alone and in combination with Atuliflapon. Fourteen healthy male subjects received single oral dose of midazolam 2 mg on days 1 and 7 and single oral doses of Atuliflapon (125 mg) from days 2 to 7. A physiologically based pharmacokinetic (PBPK) model was developed to assess this drug-drug interaction. RESULTS: Mean midazolam values of maximum plasma concentration (Cmax) and area under the curve (AUC) to infinity were increased by 39% and 56%, respectively, when co-administered with Atuliflapon vs. midazolam alone. The PBPK model predicted a 27% and 44% increase in AUC and a 23% and 35% increase in Cmax of midazolam following its co-administrations with two predicted therapeutically relevant doses of Atuliflapon. CONCLUSIONS: Atuliflapon is a weak inhibitor of CYP3A4; this was confirmed by the validated PBPK model. This weak inhibition is predicted to have a minor PK effect on CYP3A4 metabolized drugs.

Comprehensive clinical pharmacology characterization of AZD4635 in healthy participants to support dosing considerations.

AIMS: Two phase 1 studies characterized the oral bioavailability of AZD4635 (potential anticancer therapy) and factors that may influence its pharmacokinetics (PKs; food, smoking, proton-pump inhibitors [PPIs] and CYP1A2 inhibitors) to support continued clinical development of AZD4635. METHODS: Study 1 (comparative PK study; nonsmokers) consists of Part A and Part B. Participants (fasted) in Part A were administered 50 mg of AZD4635 either as nanosuspension or capsule. In Part B, these participants were administered a 50-mg capsule either following a high-fat meal or with a PPI in the fasted state. In Study 2 (CYP1A2 mediated drug-drug interaction study), a 25-mg AZD4635 capsule was administered to smokers and nonsmokers (fasted) with or without 100 mg of fluvoxamine. RESULTS: In Study 1 (N = 21), AZD4635 exposure was comparable between the capsule and nanosuspension. The high-fat meal produced a 12% decrease in AUCinf , a ≥50% reduction in Cmax and delayed absorption (Tmax : 4.0 h vs 1.5 h) for the capsule. The PPI did not affect the oral bioavailability of the AZD4635 capsule. In Study 2 (N = 28), AZD4635 + fluvoxamine (compared with AZD4635 alone) produced ~5-fold increases in AUCinf , 2-fold increases in Cmax and prolonged AZD4635 elimination half-life in smokers (22.7 vs 9.0 h) and nonsmokers (22.4 vs 9.2 h). All treatment regimens were well tolerated. The most common adverse events included dizziness, nausea and headache. CONCLUSIONS: The high-fat meal reduced the rate but not the extent of AZD4635 absorption. The effect of gastric pH on AZD4635 was minimal. Smoking had no effect on the exposure (Cmax and AUCinf ) of AZD4635, while fluvoxamine increased AZD4635 Cmax and total exposure. No new safety concerns were identified.

Effect of Various Dosing Schedules on the Pharmacokinetics of Oral Semaglutide: A Randomised Trial in Healthy Subjects.

BACKGROUND: Prescribing information instructs taking oral semaglutide (a glucagon-like peptide-1 analogue) in the fasting state, followed by a post-dose fasting period of ≥ 30 min. This trial compared the recommended dosing schedule with alternative schedules. METHODS: This was a randomised, single-centre, multiple-dose, open-label, five-armed, parallel-group trial in healthy subjects who received once-daily oral semaglutide (3 mg for 5 days followed by 7 mg for 5 days). Subjects (n = 156) were randomised to five dosing schedules: 2-, 4-, or 6-h pre-dose fast followed by a 30-min post-dose fast (treatment arms: 2 h-30 min, 4-30 min, 6 h-30 min); 2-h pre-dose fast followed by an overnight post-dose fast (treatment arm: 2 h-night); or overnight pre-dose fast followed by a 30-min post-dose fast (reference arm: night-30 min). Semaglutide plasma concentration was measured regularly until 24 h after the 10th dose. Endpoints included area under the semaglutide plasma concentration-time curve during a 24-h interval after the 10th dose (AUC0-24h) (primary endpoint) and maximum observed semaglutide plasma concentration after the 10th dose (Cmax) (secondary endpoint). RESULTS: Compared with an overnight pre-dose fast (reference arm: night-30 min), shorter pre-dose fasting times in the 2 h-night, 2 h-30 min, 4 h-30 min, and 6 h-30 min treatment arms resulted in significantly lower semaglutide AUC0-24h and Cmax after the 10th dose (estimated treatment ratio ranges: 0.12-0.43 and 0.11-0.44, respectively; p < 0.0001 for all comparisons). Semaglutide AUC0-24h and Cmax after the 10th dose were similar for the 2 h-30 min and 2 h-night treatment arms. CONCLUSION: This trial supports dosing oral semaglutide in accordance with prescribing information, which requires dosing in the fasting state. TRIAL REGISTRATION: ClinicalTrials.gov (NCT04513704); registered August 14, 2020.

Oral semaglutide is a human glucagon-like peptide-1 analogue that has been approved for the treatment of type 2 diabetes. It has been established that taking oral semaglutide with food or large volumes of water decreases absorption of the drug in the body. Current prescribing information instructs taking oral semaglutide on an empty stomach (known as the fasting state), with 120 mL/4 oz of water, then waiting for at least 30 min before consuming any food, water, or taking other oral medications. This study investigates whether different dosing schedules for oral semaglutide could potentially offer more flexibility to patients in the timing of their oral semaglutide dosing. The trial, conducted in healthy volunteers, compares the dosing schedule described in the prescribing information with different fasting times before (pre-dose) and after (post-dose) taking oral semaglutide during the day or evening, to see if there were any effects on the concentration of drug in the body. Compared to the recommended overnight fasting period, shorter pre-dose fasting periods of 2­6 h with a 30-min post-dose fast considerably reduced semaglutide exposure in the body. Similarly, semaglutide exposure was also reduced with a 2-h pre-dose fast combined with post-dose overnight fasting. These findings further support the current prescribing information, which states that patients should take their oral semaglutide dose after an overnight fast.

Pharmacokinetic, Safety, and Pharmacodynamic Properties of Teverelix Trifluoroacetate, a Novel Gonadotropin-Releasing Hormone Antagonist, in Healthy Adult Subjects.

Teverelix trifluoroacetate is a decapeptide, gonadotropin-releasing hormone antagonist that binds competitively and reversibly to gonadotropin-releasing hormone receptors in the pituitary gland, resulting in immediate suppression of luteinizing hormone and follicle-stimulating hormone, which in turn causes a very rapid decrease in testosterone production in the Leydig cells of the testes in men and in estradiol in the ovaries in women. This phase 1 clinical study was an open-label, parallel-design, single-center, single-dose study in older, healthy male subjects. Following injection, teverelix is released into the systemic circulation in a biphasic manner. An initial rapid phase is followed by a slow-release phase thought to be due to the formation of a depot, which limits the diffusion of teverelix into the blood. The release characteristics differ significantly for the subcutaneous (SC) and intramuscular (IM) routes. Teverelix maximum concentration and exposure increased in an approximately dose-proportional manner across the 60 to 120 mg SC doses. All 3 pharmacodynamic end points (luteinizing hormone, follicle-stimulating hormone, and total testosterone) showed reductions that were more prolonged following the 90 mg IM administration compared to 90 mg SC administration.

Comparison of autoinjector with accessorized prefilled syringe for benralizumab pharmacokinetic exposure: AMES trial results.

OBJECTIVE: We compared the pharmacokinetic exposure following a single subcutaneous dose of benralizumab 30 mg using either autoinjectors (AI) or accessorized prefilled syringes (APFS). APFS and AI functionality and reliability for at-home benralizumab delivery have been demonstrated in the GREGALE and GRECO studies, respectively. METHODS: In the open-label AMES study (NCT02968914), 180 healthy adult men and women were randomized to one of two device (AI or APFS) and three injection site (upper arm, abdomen, or thigh) combinations. Randomization was stratified by weight (<70 kg, 70-84.9 kg, and ≥85 kg). Blood eosinophil counts were measured on Days 1, 8, 29, and 57. RESULTS: Benralizumab pharmacokinetic exposure was similar between AI and APFS. Geometric mean ratios (AI/APFS) (90% CI) were 92.8% (87.4-98.6) and 94.5% (88.2-101.2) for two area under the concentration‒time curve measurements (AUClast and AUCinf). Benralizumab exposure was approximately 15-30% greater for thigh vs. abdomen or upper arm administration. Exposure was slightly greater for APFS vs. AI regardless of injection site or weight class. These differences were unlikely to be clinically relevant, as eosinophil depletion was achieved consistently with both devices at all injection sites. No device malfunctions were reported. No new or unexpected safety findings were observed. CONCLUSION: Benralizumab pharmacokinetic exposure was similar between AI and APFS, with consistent blood eosinophil count depletion observed with both devices. These results support benralizumab administration with either AI or APFS, providing patients and physicians increased choice, flexibility, and convenience for potential at-home delivery.

Mass flux decay timescales of volcanic particles due to aeolian processes in the Argentinian Patagonia steppe.

We investigate the timescales of the horizontal mass flux decay of wind remobilised volcanic particles in Argentina, associated with the tephra-fallout deposit produced by the 2011-2012 Cordón Caulle (Chile) eruption. Particle removal processes are controlled by complex interactions of meteorological conditions, surface properties and particle depletion with time. We find that ash remobilisation follows a two-phase exponential decay with specific timescales for the initial input of fresh ash (1-74 days) and the following soil stabilisation processes (3-52 months). The characteristic timescales as a function of particle size shows two minimum values, identified for sizes around 2 and 19-37 [Formula: see text]m, suggesting that these size-range particles are remobilised more easily, due to the interaction between saltation and suspension-induced processes. We find that in volcanic regions, characterised by a sudden release and a subsequent depletion of particles, the availability of wind-erodible particles plays a major role due to compaction and removal of fine particles. We propose, therefore, a simple and reproducible empirical model to describe the mass flux decay of remobilised ash in a supply-limited environment. This methodology represents an innovative approach to link field measurements of multi-sized and supply-limited deposits with saltation erosion theory.

Safety, Tolerability, and Pharmacokinetics of the Mineralocorticoid Receptor Modulator AZD9977 in Healthy Men: A Phase I Multiple Ascending Dose Study.

Excessive activation of the mineralocorticoid receptor (MR) underlies the pathophysiology of heart failure and chronic kidney disease. Hyperkalemia risk limits the therapeutic use of conventional MR antagonists. AZD9977 is a nonsteroidal, selective MR modulator that may protect nonepithelial tissues without disturbing electrolyte balance. This phase I study investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple oral doses of AZD9977 in healthy volunteers. Twenty-seven male participants aged 23-45 years were randomized 3:1 to receive oral AZD9977 or placebo for 8 days (with twice-daily dosing on days 2-7), in dose cohorts of 50, 150, and 300 mg (AZD9977, n = 6 per cohort; placebo, n = 3 per cohort). Adverse events occurred in 4 of 18 participants receiving AZD9977 (22.2%) and 6 of 9 receiving placebo (66.7%), all of mild or moderate severity; none were serious or led to withdrawal. AZD9977 was rapidly absorbed, with median time of maximum concentration of 0.50-0.84 hours across dose groups. Area under the curve and maximum concentration were approximately dose proportional but elimination and accumulation terminal half-life increased with dose. Steady-state was reached after 3-4 days, with dose-dependent accumulation of 1.2-1.7-fold. Renal clearance was 5.9-6.5 L/hour and 24-37% of AZD9977 was excreted in the urine. Serum aldosterone levels increased dose dependently from days -1 to 7 in participants receiving AZD9977, but serum potassium levels and urinary electrolyte excretion were unchanged. AZD9977 was generally well-tolerated with no safety concerns. Exploratory outcomes suggested reduced hyperkalemia risk compared with MR antagonists. These findings support further clinical development of AZD9977.

Phase 1 Pharmacokinetic Study of AZD5718 in Healthy Volunteers: Effects of Coadministration With Rosuvastatin, Formulation and Food on Oral Bioavailability.

AZD5718 is a first-in-class small-molecule anti-inflammatory drug with the potential to reduce the residual risk of cardiovascular events after myocardial infarction in patients receiving lipid-lowering statin therapy. Leukotrienes are potent proinflammatory and vasoactive mediators synthesized in leukocytes via 5-lipoxygenase and 5-lipoxygenase-activating protein (FLAP). AZD5718 is a FLAP inhibitor that dose-dependently reduced leukotriene biosynthesis in a first-in-human study. We enrolled 12 healthy men in a randomized, open-label, crossover, single-dose phase 1 pharmacokinetic study of AZD5718 to investigate a potential drug-drug interaction with rosuvastatin, and the effects of formulation and food intake (ClinicalTrials.gov identifier: NCT02963116). Rosuvastatin (10 mg) were absorbed more rapidly when coadministered with AZD5718 (200 mg), probably owing to weak inhibition of hepatic statin uptake, but relative bioavailability was unaffected (geometric least-squares mean ratio [GMR], 100%; 90% confidence interval [CI], 86%-116%). AZD5718 pharmacokinetics were unaffected by coadministration of rosuvastatin. AZD5718 (200 mg) was absorbed less rapidly when formulated as tablets than oral suspension, with reduced relative bioavailability (GMR, 72%; 90%CI, 64%-80%). AZD5718 absorption was slower when 200-mg tablets were taken after a high-fat breakfast than after fasting, but relative bioavailability was unaffected (GMR, 96%; 90%CI, 87%-106%). In post hoc pharmacodynamic simulations, plasma leukotriene B4 levels were inhibited by >90% throughout the day following once-daily AZD5718, regardless of formulation or administration with food. AZD5718 was well tolerated, with no severe or serious adverse events. These data supported the design of a phase 2a efficacy study of AZD5718 in patients with coronary artery disease.

Effect of a spacer on total systemic and lung bioavailability in healthy volunteers and in vitro performance of the Symbicort® (budesonide/formoterol) pressurized metered dose inhaler.

INTRODUCTION: Many patients with chronic obstructive pulmonary disease or asthma experience difficulties in coordinating inhalation with pressurized metered-dose inhaler (pMDI) actuation. The use of a spacer device can improve drug delivery in these patients. The aim of this study was to establish the relative bioavailability of single doses of Symbicort® (budesonide/formoterol) pMDI 160/4.5 µg/actuation (2 actuations) used with and without a spacer device. In addition, an in vitro study was conducted to characterize performance of the inhaler when used in conjunction with a spacer device. METHODS: A Phase I, randomized, open-label, single-dose, single-center, crossover study in 50 healthy volunteers (NCT02934607) assessed the relative bioavailability of single-dose Symbicort® pMDI 160/4.5 µg/actuation (2 actuations) with and without a spacer (AeroChamber Plus® Flow-Vu®). Inhaled doses were administered without or with activated charcoal (taken orally) to estimate total systemic exposure and exposure through the lung, respectively. The in vitro study characterized the effect of the spacer with respect to delivered dose, fine particle dose, and dose during simulated breathing of budesonide and formoterol. RESULTS: In terms of total systemic exposure, use of the spacer increased the relative bioavailability determined by AUC(0-last) and Cmax by 68% (spacer:no spacer treatment ratio, 167.9%; 90% CI, 144.1 to 195.6) and 99% (ratio, 198.7%; 90% CI, 164.4 to 240.2) for budesonide, and 77% (ratio, 176.6%; 90% CI, 145.1 to 215.0) and 124% (ratio, 223.6%; 90% CI, 189.9 to 263.3) for formoterol, respectively, compared with pMDI alone. Similarly, the lung exposure of budesonide and formoterol increased (AUC(0-last) and Cmax by 146% [ratio, 246.0%; 90% CI, 200.7 to 301.6] and 127% [ratio, 226.5%; 90% CI, 186.4 to 275.4] for budesonide, and 173% [ratio, 272.8%; 90% CI, 202.5 to 367.4] and 136% [ratio, 236.2%; 90% CI, 192.6 to 289.6] for formoterol, respectively) when the pMDI was administered through the spacer. When assessed by AUC(0-last) quartile without spacer, subjects in the lowest exposure quartile (indicating poor inhalation technique) with Symbicort® pMDI 160/4.5 µg/actuation (2 actuations) had markedly increased total systemic and lung exposure when the same dose was administered with the spacer. In contrast, for subjects in the highest exposure quartile with pMDI alone, total systemic and lung exposure of formoterol and budesonide was similar with and without the spacer. In the in vitro study, the fine particle dose (<5 µm) of both budesonide and formoterol from the spacer at delay time (i.e. pause period after actuation) = 0 s (instantaneous) after actuation was similar to the fine particle dose when not using the spacer. The delivered doses of budesonide and formoterol from the spacer were both lower compared with the doses administered without the spacer. There was also a decrease in delivered dose with increasing delay time. CONCLUSIONS: The clinical study demonstrated that in subjects with poor inhalation technique the use of the AeroChamber Plus® Flow-Vu® spacer increased the bioavailability of Symbicort® pMDI to a level observed in subjects with good inhalation technique without a spacer. The findings from the in vitro study support the fine particle dose characteristics of Symbicort® pMDI with the AeroChamber Plus® Flow-Vu® spacer.

Dipeptidyl Peptidase 1 Inhibitor AZD7986 Induces a Sustained, Exposure-Dependent Reduction in Neutrophil Elastase Activity in Healthy Subjects.

Neutrophil serine proteases (NSPs), such as neutrophil elastase (NE), are activated by dipeptidyl peptidase 1 (DPP1) during neutrophil maturation. High NSP levels can be detrimental, particularly in lung tissue, and inhibition of NSPs is therefore an interesting therapeutic opportunity in multiple lung diseases, including chronic obstructive pulmonary disease (COPD) and bronchiectasis. We conducted a randomized, placebo-controlled, first-in-human study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple oral doses of the DPP1 inhibitor AZD7986 in healthy subjects. Pharmacokinetic and pharmacodynamic data were analyzed using nonlinear mixed effects modeling and showed that AZD7986 inhibits whole blood NE activity in an exposure-dependent, indirect manner-consistent with in vitro and preclinical predictions. Several dose-dependent, possibly DPP1-related, nonserious skin findings were observed, but these were not considered to prevent further clinical development. Overall, the study results provided confidence to progress AZD7986 to phase II and supported selection of a clinically relevant dose.

A noninvasive, sensitive, specific, and reliable approach to assess whole-body nitric oxide synthesis in children.

Determination of nitric oxide (NO) synthesis in vivo is essential to understand the pathophysiologic role and therapeutic implications of the L-arginine/NO pathway in pediatric diseases. The aim of this study was to establish a noninvasive, sensitive, specific, and reliable approach to determine whole-body NO synthesis in healthy children. Seventeen healthy children (eight boys/nine girls, 4-16 y) were studied twice, and six of them on three occasions. Fasting children received a single oral dose of nonradioactive L-[15N]2-guanidino arginine (5 mg/kg body weight). Complete 24-h urine collections were subsequently performed on an ambulatory basis. Total urinary nitrate excretion and [15N]nitrate enrichments were determined using high-pressure liquid chromatography and gas chromatography-isotope ratio mass spectrometric techniques. The mean urinary [15N]nitrate enrichments on the 0-12-h/12-24-h collection periods of three study visits were 0.9309%/0.5910%, 0.9056%/0.6214%, and 0.9087%/0.6059%. The levels of 24-h urinary [15N]nitrate excretion [mean (95% confidence interval)] for three study visits were 11.70 (8.85-14.54), 12.21 (9.61-14.82), and 11.37 (7.96-14.77) microg [15N]nitrogen-nitrate/mmol creatinine, respectively. Within-subject coefficient of variation for 24-h urinary [15N]nitrate excretion was 11.87%. Agreement among results was assessed by intraclass correlation coefficient (0.93) and coefficient of repeatability (4.08). The percentage of L-[15N]2-guanidino arginine dose directed to nitric oxide synthesis was 0.221% [0.181-0.261]. Multiple regression analysis showed age as the predictor variable of whole-body NO synthesis. These results show for the first time that a single oral administration of L-[15N]2-guanidino arginine can be used to reliably and specifically determine whole-body NO synthesis in children.

The effects and metabolic fate of nitroflurbiprofen in healthy volunteers.

OBJECTIVE: Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) are a new class of cyclooxygenase (COX) inhibitors. To investigate whether these drugs actually release nitric oxide (NO), we labeled the nitroxy group of nitroflurbiprofen with nitrogen 15 to determine the metabolic fate of this compound in humans. METHOD: Six healthy volunteers who fasted were given an oral dose of 15 N-nitroflurbiprofen (100 mg). Samples of blood, urine, and gastric headspace gas were taken over a 24-hour period to determine the levels of nitroflurbiprofen, flurbiprofen, total nitrate/nitrite, 15 N-nitrate/nitrite, COX activity, and gastric NO. In a crossover study (1 week apart), a further 6 healthy volunteers who fasted were given an oral dose of nitroflurbiprofen (100 mg) or flurbiprofen (65 mg) and levels of gastric NO were determined. RESULTS: Nitroflurbiprofen was undetectable in the systemic circulation. Levels of 15 N-nitrate/nitrite (5.2% +/- 1.5% enrichment) and flurbiprofen (2.4 +/- 0.7 microg/mL) peaked at 4 hours in the plasma and gradually decreased thereafter. In unstimulated blood, the plasma levels of thromboxane B 2 (COX-1 activity) were 2 to 3 ng/mL, and after calcium ionophore stimulation, large amounts of thromboxane B 2 were produced (112 +/- 31 ng/mL). Prostaglandin E 2 was undetectable in unstimulated blood. After lipopolysaccharide stimulation, the plasma levels of prostaglandin E 2 increased to 15 +/- 4 ng/mL. The metabolite flurbiprofen inhibited plasma COX-1 activity for the duration of the study period (maximum inhibition at 4 hours), whereas COX-2 activity recovered after 6 hours. In the crossover study, levels of gastric NO were higher in subjects given nitroflurbiprofen, when compared with those given flurbiprofen. (The area under the curve for gastric NO was 435 +/- 107 ppm . h versus 305 +/- 94 ppm . h [95% confidence interval of the difference, 89-172 ppm . h; P < .001]). CONCLUSION: Nitroflurbiprofen was undetectable in the systemic circulation, suggesting metabolism to 15 N-nitrate/nitrite and flurbiprofen in the presystemic circulation. Levels of gastric NO were significantly higher after ingestion of nitroflurbiprofen than flurbiprofen.

Effect of Domperidone on the Bromocriptine-Induced Antihypertensive Action in Hypertensive Patients.

Dopaminergic receptors have been involved in the cardiovascular and renin-angiotensin systems (RAS). We have recently reported that bromocriptine is an effective antihypertensive drug by stimulating DA(2) dopaminergic receptors. However, the nature of the dopaminergic receptors in RAS has not been established. Ten outpatients with essential hypertension were treated at the Vargas Hospital with bromocriptine (BR) (11.25 mg day(minus sign1)), a DA(2) dopaminergic agonist, for a 2-week period, after which an oral dose of 30 mg day(minus sign1) of domperidone (DO), a peripheric DA(2) dopaminergic antagonist, was added for 2 additional weeks. The active period was preceeded by a 2-week placebo period. Bromocriptine decreased blood pressure (BP) significantly by 19/9 mm Hg (systolic/diastolic BP). Bromocriptine did not cause heart rate (HR) changes. Bromocriptine decreased plasma aldosterone (ALD) without altering plasma renin activity (PRA). Domperidone partially blocked bromocriptine-induced antihypertensive submaximal treadmill effects and reversed ALD decrease. Exercise response was not significantly altered by BR + DO. We conclude the following: (1) BR is an effective antihypertensive agent; (2) BR seems to be acting at both the central and peripheric nervous systems, and (3) the nature of the dopaminergic receptor involved in renin secretion does not seem to be DA(2).

Dopaminergic Influence on the Cardiovascular and Hormonal Responses to Cold Stress in Hypertensive Patients.

Immersion of one hand into ice water (cold pressor test) in eight hypertensive subjects induces elevation of mean arterial pressure, increase in heart rate, and no significant changes of plasma renin activity and plasma aldosterone concentrations. Domperidone, a DA2 dopaminergic antagonist, attenuates heart rate increase induced by the cold pressor test, and the combination of bromocriptine, a known DA2 dopaminergic agonist, with domperidone again provoked a heart rate increase during the cold pressor test. Domperidone caused an increase of both plasma renin activity and plasma aldosterone concentrations, which were reversed by bromocriptine. These results suggest that a dopamine-receptor stimulation is taking place during the cold pressor test.

Respuestas cardiovasculares y hormonales durante la exposición al frío: un estudio comparativo en normotensos y pacientes hipertensos / Cardiovascular and hormonal responses during cold exposure: a comparative study in normotensive and hypertensive patients

Hemos examinado las respuestas cardiovasculares (presión arterial, frecuencia cardiaca (FC) y hormonales (actividad renina plasmática (ARP), concentración de aldosterona plasmática (CAP) en sujetos normotensos e hipertensos. Se estudiaron 21 voluntarios sanos y 25 pacientes con hipertensión arterial esencial (HAE) en el Hospital Vargas de Caracas. Todos fueron sometidos a la prueba presora al frío (PPF). Hubo en ambos grupos un incremento de presión arterial, la cual fue mayor en hipertensos que en normotensos. Según la reactividad al frío, los normotensos fueron clasificados en dos grupos: Hiperreactores e hiporreactores. En hiporreactores (n=9) hubo incremento significativo de la presión arterial (13,4mmHg) sin alteraciones significativas en la FC, ARP y CAP. En hiperreactores (n=12) hubo un incremento significativo mayor (26,6mmHg) pero similar al de los hipertensos (23,9mmHg). En los tres grupos hubo una disminución de la ARP pero ésta fue significativa sólo en hiperreactores. Nuestro estudio sugiere una probable interrelación entre los efectos cardiovasculares y las respuestas hormonales en normotensos e hipertensos