Oral contraceptives modulate the muscle metaboreflex in healthy young women.

There are known sex differences in blood pressure regulation. The differences are related to ovarian hormones that influence ß-adrenergic receptors and the transduction of muscle sympathetic nerve activity. Oral contraceptives (OC) modulate the ovarian hormonal profile in women and therefore may alter the cardiovascular response. We questioned if OC would alter the absolute pressor response to static exercise and influence the day-to-day variability of the response. Healthy men (n = 11) and women (n = 19) completed a familiarization day and 2 experimental testing days. Women were divided into those taking (W-OC, n = 10) and not taking (W-NC, n = 9) OC. Each experimental testing day involved isometric handgripping exercise, at 30% of maximal force, followed by circulatory occlusion to isolate the metaboreflex. Experimental days in men were 7-14 days apart. The first experimental testing in W-OC occurred 2-7 days after the start of the active phase of their OC. Women not taking OC were tested during the early and late follicular phase of the menstrual cycle as determined by commercial ovulation monitor. The increase in mean arterial pressure (MAP) during exercise was significantly lower in W-NC (95 ± 4 mm Hg) compared with men (114 ± 4 mm Hg) and W-OC (111 ± 3 mm Hg) (P < 0.05), with the differences preserved during circulatory occlusion. The rise in MAP was significantly correlated between the 2 testing days in men (r = 0.72, P < 0.01) and W-OC (r = 0.77, P < 0.05), but not in W-NC (r = 0.17, P = 0.67), indicating greater day-to-day variation in W-NC. In conclusion, OC modulate the exercise pressor response in women and minimize day-to-day variability in the exercise metaboreflex.

Altered ß-adrenergic response in mice lacking myotonic dystrophy protein kinase.

The protein kinase product of the gene mutated in myotonic dystrophy 1 (DMPK) is reported to play a role in cardiac pathophysiology. To gain insight into the molecular mechanisms modulated by DMPK, we characterize the impact of DMPK ablation in the context of cardiac ß-adrenergic function. Our data demonstrate that DMPK knockout mice present altered ß-agonist-induced responses and suggest that this is due, at least in part, to a reduced density of ß(1)-adrenergic receptors in cardiac plasma membranes.

Cardiac risk stratification in patients with congestive heart failure: a catecholamines-beta-adrenoceptor-cAMP pathway.

OBJECTIVE: To investigate the stratification risk of catecholamines-beta-adrenoceptor (beta-AR)-cAMP pathway for cardiogenic death events in patients with congestive heart failure (CHF). METHODS: A total of 83 identified CHF patients with a baseline and follow-up plasma levels of norepinephrine (NE) and epinephrine (E), lymphocytes beta-AR density (Bmax), and intralymphocyte cAMP content in peripheral blood were followed up. Major cardiogenic death events were registered. RESULTS: The period between the initial entry and the last follow-up measurement were 51 +/- 16 months, the total duration of clinical follow-up after the last measurement were 14 +/- 8 months. During follow-up, 39 patients died of cardiogenic (sudden death 17 patients, worsening heart failure 22 patients). Persistence of high NE, E, and cAMP from baseline to follow-up were confirmed as risk predicting factors of cardiovascular events. Persistence NE above 4.0 nmol/L, E above 3.5 nmol/L, and the intralymphocyte cAMP content above 3.5 pmd x mg(-1) x pro(-1) from baseline to follow-up were significant adverse prognostic predictors. The major cardiogenic death events rates per 100 patients-years were 1.33 and 4.82 in patients with NE below and above 4.0 nmol/L (HR: 2.91; 95% CI: 1.08-7.33; P = 0.015); were 1.42 and 4.36 in the patients with E levels below and above 3.5 nmol/L (HR: 2.64; 95% CI: 1.02-6.41; P = 0.019); were 1.81 and 4.67 in the patients with the intralymphocyte cAMP content below and above 3.5 pmd x mg(-1) x pro(-1) (HR: 2.79; 95% CI: 1.04-6.83; P = 0.017), but difference was not significant between the beta-AR density below and above median. CONCLUSIONS: Persistent increase in circulating catecholamines and intralymphocyte cAMP content may increase the long-term mortality in CHF patients.

Regulation of the catecholamine beta-adrenergic system in ventricular remodeling of hypertension.

Differences in structural remodeling are believed to be influenced by hormonal systems in hypertension. The objective of the present study was to investigate the change in the circulating catecholamine beta-adrenergic system in the left ventricle remodeling process in hypertensives. One hundred and thirty-four men (mean age, 53 years) had essential hypertension and underwent echocardiography before treatment. Normal morphology (n = 26) and concentric remodeling (n = 41) were defined by a relative wall thickness at diastole (RWT) of < 0.44 and > or = 0.44, respectively, and concentric hypertrophy (n = 28) and eccentric hypertrophy (n = 39) by a left ventricular mass index (LVMI) of < 150 g/m(2) and > or = 150 g/m(2), respectively. Forty healthy males were studied as normal controls. Plasma levels of norepinephrine (NE) and epinephrine (E) were measured by high performance liquid chromatography. The density of lymphocyte beta-adrenoceptors (beta-AR) and the content of intralymphocyte cyclic AMP (cAMP) in peripheral blood were measured using (3)H-dihydroalpneol as a ligand and protein binding assay, respectively. The plasma levels of NE and E in the 4 groups of patients with essential hypertension were significantly increased compared with the control group. The density of lymphocyte beta-AR and the content of intralymphocyte cAMP of peripheral blood in the normal morphology, concentric remodeling, and concentric hypertrophy groups were significantly higher than those in the control group, while the values in the eccentric hypertrophy group were significantly lower than those in the control group. Among the 4 groups, the plasma levels of NE and E had increased the most in the normal morphology group, followed in decreasing order by the concentric remodeling, concentric hypertrophy, and eccentric hypertrophy groups; the density of lymphocyte beta-AR and the content of intralymphocyte cAMP of peripheral blood in the normal morphology, concentric remodeling, and concentric hypertrophy groups increased while they decreased in the eccentric hypertrophy group in patients with essential hypertension. The catecholamine beta-adrenergic system appears to be related to left ventricular remodeling of hypertension. In this process, catecholamines increased continually. The density of beta-AR and the content of cAMP in peripheral lymphocytes increased at first and then decreased.

Effects of catecholamine-beta-adrenoceptor-cAMP system on severe patients with heart failure.

OBJECTIVE: To investigate the association between catecholamine-beta-adrenoceptor (beta-AR)-adenosine 3', 5'-monophosphate (cAMP) system and long-term prognosis in patients with chronic heart failure (CHF). METHODS: The study population comprised 73 patients with CHF (EF: 23% +/- 10%) with a mean follow-up of 3.8 +/- 1.9 years. Plasma levels of norepinephrine (NE) were measured using high performance lipid chromatography, beta-adrenergic receptor density (Bmax) and the content of cAMP in peripheral lymphocytes were calculated using 3H-dihydroalpneolo as ligand and competitive immunoassay, respectively. Deaths due to cardiovascular events within the follow-up period were registered. RESULTS: The total mortality was 64.7%, 57.4% of which was for cardiogenic (worsening heart failure: 32.4%; sudden death: 25.0%). In the cardiogenic death group, plasma levels of NE and epinephrine (E) (3.74 nmol/L +/- 0.09 nmol/L and 3.17 nmol/L +/- 1.0 nmol/L) and the contents of peripheral lymphocyte cAMP (3.64 pmol/mg protein +/- 1.4 pmol/mg protein) were significantly increased as compared with the survival group (2.68 nmol/L +/- 0.07 nmol/L, 2.41 nmol/L +/- 0.24 nmol/L and 2.73 pmol/mg protein +/- 0.9 pmol/mg protein, respectively, all P < 0.01). In the sudden death group, plasma levels of NE and E (5.01 nmol/L +/- 0.06 nmol/L and 4.13 nmol/L +/- 0.08 nmol/L) were significantly increased as compared with the worsening heart failure group (2.49 nmol/L +/- 0.07 nmol/L and 2.33 nmol/L +/- 0.8 nmol/L, all P < 0.001) and to the survival group (2.68 nmol/L +/- 0.07 nmol/L and 2.41 nmol/L +/- 0.14 nmol/L, all P < 0.01). The incidences of sudden death were 0%, 75%, and 100% (chi(2) = 16.018, P < 0.01) in patients with plasma NE < 2.5 nmol/L, NE 2.5 nmol/L - 4.5 nmol/L, and NE > 4.5 nmol/L, respectively. In the worsening heart failure group, the content of peripheral lymphocyte cAMP (4.46 pmol/mg protein +/- 0.18 pmol/mg protein) was significantly increased compared with the sudden death group (2.39 pmol/mg protein +/- 0.9 pmol/mg protein, P < 0.001) and to the survival group (2.73 pmol/mg protein +/- 1.1 pmol/mg protein, P < 0.001). The worsening heart failure death occurences were 5.0%, 72.2%, and 100% (chi(2) = 14.26, P < 0.01) in patients with a content of peripheral lymphocyte cAMP < 2.5 nmol/L, cAMP 2.5 nmol/L - 4.5 nmol/L, and cAMP > 4.5 nmol/L, respectively. Bmax in peripheral lymphocyte was not significantly different (P > 0.05) among the sudden death, worsening heart failure, and survival groups in CHF patients. CONCLUSIONS: Plasma levels of catecholamine increase significantly, and Bmax and the contents of cAMP in peripheral lymphocytes decrease significantly in patients with CHF. High plasma catecholamine levels may be associated with sudden death, and high intralymphocyte cAMP content may be associated with worsening heart failure in CHF patients.

High plasma buffering and the absence of a red blood cell beta-NHE response in brown bullhead (Ameiurus nebulosus).

The high non-bicarbonate buffer capacity of brown bullhead (Ameiurus nebulosus) plasma was postulated to function as an alternative mechanism for the protection of red blood cell (RBC) intracellular pH (pHi) in the absence or attenuation of a RBC adrenergic response. The requirement for protecting RBC pHi arises from the presence of a Root effect haemoglobin in bullhead. In support of this hypothesis, bullhead RBCs incubated in vitro with isoproterenol (10(-8)-10(-5) mol l(-1)) or forskolin (10(-4) mol l(-1)) exhibited significant cyclic AMP accumulation, but failed to exhibit cell swelling or significant Na(+) or Cl(-) accumulation; plasma pH (pHe) was also unaffected. Similarly, no significant effect on RBC water content, Na(+) or Cl(-) concentration, or pHe was detected in bullhead blood incubated with 8-bromo cyclic AMP (10(-4)-10(-2) mol l(-1)) in vitro. These results suggest that while bullhead RBCs possess a beta-adrenoreceptor linked to cyclic AMP formation, stimulation of this adrenergic receptor does not result in measurable activation of a Na(+)/H(+) exchanger.

[Expression of beta 2-adrenoceptor on peripheral lymphocyte and the level of plasma cAMP in patients with pregnancy induced hypertension].

OBJECTIVE: To evaluate the alteration of beta 2-adrenoceptor-cAMP system in patients with pregnancy-induced hypertension (PIH). METHODS: The Bmax of beta 2-adrenoceptor on the lymphocyte was examined by radioligand binding technique. The level of plasma cAMP was observed by radio competitive protein binding assay. RESULTS: The Bmax of beta 2-adrenoceptor (259 fmol/10(6) cell +/- 22 fmol/10(6) cell) on the lymphocytes was significantly higher in PIH group than in control group (247 fmol/10(6) cell +/- 23 fmol/10(6) cell). There was no significant difference between the PIH group and the controls. The content of plasma cAMP (2.94 nmol/40 microliters +/- 0.91 nmol/40 microliters) was significantly higher in PIH group than in control group (0.19 nmol/40 microliters +/- 0.05 nmol/40 microliters). CONCLUSION: The mechanism of PIH may be related with the activity of beta 2-adrenoceptor-cAMP system.

Effect of ethanol drinking, hangover, and exercise on adrenergic activity and heart rate variability in patients with a history of alcohol-induced atrial fibrillation.

To elucidate the mechanism of alcohol-induced atrial fibrillation (AF) we studied the heart rate variability and parameters of the adrenergic system during alcohol intake, hangover, and exercise in 6 men (mean age 43 years) prone to alcohol-induced AF, together with 6 age-matched controls. The ambulatory (15 hour) electrocardiogram was recorded and blood samples were taken for lymphocytic beta adrenoceptor, plasma catecholamine, and cyclic adenosine monophosphate (cAMP) measurements before and after alcohol intake (blood alcohol 1.5 per thousand), during hangover, and after a standardized bicycle exercise test. The beta-adrenoceptor density in lymphocytes was unchanged in the control group after alcohol intake or during hangover. Each of the AF patients had an increase in beta-adrenoceptor density after ethanol drinking (mean increase 29%, p <0.05). The hangover or exercise beta-receptor values did not differ from those in corresponding controls. Plasma adrenaline concentration tended to decrease and noradrenaline to increase after drinking and during hangover in both groups. Plasma cAMP levels were lower in patients after drinking than in controls (p <0.05). The exercise values of the adrenergic parameters were very similar in AF patients whether or not preceded by alcohol. Analysis of ambulatory electrocardiography showed a very low rate of ectopic beats in both AF patients and controls. Analysis of heart rate variability revealed a tendency toward an increase in sympathetic/parasympathetic component ratio (low-frequency/high-frequency ratio) in AF patients, but not in controls, after ethanol drinking. In conclusion, no signs of arrhythmogenic cardiac disease were detected in patients with AF to explain the tendency toward AF. Increases in beta-adrenoceptor density and low-frequency/high-frequency ratio during ethanol intoxication in patients with AF suggest an exaggerated sympathetic reaction.

Seasonal variations in cyclic AMP production by peripheral blood mononuclear cells in allergic asthmatics.

BACKGROUND: Dysfunction of the beta-adrenoceptor (betaAR)/adenylyl cyclase (AC) system can impair the response of different cell types, including lymphocytes. In asthma, impairment of this system as well as changes in cytokine production by lymphocytes have been described. Because the severity of asthma can change over the year, a circannual pattern of the betaAR/AC system activity may also exist. OBJECTIVES: We set out to examine the activity of this betaAR/AC signal transduction system in peripheral blood mononuclear cells (PBMCs) of allergic asthmatics to asses whether differences existed between seasons. We investigated whether changes were associated with asthma severity and circannual changes in serum cortisol levels. METHODS: During 19 months, 41 allergic asthmatics (mean age 28 years) with nocturnal airway obstruction were enrolled in the study. AC activity was measured by cyclic AMP production. Resting, stimulated and potentiated AC activities and their relationships with clinical parameters, seasonal influences and serum cortisol levels were assessed. RESULTS: The AC activity in resting, stimulated and potentiated cells varied during the year. AC activity was relatively low in the periods June-August and September-November, and higher in December-February and March-May. Receptor-mediated and potentiated responses expressed as percentage of the resting response were equivalent throughout the year. Serum cortisol levels were positively related to AC activity. No relationships were found between clinical parameters and AC activity or serum cortisol levels. CONCLUSIONS: These results indicate that AC activity in PBMCs of allergic asthmatics shows a seasonal variation. However, seasonal differences in AC activity seems to be unrelated with clinical parameters. Other factors such as serum cortisol levels may have a modulating influence on AC activity. Future studies of AC systems in blood cells of asthmatic patients need to take into account these seasonal influences.

Allosteric equilibrium model explains steady-state coupling of beta-adrenergic receptors to adenylate cyclase in turkey erythrocyte membranes.

We used a simple experimental approach to clarify some contradictory predictions of the collision coupling and equilibrium models (e.g. ternary complex, two-state ternary complex or quinternary complex), which describe G-protein-mediated beta-adrenergic receptor signalling in essentially different manners. Analysis of the steady-state coupling of beta-adrenoceptors to adenylate cyclase in turkey erythrocyte membranes showed that: (1) in the absence of an agonist, Gpp(NH)p (a hydrolysis-resistant analogue of GTP) can activate adenylate cyclase very slowly; (2) this activity reaches a steady state in approx. 5 h, the extent of activity depending on the concentration of the nucleotide; (3) isoprenaline-activated steady-state adenylate cyclase can be inactivated by propranolol (a competitive antagonist that relaxes the receptor activation), in the presence of Gpp(NH)p (which provides a virtual absence of GTPase) and millimolar concentrations of Mg2+ (the rate of this inactivation is relatively fast); (4) increasing the concentration of Gpp(NH)p can saturate the steady-state activity of adenylate cyclase. The saturated enzyme activity was lower than that induced by isoprenaline under the same conditions. This additional agonist-induced activation was reversible. In the light of these results, we conclude that agonist can also activate the guanine nucleotide-saturated system in the absence of GTPase by a mechanism other than guanine nucleotide exchange. We explain these phenomena in the framework of a quinternary complex model as an agonist-induced and receptor-mediated dissociation of guanine nucleotide-saturated residual heterotrimer, the equilibrium concentration of which is not necessarily zero. These results, which suggest a continuous interaction between receptor and G-protein, can hardly be accommodated by the collision coupling model that was originally suggested for the present experimental system and then applied to many other G-protein systems. Therefore we attempt to unify the equilibrium and collision coupling approaches to provide a consistent theoretical basis for the G-protein-mediated beta-adrenergic receptor signalling in turkey erythrocyte membranes.

Beta-adrenoceptor regulation in insulin-dependent diabetes mellitus.

The study was performed to determine whether the regulation of mononuclear leukocyte beta-adrenergic receptors and responses was changed in insulin-dependent diabetes mellitus (IDDM). The concentrations of noradrenaline, the beta-adrenoceptor densities, basal cAMP levels and maximal isoprenaline-induced cAMP responses were the same in the diabetic and healthy subjects. After isoprenaline-promoted receptor internalization and uncoupling, the receptor densities and the responsiveness did not differ. In the control group, a highly significant correlation existed between the number of beta-adrenoceptors and maximal isoprenaline responses, before (r = 0.99, p less than 0.01) and after (r = 0.96, p less than 0.01) receptor internalization and uncoupling. This correlation between receptor densities and responses was not present in the IDDM group, which also showed elevated levels of plasma adrenaline. This study demonstrates that IDDM subjects have an unaltered mechanism of agonist-promoted beta-adrenoceptor internalization, but indicates a partial dysfunction of the beta-adrenoceptor-coupling to adenylate cyclase.

Reduction of lymphocytic beta-adrenoceptor level in chronic alcoholics and rapid reversal after ethanol withdrawal.

Plasma catecholamine levels, lymphocytic beta-adrenoceptor densities and lymphocytic cAMP production were studied in 10 male subjects attending a withdrawal clinic after prolonged alcohol abuse. On admission the mean beta-adrenoceptor density was 29 +/- 9 fmol mg-1 protein (about 60% of the mean level of healthy control subjects, P less than 0.002). The following day a significant elevation of the beta-adrenoceptor level up to 46 +/- 19 fmol mg-1 protein (P less than 0.05) took place. This was accompanied by a parallel activation of the beta-adrenoceptor-mediated cAMP production of the lymphocytes. No major changes in beta-adrenoceptor levels or cAMP production took place during the next 7 days. Plasma catecholamine levels were elevated at arrival and decreased steadily during the withdrawal period. In conclusion, chronic alcoholism is associated with a reduction of lymphocytic beta-adrenoceptor density and functioning, which is followed by a rapid reversal during abrupt ethanol withdrawal. Thus an accelerated responsiveness to catecholamines may occur during the first ethanol-free day of chronic alcoholics.

Inhibitory effects of pertussis toxin on the cAMP generating system in human mononuclear leucocytes.

In a previous investigation of children infected with pertussis during the first week of paroxysmal stage, we found a 50-75% reduction of the isoprenaline (IPN)-induced cAMP response in peripheral MN leucocytes. In order to characterize these findings further, intact human MN leucocytes from healthy adults were treated with PT in vitro. Basal, as well as prostaglandin E1-stimulated cAMP levels were decreased by PT in a dose-dependent fashion over a range of 0.01 to 1000 ng ml-1 to about 65% of control levels. Stimulation of PT-pretreated cells (100 ng ml-1, 90 min, 37 degrees C) showed significantly reduced IPN and PGE1-induced cAMP accumulation, indicated by a depression and shift of the dose-response curves to the right. In contrast, cAMP generation was unchanged by forskolin, a diterpene that is believed to directly stimulate adenylyl cyclase. The anti-allergic drug ketotifen had no direct effects on basal, IPN or PGE1-induced cAMP responses; however the inhibitory actions of PT pretreatment on cAMP levels were diminished (basal and isoprenaline-stimulated) or reversed (PGE1-stimulated). To further locate the site of impaired cAMP responses, beta-adrenoceptor binding, as well as displacement characteristics of the receptor, were estimated by 125I-cyanopindolol binding to a plasma membrane fraction pretreated with or without PT. No differences in beta-adrenoceptor number or in the affinities of the binding sites could be detected. These data are in close agreement with the findings on MN leucocytes from pertussis-infected children and support the notion of PT-induced impaired signal transduction in the cAMP generating system in human MN leucocytes.

86Rb(K) influx and [3H]ouabain binding by human platelets: evidence for beta-adrenergic stimulation of Na-K ATPase activity.

Although active transport of potassium into human platelets has been demonstrated previously, there is hitherto no evidence that human platelets have an ouabain-inhibitable Na-K ATPase in their membrane. The present study demonstrates active rubidium (used as an index of potassium influx), 86Rb(K), influx into platelets, inhibitable by ouabain, and also demonstrates the presence of specific [3H]ouabain binding by the human platelet. This 86Rb(K) influx was stimulated by adrenaline, isoprenaline, and salbutamol, but noradrenaline caused a mild inhibition. Active 86Rb(K) influx by platelets was inhibited markedly by timolol, mildly by atenolol, but not by phentolamine. Therefore, active 86Rb(K) influx in human platelets is enhanced by stimulation of beta adrenoceptors of the beta 2 subtype. The platelet may therefore replace the leukocyte in future studies of Na-K ATPase activity. This would be a considerable advantage in view of the ease and rapidity of preparation of platelets.

Reduced beta 2-adrenoceptor sensitivity in normal pregnancy but not in pregnancy-induced hypertension.

beta 2-Adrenoceptors on lymphocytes from healthy nonpregnant and pregnant women and patients with pregnancy-induced hypertension (PIH) were studied in vitro by a radioligand binding technique (125I-hydroxybenzylpindolol) and related to in vivo responses to infused adrenaline. Healthy pregnant women had significantly fewer beta 2-adrenoceptor binding sites than nonpregnant controls (47.1 +/- 5.6 vs. 73.6 +/- 10.5 fmol X mg-1 protein), PIH patients displaying intermediate values. Adrenaline-induced increases in plasma cyclic AMP (a beta 2-mediated in vivo response) also tended to be reduced during normal pregnancy. The systemic vasodilatation evoked by intravenously infused adrenaline and the density of lymphocyte beta 2-adrenoceptor binding sites were positively related in the nonpregnant controls (r = 0.50), but inversely related in both the pregnant controls (r = -0.40) and the PIH patients (r = -0.70). These regression lines differed significantly. The present results indicate a reduction of beta 2-adrenoceptor function during normal pregnancy, which is less pronounced in PIH, as well as an altered relationship between beta 2-mediated vasodilator responses and densities of beta 2-adrenoceptors on lymphocytes during pregnancy.

Regulation of the beta-receptor-adenylate cyclase system in lymphocytes of allergic patients with asthma: possible role for protein kinase C in allergen-induced nonspecific refractoriness of adenylate cyclase.

Allergen challenge of allergic patients with asthma caused various changes in the beta-receptor-adenylate cyclase system of lymphocyte membranes from these patients. These changes included uncoupling and down regulation of beta-adrenergic receptors and nonspecific refractoriness of adenylate cyclase, as demonstrated by reduced responses to isoproterenol (beta 2), histamine (H2), 5'-guanylylimidodiphosphate, and sodium fluoride. Since these changes could be due to desensitization by enhanced plasma levels of catecholamines and/or histamine during the allergic response, we explored the effects of these agonists on the beta-receptor-adenylate cyclase system in vitro with normal lymphocytes. In addition, we assessed the effect of the tumor-promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), on this system, since phorbol esters have been demonstrated to modulate several receptor systems, presumably via activation of protein kinase C. That both the agonists and PMA may cause refractoriness of lymphocyte adenylate cyclase was demonstrated, but, however, by apparently different mechanisms. The agonists isoproterenol and histamine induced only a specific desensitization of the homologous responses, whereas PMA-induced refractoriness was nonspecific in nature. Radioligand-binding studies demonstrated that both uncoupling and down regulation contributed to the isoproterenol-induced beta-adrenergic hyporesponsiveness, whereas beta-adrenergic receptor uncoupling but not beta-adrenergic receptor down regulation was involved in PMA-induced desensitization. Histamine had no effect on the beta-adrenergic system at all. The data suggest that the agonist-induced changes in the adenylate cyclase system are specifically located at the receptors, whereas PMA-induced refractoriness can be explained by alterations distal to the receptors, presumably at the stimulatory guanine nucleotide regulatory protein. Thus, enhanced levels of catecholamines or histamine could be involved in the development of receptor-specific changes in the lymphocyte adenylate cyclase system of allergic patients with asthma. However, they are unlikely to cause the nonspecific changes distal to the receptors. The latter changes could be induced by physiologic activation of protein kinase C during the allergic response by a still unknown stimulus, possibly via the receptor-mediated turnover of phosphatidylinositol 4,5-diphosphate.

Acute desensitization of lymphocyte beta-adrenergic-stimulated adenylate cyclase in old age and Alzheimer's disease.

The effect of prior incubation with a single concentration of isoproterenol (10(-4) M) for 2 hours at 37 degrees C on isoproterenol-stimulated cyclic AMP accumulation in intact lymphocytes from young, old and subjects with Alzheimer's disease was studied. In lymphocytes from all three subjects groups prior incubation of cells with isoproterenol resulted in a significant reduction of cyclic AMP accumulation upon subsequent stimulation with isoproterenol.

beta 2- and alpha 2-adrenergic receptors and receptor coupling to adenylate cyclase in human mononuclear leukocytes and platelets in relation to physiological variations of sex steroids.

In view of evidence, largely in animals, indicating effects of sex steroids on adrenergic receptors, we measured mononuclear leukocyte (MNL) beta 2-adrenergic receptors and adenylate cyclase sensitivity to stimulation by isoproterenol as well as platelet alpha 2-adrenergic receptors and sensitivity of sodium fluoride-stimulated adenylate cyclase to inhibition by epinephrine in 3 groups of normal humans with physiologically disparate levels of testosterone, estradiol, and progesterone (10 normal men and 10 normal women, the latter sampled in both the follicular and luteal phases of their menstrual cycles). Differences in testosterone, estradiol, and progesterone were as expected; testosterone levels were 10-fold higher in men, and progesterone levels were 20-fold higher in luteal phase women. T4, cortisol , and norepinephrine levels did not differ. Basal plasma epinephrine concentrations were slightly but significantly higher in luteal phase women [34 +/- 5 (+/-SE) pg/ml] than in follicular phase women (16 +/- 3 pg/ml; P less than 0.01) or men (20 +/- 3 pg/ml; P less than 0.05). There were no significant differences among these 3 groups in the densities or affinities of MNL beta 2-adrenergic or platelet alpha 2-adrenergic receptors or in the corresponding MNL and platelet adenylate cyclase sensitivities. Thus, there is not a generalized effect of physiological variations of testosterone, estradiol, and progesterone on adrenergic receptors or adenylate cyclase. To the extent that the adrenergic receptors and adenylate cyclase activities of circulating cells reflect those of extravascular catecholamine target cells, these data provide no support for a role of physiological variations of testosterone, estradiol, or progesterone in the regulation of catecholamine action in humans.

Decreased mononuclear cell beta-adrenergic receptors in bronchial asthma: parallel studies of lymphocyte and granulocyte desensitization.

To assess the interaction of bronchial asthma and beta-agonist drugs, beta-adrenergic receptors were measured in human mixed leukocyte, mononuclear cell, and polymorphonuclear leukocyte cell membranes simultaneously. The densities and affinities of beta-adrenergic receptors were determined, by Scatchard analysis, with a potent beta-antagonist 125I-hydroxybenzylpindolol (125I-HYP) and compared among 12 nonatopic controls (group I), 13 mild asthmatics not taking drugs (group II), and eight asthmatics receiving long-term beta-agonist therapy (group III). Our findings were as follows. (1) Asthmatics not taking drugs (group II) have significantly lower mean mononuclear leukocyte beta-adrenergic receptor density (p less than 0.05) but no significant difference in mean polymorphonuclear leukocyte beta-adrenergic receptor density than the control group. (2) Asthmatics receiving long-term beta-agonist treatment (group III) had significantly lower mean beta-adrenergic receptor density in all three cell fractions (p less than 0.05). (3) Group I and II females had a higher mean beta-adrenergic receptor density in mixed leukocyte and polymorphonuclear cell fractions than males (p less than 0.05). (4) Terbutaline sulfate clearly caused desensitization of beta-adrenergic receptors in human leukocyte membranes in vivo. These results show that beta-adrenergic receptor density is influenced by cell type, beta-adrenergic agonist administration, and sex; they also show that bronchial asthma itself is associated with lower lymphocyte beta-receptor density.