Beta-adrenergic Agonist Terbutaline Research Articles

SAT-078 Adrenergic Receptor Regulation of Intracellular Calcium in Human Adrenocortical Carcinoma HAC15 Cells

Intracellular calcium fluctuations may play a role in the control of corticosteroid synthesis and secretion by the adrenal cortex. Using live-cell imaging with the calcium-sensitive fluorescent probe Fluo-4 in a human adrenocortical carcinoma cell line (HAC15), we previously demonstrated that activation of M3 muscarinic receptors stimulates intracellular calcium oscillations, enhances aldosterone production, and increases expression of CYP11B2 (1). To further understand autonomic control of cortical cell function, we are investigating the role of adrenergic signalers in regulating calcium homeostasis in HAC15 cells. Activation of adrenergic receptors with the endogenous, non-selective agonists norepinephrine and epinephrine (10μM) causes single, large calcium transients that do not oscillate. A similar calcium response results from the alpha adrenergic agonist phenylephrine, while the beta adrenergic agonist terbutaline does not elicit calcium changes. Consistent with this, norepinephrine-induced calcium changes are blocked by the alpha adrenergic antagonist phentolamine, but not by the beta adrenergic antagonist propranolol. Taken together, these preliminary results suggest that alpha adrenergic receptors are the dominant adrenergic subtype in the human adrenal cortex. Further experiments will use radiolabel binding assays, subtype-selective alpha receptor modulators, and RT-PCR methods, to determine which alpha subtypes are present. Also, ELISA measurements of steroid production will determine the physiological consequence of adrenergic receptor activation.

Blocking of beta-2 adrenergic receptors hastens recovery from hypoglycemia-associated social withdrawal

Hypoglycemia is associated with a variety of adverse behaviors including fatigue, confusion and social withdrawal. While these clinical symptoms are well characterized, the mechanism of their cause is not understood. Here we investigated how insulin-induced hypoglycemia causes social withdrawal. Male 8-12-week-old C57BL/6J mice were injected intraperitoneally (IP) with or without and/or insulin, norepinephrine (NE) and epinephrine (Epi), terbutaline and butoxamine with subsequent measurement of blood glucose, social withdrawal and plasma catecholamines. Insulin generated (0.75h post-injection) significant hypoglycemia with blood glucose nadirs of 64+/-4 and 48+/-5mg/dl for 0.8 and 1.2units/kg of insulin, respectively. Insulin (0.8 or 1.2units/kg) caused near total social withdrawal at 0.75h with full recovery not occurring until 4h (0.8units/kg) or 8h (1.2units/kg) post-insulin injection. Insulin also caused a marked elevation in plasma catecholamines. Basal 12h fasting NE and Epi were 287+/-38 and 350+/-47pg/ml, respectively. Insulin at 0.8units/kg increased plasma NE and Epi to 994+/-73 and 1842+/-473pg/ml, respectively. Administration of exogenous NE or Epi caused social withdrawal similar in magnitude to insulin. Importantly, administration of the beta-2 adrenergic receptor agonist terbutaline also caused social withdrawal while administration of the beta-2 adrenergic receptor antagonist butoxamine blocked NE-induced social withdrawal. Finally, butoxamine blocked insulin-induced social withdrawal. These data demonstrate that hypoglycemia-associated social withdrawal is dependent on catecholamines via a beta-2 receptor-mediated pathway.

The Effect of Maternal Catecholamines on the Caliber of Gravid Uterine Microvessels

Changes in maternal catecholamines that accompany the onset of labor analgesia include a decrease in epinephrine (EPI) but no change in norepinephrine (NE). Because EPI exerts predominantly beta-adrenergic, and NE predominantly alpha-adrenergic effects in circulating concentrations, we hypothesized that these changes could lead to uterine arteriole vasoconstriction. Uterine microvessels (73-120 microm internal diameter, n = 18) were harvested from near-term pregnant Sprague-Dawley rats, isolated and studied in a pressurized no-flow state with video microscopy. Drugs were applied extraluminally to the superfusion reservoir and the steady-state vessel diameter recorded. Dose-response curves were constructed for NE with and without the addition of the alpha-adrenergic antagonist prazosin, EPI (after 20%-30% preconstruction with the thromboxane analog U46619) with and without the addition of the beta-adrenergic antagonist propranolol, and NE in the presence of 10(-8) M EPI. Washout experiments modeled the changes in circulating maternal catecholamines observed during onset of analgesia: 10(-8) M EPI and 10(-6.5) M of NE (the EC50) were added simultaneously, then washed with NE only, and then with the beta2-adrenergic agonist terbutaline and NE. The washout protocol was repeated in the presence of propranolol. NE caused dose-dependent vasoconstriction (P < 0.0001), which was blocked by prazosin (P < 0.0001). EPI, added to U46619-preconstricted microvessels, caused vasodilation at lower concentrations and vasoconstriction at higher doses (P < 0.0001). Propranolol converted this response to monophasic dose-dependent vasoconstriction (P < 0.0001). Pretreatment of nonprecontracted vessels with EPI, 10(-8) M, significantly attenuated NE-induced vasoconstriction (P < 0.0001). In washout experiments, removal of EPI with continued presence of NE resulted in vasoconstriction that was reversed by terbutaline. Propranolol blocked the effect of both EPI and terbutaline. The results demonstrate that EPI, in concentrations found in the plasma of laboring women, vasodilates uterine resistance vessels and attenuates NE-induced vasoconstriction. This observation may have implications for changes in uterine blood flow that may accompany the onset of labor analgesia in human parturients, as effective analgesia is accompanied by an acute decrease in circulating EPI levels.

Terbutaline inhibits corticotropin-releasing hormone (CRH) expression in human trophoblast cells

Objective. To evaluate the effect of beta-adrenergic agonists on the regulation of the expression of the placental corticotropin-releasing hormone (CRH) gene.Study design. Term placentae were collected at the time of elective cesarean section, and trophoblast cells were harvested, isolated, and cultured. The isolated trophoblasts were plated, cultured and subsequently treated with cortisol, terbutaline, RU486, or vehicle control. CRH expression, mRNA abundance of CRH, and the housekeeping gene beta-actin were evaluated by Northern blot analysis.Results. Exposure of the trophoblasts to terbutaline (10−8 M) inhibited the expression of the CRH gene as depicted by Northern blot analysis. Co-addition of terbutaline (10−8 M) and RU486 (10−6 M) did not block the stimulatory effects of RU486 on placental trophoblast cells.Conclusion. The beta-adrenergic agonist terbutaline inhibits the expression of CRH in human trophoblasts. This finding may provide insight into the mechanism of action of terbutaline as a tocolytic agent.

Beta adrenergic inhibition of capsaicin-induced, NK 1 receptor-mediated nerve growth factor biosynthesis in rat skin

Excitation of primary afferent neurons stimulates the expression of cytokines and nerve growth factor (NGF) in innervated tissues. Since NGF is a neurotrophic and immunomodulatory factor contributing to inflammatory hyperalgesia and tissue response to injury, this study was conducted in order to investigate the mechanisms by which afferent neuron stimulation by topical application of capsaicin increases NGF in the rat skin. Thereby it was sought to identify possible targets for pharmacological modulation of NGF biosynthesis. Topical capsaicin (>1 mg/ml ethanol) caused a concentration- and time-dependent increase in the concentration of NGF in rat skin. The capsaicin-induced increase of NGF was not significantly affected by indomethacin administered at a dose (2 mg/kg) that abolishes prostaglandin E 2 biosynthesis. The NGF increase was suppressed by treatment of rats with the selective tachykinin NK 1 receptor antagonist SR140333 (0.1 mg/kg), and by the beta adrenergic agonist terbutaline (0.3 mg/kg). The effect of terbutaline was reversed by the beta adrenergic antagonist propranolol (1 mg/kg). Terbutaline also inhibited the increase in NGF caused by intraplantar injection of the NK 1 receptor agonist substance P (SP), but did not significantly affect that caused by carrageenan. The results show that topical administration of capsaicin causes a primarily NK 1 receptor-dependent increase in the NGF content of rat skin, which is susceptible to inhibition by beta adrenergic agonists. These observations not only suggest regulation of skin NGF biosynthesis by afferent neuronal and adrenergic mechanisms, but also indicate possible targets for pharmacological modulation of skin NGF biosynthesis.

Effects of terbutaline on NGF formation in allergic inflammation of the rat.

1. The aim of this study was to determine the effects of the beta adrenergic agonist terbutaline on NGF increase caused by allergic inflammation in rats. 2. Intraplantar antigen injection in sensitized rats increased paw volume and stimulated NGF biosynthesis in the skin of the injected paw as determined 3 and 6 h after injection. Treatment of rats with terbutaline (0.1 - 0.3 mg kg(-1), s.c.) had no significant effect on the NGF concentration in non-inflamed skin, but reduced oedema, and at 0.3 mg kg(-1) also NGF mRNA and immunoreactive NGF in the skin of the inflamed paw in a propranolol-reversible manner. In carrageenan-induced inflammation, terbutaline did not significantly reduce the inflammation-induced increase of NGF in paw skin. 3. Exposure of sensitized rats to aerosolized antigen (twice, 24 h interval) increased protein content, eosinophil leukocytes, and immunoreactive NGF in the bronchoalveolar lavage fluid (BAL, obtained 16 h after the second antigen exposure). Treatment of rats with terbutaline (0.3 mg kg(-1), s.c. 30 min before the second antigen challenge) suppressed antigen-induced elevation of protein and eosinophil leukocytes, and reduced the concentration of NGF in BAL to values similar to those found in non-sensitized rats. 4. The present results demonstrate anti-allergic properties of terbutaline in rats that were accompanied by a marked reduction of antigen-induced NGF increase in skin and BAL, respectively. These results are compatible with the assumption that terbutaline primarily suppressed the immune response to antigen thereby attenuating the release of vasoactive mediators and the stimulation of NGF biosynthesis.

Disturbed neuroendocrine-immune interactions in chronic fatigue syndrome.

The present study was designed to investigate the interaction between neuroendocrine mediators and the immune system in chronic fatigue syndrome (CFS). We examined the sensitivity of the immune system to the glucocorticoid agonist dexamethasone and the beta2-adrenergic agonist terbutaline in 15 adolescent girls with CFS and 14 age- and sex-matched controls. Dexamethasone inhibits T-cell proliferation in healthy controls and in CFS patients. However, the maximal effect of dexamethasone on T-cell proliferation is significantly reduced in CFS patients as compared with controls. The beta2-adrenergic receptor agonist terbutaline inhibits tumor necrosis factor-alpha production and enhances interleukin-10 production by monocytes. Our data demonstrate that the capacity of a beta2-adrenergic agonist to regulate the production of these two cytokines is also reduced in CFS patients. We did not observe differences in baseline or CRH-induced cortisol and ACTH between CFS patients and controls. Baseline noradrenaline was similar in CFS and controls, whereas baseline adrenaline levels were significantly higher in CFS patients. We conclude that CFS is accompanied by a relative resistance of the immune system to regulation by the neuroendocrine system. Based on these data, we suggest CFS should be viewed as a disease of deficient neuroendocrine-immune communication.

Tracheal microvascular responses to beta-adrenergic stimulation in anesthetized rats.

Previous study of adrenergic control of the tracheal vasculature in rats (1) demonstrated that beta-adrenergic blockade heightened arteriolar and large venular contractile responses to norepinephrine, a nonselective alpha-adrenergic agonist. The present study was undertaken to confirm the presence of functional beta-adrenergic receptors and to determine which beta-adrenergic receptor subtypes mediate vasodilation in this tissue. Tracheal adventitial arterioles (12.0 to 47.0 micro m initial diameter, n=39) and venules (48.0 to 98.5 micrometers initial diameter, n=44) were observed through a video microscope, and vessel diameters were measured. Vessels were preconstricted with 10(-4) M phenylephrine (PHE), a selective alpha 1-adrenergic agonist, to achieve sufficient tone for measurement of dilation responses. When vessels were treated only with PHE, arterioles and venules constricted to 55.9% and 67.6% of their initial diameter, respectively, after 15 min of suffusion. When preconstricted vessels were treated with the nonselective beta-adrenergic agonist isoproterenol (10(-5) M), both arterioles and venules significantly dilated from 63.4% to 82.9% and from 71.5% to 81.3% of their initial diameters. At high concentration (10(-5) M), the putative beta 2-adrenergic agonist terbutaline also caused preconstricted arterioles and venules to significantly dilate from 70.8% to 79.8% and from 71.5% to 83.4% of their initial diameters. The selective beta 1-adrenergic antagonist atenolol (10(-6) M) did not affect terbutaline-induced dilation in preconstricted arterioles, but greatly attenuated dilation in preconstricted venules. From these data, we conclude that beta 2-adrenergic receptors are present in and mediate dilation of tracheal arterioles, and also, that the dilation in large tracheal venules is mediated in large part through beta 1-adrenergic receptors.

Changes of tension and [Ca2+]i during beta-adrenoceptor activation of single, intact fibres from mouse skeletal muscle.

beta-Adrenergic agonists increase tension production in fast-twitch skeletal muscle, but the underlying mechanism is unknown. In the present study we have exposed intact, single fibres from a mouse muscle to the beta 2-adrenergic agonist terbutaline. Fibres were stimulated to produce 350-ms tetani at 20-100 Hz while measuring the myoplasmic Ca2+ concentration ([Ca2+]i) and tension. The fluorescent indicator Indo-1 was used to measure [Ca2+]i. Application of terbutaline resulted in marked increases of both tetanic [Ca2+]i and tension. Terbutaline had no significant effect on myofibrillar function as judged from normal Ca2+ sensitivity and tension production at saturating [Ca2+]i. The rate of [Ca2+]i and tension decline during relaxation was not affected by terbutaline, thus indicating a normal function of the sarcoplasmic reticulum (SR) Ca2+ pumps. The effect of terbutaline developed gradually over 5-10 min when fibres were stimulated each minute; the full effect of terbutaline was also obtained after a 10-min rest period in terbutaline. The [Ca2+]i at rest was not affected by terbutaline. In conclusion, beta-adrenergic stimulation increases tetanic tension by enhancing SR Ca2+ release.

Alanine and Terbutaline in Treatment of Hypoglycemia in IDDM

To test the hypothesis that, in contrast to administration of glucose or glucagon, administration of the amino acid Ala or of the beta 2-adrenergic agonist terbutaline produces sustained glucose recovery from hypoglycemia. We developed a model of clinical hypoglycemia using subcutaneous injection of insulin (0.15 U/kg) in patients with IDDM. In comparison with nondiabetic subjects, patients with IDDM exhibited reduced glucagon (P = 0.0001), epinephrine (P = 0.0060), and pancreatic polypeptide (P = 0.0001) responses to hypoglycemia. In addition to placebos, the following were administered during hypoglycemia (2 h after insulin injection) in IDDM patients: oral glucose, 10 and 20 g; subcutaneous glucagon, 1.0 mg; oral Ala, 40 g; oral terbutaline, 5.0 mg; and subcutaneous terbutaline, 0.25 mg. Glucose (10 and 20 g) and glucagon raised plasma glucose (P = 0.0163, 0.0060, and 0.0001, respectively) from 3.0-3.3 mM to peaks of 5.4 +/- 0.4, 6.8 +/- 0.7, and 11.8 +/- 0.8 mM within 30, 45, and 60 min, respectively, but the responses were transient. Oral Ala raised glucose levels (P = 0.0401) to 4.0 +/- 0.4 mM within 30 min; glucose levels then rose gradually to a 6-h value of only 7.1 +/- 0.9 mM. Oral terbutaline raised glucose levels (P = 0.0294) to 4.3 +/- 0.3 mM within 30 min; glucose levels then rose substantially. In contrast, subcutaneous terbutaline raised glucose levels (P = 0.0249) to 3.7 +/- 0.1 mM within 15 min; the levels plateaued at 5.0 mM from approximately 60-150 min and then paralleled the placebo curve. Ala and terbutaline produce sustained glucose recovery from hypoglycemia in IDDM and are therefore potentially useful agents for the treatment of mild or moderate iatrogenic hypoglycemia, or the prevention of iatrogenic hypoglycemia, when food intake is not anticipated over the following several hours.

The β2-adrenergic agonist terbutaline suppresses acute passive transfer experimental autoimmune myasthenia gravis (EAMG)

Treatment of Lewis rats with the beta 2-adrenergic agonist terbutaline suppressed clinical symptoms of acute passive transfer EAMG induced with monoclonal anti-acetylcholine receptor antibody and accelerated clinical recovery in affected animals. Electrophysiological studies showed that the amplitude of the first compound muscle action potential was significantly larger in terbutaline-treated rats as compared to controls. In both groups, a comparable number of inflammatory cells at the muscle endplates was seen.

Effects of magnesium and terbutaline on contractility and K + uptake in isolated human uterine muscle

Mg++ (3 and 6 mmol/L), the beta 2-adrenergic agonist terbutaline (1 and 10 mumol/L), and dibutyryl cyclic adenosine 5'-monophosphate (0.1 and 1 mmol/L) suppressed spontaneous activity and the increase in contractile activity induced by ouabain or K(+)-free buffer in isolated human pregnant myometrium. The ouabain-suppressible rubidium 86 or potassium 42 uptake was unaffected by the presence of Mg++ (3 and 6 mmol/L), the beta 2-adrenergic agonist terbutaline (1 and 10 mumol/L), or dibutyryl cyclic adenosine 5'-monophosphate (1 mmol/L). However, loading of the strips with Na+ and incubation in high K+ induced a fivefold increase in rubidium 86 uptake. On the basis of these flux rates, our previous data on the total concentration of sodium-potassium pumps in the human myometrium, and an estimated maximum transport rate of the sodium-potassium pump of 8900 K+ ions per minute at 30 degrees C, it could be calculated that the sodium-potassium pump in the Na(+)-loaded strips reached around 80% of its maximal rate. Taken together, these results showed that the relaxant effects of Mg++, terbutaline, and dibutyryl cyclic adenosine 5'-monophosphate on human myometrium are not due to a stimulation of active sodium-potassium transport.

Adrenergic control of circulating lymphocyte subpopulations. Effects of congestive heart failure, dynamic exercise, and terbutaline treatment.

The current studies were undertaken to explore the relationship between enhanced sympathetic nervous activity and lymphocyte subset distribution in three settings: congestive heart failure, dynamic exercise, and beta-adrenergic agonist treatment. We compared the number and subset distribution of circulating lymphocytes in 36 patients with congestive heart failure and 31 age-matched control subjects. The number of circulating lymphocytes was lower in heart failure than in control. This was due to a reduction in Tsuppressor/cytotoxic and natural killer cells without significant alteration of Thelper cells. The extent of the alteration was similar in patients with idiopathic and ischemic heart failure, but the reduction was more pronounced in patients with New York Heart Association class III-IV than in class I-II. The plasma catecholamine elevation in heart failure was also independent of etiology but more pronounced in the more severely ill patients. We also assessed lymphocyte subsets after acute stimulation of sympathetic activity by dynamic exercise and after treatment with the beta-adrenergic agonist terbutaline. Dynamic exercise until exhaustion increased the number of circulating lymphocytes in healthy controls and heart failure patients in a subset-selective manner. By contrast, a 7-d treatment with terbutaline caused a reduction in the circulating number of lymphocytes in some subsets that was identical to that seen in heart failure patients. We conclude that prolonged sympathetic activity reduces the number of circulating lymphocytes by a beta-adrenergic mechanism. Such alterations might be involved in the pathophysiology of heart failure and other disease states involving increased activity of the sympathetic nervous system.

Adenosine 3′,5′-Monophosphate Analogs and β-Adrenergic Agonists Induce the Synthesis of the Major Surfactant Apoprotein in Human Fetal Lungin Vitro*

The use of beta-adrenergic agonists in the treatment of preterm labor has been found to be associated with a decreased incidence of respiratory distress syndrome (RDS) in premature newborns. beta-Sympathomimetic agents, which activate adenylate cyclase and increase tissue cAMP levels, as well as cAMP analogs stimulate surfactant glycerophospholipid synthesis and secretion by fetal lung tissue. In the present study, we used antibodies directed against the major human pulmonary surfactant apoprotein, a 35,000-dalton glycoprotein, to evaluate the effects of the cAMP analog dibutyryl cAMP (Bt2cAMP) and the beta-adrenergic agonist terbutaline on surfactant apoprotein synthesis in human fetal lung explants in organ culture. By use of immunoblot analysis, we found that Bt2cAMP (1 mM) markedly stimulated accumulation of the major surfactant apoprotein in human fetal lung explants, as did terbutaline. Bt2cAMP treatment also increased the relative rate of incorporation of [35S]methionine into the major surfactant apoprotein. The Bt2cAMP-induced increase in surfactant apoprotein synthesis and accumulation was associated with an increase in the levels of translatable surfactant apoprotein mRNA. Morphometric analysis at both the light and electron microscopic levels was used to evaluate the effects of Bt2cAMP on the morphology of the human fetal lung in vitro. After 48-h incubation with Bt2cAMP, the prealveolar ducts of the fetal lung explants were enlarged greatly, and the relative amount of interalveolar connective tissue was reduced compared to those in control tissues. The volume density of type II cells in the Bt2cAMP-treated explants was significantly greater than that in control explants at this time point; however, after 4 and 6 days of incubation, the volume density of type II cells in control and Bt2cAMP-treated tissues was similar, and the lumina of the prealveolar ducts of control tissues had a volume density similar to that of Bt2cAMP-treated explants. Bt2cAMP also had pronounced effects on the ultrastructural morphology of the human fetal lung explants. Large quantities of secreted lamellar bodies and tubular myelin were observed in the lumina of the prealveolar ducts of the Bt2cAMP-treated tissue. Few lamellar bodies and no tubular myelin were observed in the lumina of the prealveolar ducts of control tissues. These findings suggest that cAMP may serve an important regulatory role in the synthesis and secretion of the major surfactant apoprotein by human fetal lung.

Beta adrenergic influence on oesophageal peristalsis in man.

The effects of the beta-1 adrenergic agonist prenalterol and the beta-2 adrenergic agonist terbutaline on oesophageal peristalsis were studied in nine healthy volunteers with pressures recorded in the proximal, middle, and distal oesophagus. Two doses of the agonists were given after pretreatment with placebo, propranolol, or metoprolol in a double blind randomised fashion. Terbutaline 0.25 +/- 0.25 mg iv decreased peristaltic pressure in middle oesophagus from 8.1 +/- 1.1 to 5.1 +/- 0.8 kPa (p less than 0.01) and in the distal oesophagus from 9.5 +/- 1.0 to 4.7 +/- 0.6 kPa (p less than 0.001). Peristaltic velocity was decreased in the distal oesophagus after terbutaline from 3.3 +/- 0.2 cm/sec to 2.9 +/- 0.2 cm/sec (p less than 0.05). Prenalterol 1 mg iv was followed by a decrease of peristaltic pressure in the middle oesophagus from 10.2 +/- 1.3 to 7.7 +/- 1.1 kPa (p less than 0.01) and a decrease of peristaltic velocity in upper oesophagus from 3.6 +/- 0.2 to 3.3 +/- 0.1 cm/sec (p less than 0.05) while no significant changes were seen in the distal oesophagus. Pretreatment with the beta-1 blocker metoprolol 15 mg iv blocked the effects of prenalterol 1 mg iv but not the effects of terbutaline. Propranolol 10 mg iv blocked the effects of terbutaline on peristaltic pressure. After metoprolol infusion mean distal peristaltic amplitude was 11.9 +/- 0.8 kPa compared with 8.5 +/- 1.2 kPa after placebo (p less than 0.01). It is concluded that both beta-1 and beta-2 adrenoceptor stimulation significantly decrease oesophageal peristaltic pressure in man. The body of the oesophagus seems to be under beta adrenergic inhibitory influence under physiological conditions.

Serotonin-induced stimulation of progesterone production by cow luteal cells in vitro.

The addition of acetylcholine or histamine (10(-7) to 10(-4) M), gamma-aminobutyric acid, a dopamine agonist, and melatonin (10(-7) to 10(-5) M) did not alter basal or LH-stimulated progesterone production (P greater than 0.05). The addition of the specific beta 2-adrenergic agonist terbutaline and salbutamol did not significantly elevate progesterone production. Treatment of luteal cells with serotonin (5-HT), 10(-6) to 10(-4) M, increased the production of progesterone (P less than 0.05). This stimulated production was inhibited by the addition of mianserin (10(-5) M, a 5-HT antagonist; P less than 0.05). Isoproterenol (10(-7) to 10(-4) M) also resulted in significant increases in progesterone production (P less than 0.05). The combined treatments of 5-HT + LH, isoproterenol + LH, or isoproterenol + 5-HT did not result in a further increase in progesterone above that observed in response to LH or isoproterenol alone (P greater than 0.05). The isoproterenol-induced progesterone production could not be blocked by butoxamine (10(-5) M, a beta 2-antagonist), or practolol (10(-5) M, a beta 1-antagonist), but was inhibited by propranolol (10(-5) M, a general beta-antagonist; P less than 0.05). The response to isoproterenol was unaffected by mianserin (10(-5) M). These results demonstrate a possible role for 5-HT in the regulation of steroidogenesis by the corpus luteum of the cow. Furthermore, these results suggest that serotonin-induced progesterone production is a receptor-mediated event.

Isolation and culture of human alveolar type II epithelial cells. Characterization of their phospholipid secretion.

Alveolar type II epithelial cells have been isolated previously from rodents but not from humans. The aims of this study were to isolate and culture alveolar type II cells from human lungs, and to study their phospholipid secretion. Lung tissue was obtained from 13 patients after lobectomy or pneumonectomy. Type II cells were isolated by a modification of our method for isolating rat type II cells with porcine pancreatic elastase and discontinuous metrizamide density gradients. Cells were purified further by differential adherence and they were then cultured on an extracellular matrix prepared from bovine corneal endothelial cells. We obtained 1.3 to 4.8 X 10(6) cells per gram of tissue with cell viability on the day of isolation of 96 +/- 1% (mean +/- SE, n = 10). Type II cell purity, assessed by Papanicolaou stain on Day 1 in culture, was 84 +/- 4% (mean +/- SE) in 9 of the 13 experiments. In the remaining 4 experiments, the purity was less than 50%. Electron microscopy showed well-preserved ultrastructure. The cells, radiolabeled with 32Pi, secreted the phospholipids characteristic of pulmonary surfactant, primarily phosphatidylcholine (68%) and phosphatidylglycerol (12%). Phospholipid secretion was stimulated by tetradecanoyl phorbol acetate (4.5 times baseline) and by the beta adrenergic agonist terbutaline (2.0 times baseline), but not by the cholinergic agonist carbamylcholine chloride. In summary, human alveolar type II epithelial cells can be isolated from resected lung and maintained in culture, and they secrete the phospholipids characteristic of pulmonary surface active material.

Predominantly beta-adrenergic control of equine sweating

Single equine sweat glands were found to secrete for more than 1 h in vitro in response to pharmacologic secretagogues. The adrenergic agonists epinephrine and norepinephrine evoked maximal sweat rates of 2.0 nl X gland-1 X min-1. However, the concentration of norepinephrine (10(-5) M) required to evoke the maximal response was 10 times higher than that for epinephrine. Maximal sweat rates also were stimulated with the beta 2-adrenergic agonist terbutaline. This stimulation was blocked by the beta-adrenergic antagonist propranolol. Moderate sweating responses were also obtained with the alpha-adrenergic agonists phenylephrine and methoxamine, but these responses also were blocked by propranolol. Neither the muscarinic blocker atropine nor the alpha-adrenergic antagonist phentolamine inhibited any of the pharmacologically induced sweat responses. Unlike most other mammalian exocrine glands, cholinergic agonists were ineffective in stimulating sweat secretion. Therefore equine sweat glands apparently are under predominantly beta-adrenergic control.

Adrenergic stimulation of placental progesterone production.

Cells from term human placentas were maintained in culture, and progesterone production was monitored over 24 h. The beta 1-adrenergic receptor agonist dobutamine (10(-5) M) and the beta 2-adrenergic receptor agonist terbutaline (10(-5) M) increased progesterone production by 36 +/- 19% and 49 +/- 8% (+/- SE), respectively, compared with that in controls (P less than 0.001). Propranolol (10(-5) M) completely blocked the stimulatory effects of both drugs. The cAMP analog 8-bromo-cAMP (0.5 mM) also significantly altered (increased) progesterone production compared with controls (P less than 0.001), but this effect was not blocked to a significant degree by propranolol. The alpha-adrenergic receptor agonist methoxamine (10(-4) - 10(-6) M) did not significantly alter placental progesterone production compared with controls, and the stimulatory effect of terbutaline on progesterone production was not significantly affected by blockade of the alpha-adrenergic receptor with phentolamine. These data indicate that placental progesterone production can be significantly modulated by stimulation of beta-adrenergic, but not by alpha-adrenergic, receptors. This response may be mediated by increased intracellular cAMP. These findings may be important in considering other metabolic functions of the placenta as well as the treatment of preterm labor.

Stimulation of beta 2-adrenergic responsiveness by follicle-stimulating hormone in rat granulosa cells in vitro and in vivo.

The development of adrenergic responsiveness in ovarian granulosa cells cultured in the presence of androstenedione was investigated. Progesterone production by granulosa cells obtained from immature hypophysectomized diethylstilbestrol-treated rats was stimulated by FSH, but was only minimally affected by various adrenergic agents. In contrast, FSH treatment for 2 days in vivo or in vitro resulted in an increase in the adrenergic responsiveness of granulosa cells. Subsequent treatment with (-)epinephrine, (-)norepinephrine, or (-)isoproterenol (a potent beta-adrenergic agonist) resulted in time- and dose-dependent increases in progesterone production. The adrenergic agents enhanced the effects of hCG and PRL with respect to progesterone production, but were without effect on estrogen production or the maintenance of LH/hCG receptors in FSH-primed granulosa cells. A selective beta 2-adrenergic agonist (terbutaline) stimulated progesterone production in FSH-treated granulosa cells, whereas a beta 1-agonist (dobutamine) was 10,000-fold less effective. Furthermore, progesterone production induced by (-)epinephrine was blocked by a selective beta 2-antagonist (IPS 339), but the beta 1-antagonist (practolol) was 7,000-fold less effective. These results suggest that FSH treatment in vivo and in vitro increases beta 2-adrenergic responsiveness in ovarian granulosa cells and that this functional responsiveness is coupled to progesterone, but not to estrogen, biosynthesis.