Effects of inhibition of nitric oxide formation on basal vasomotion and endothelium-dependent responses of the coronary arteries in awake dogs

The role of nitric oxide in basal vasomotor tone and stimulated endothelium-dependent dilations in the coronary arteries in chronically instrumented awake dogs was studied by examining the consequences of inhibiting endogenous nitric oxide formation with the specific inhibitor of nitric oxide formation, NG-monomethyl-L-arginine (L-NMMA). In four awake dogs, coronary dimension crystals were chronically implanted on the circumflex artery for the measurement of epicardial coronary diameter, and Doppler flow probes were implanted for quantitation of phasic coronary blood flow (vasomotion of distal regulatory resistance vessels). Basal epicardial coronary diameter, acetylcholine-stimulated endothelium-dependent dilation, and flow-induced endothelium-dependent dilation of the epicardial arteries and phasic blood flow were recorded before, and after 5, 15, 50, and 120 mg/kg of L-NMMA. L-NMMA induced a dose-related increase in basal epicardial coronary vasomotor tone. There was an accompanying increase in aortic pressure and a decrease in heart rate. At doses greater than or equal to 50 mg/kg, rest phasic coronary blood flow was also decreased. Left ventricular end-diastolic pressure and contractility were not significantly changed. In contrast, the flow-induced or acetylcholine-stimulated endothelium-dependent responses were attenuated only after infusion of the highest does of L-NMMA (120 mg/kg). The changes in the basal vasomotor tone and acetylcholine-stimulated endothelium-dependent responses returned towards the control states in the presence of L-arginine (660 mg/kg). These data support the view that nitric oxide plays a significant role in modulating basal vasomotion and endothelial-dependent dilation stimulated by acetylcholine or increase in blood flow in epicardial coronary arteries and also influence the regulation of coronary blood flow during physiologic conditions.

Development and mechanism of a specific supersensitivity to nitrovasodilators after inhibition of vascular nitric oxide synthesis in vivo

The mechanism of the increased sensitivity to nitrovasodilators after removal of endothelial nitric oxide (NO) was investigated in vitro and in vivo. The vasoconstrictor potency of phenylephrine and the force of contraction of rat isolated aortic rings were significantly enhanced after endothelium removal or treatment with inhibitors of endothelial NO synthase. Furthermore, these procedures led to a significant decrease in the basal levels of cGMP in the vascular rings. Moreover, the potency of glyceryl trinitrate (n3Gro) and sodium nitroprusside (SNP) as relaxing agents and the ability of SNP to induce increases in cGMP in aortic rings were significantly enhanced in those rings denuded of endothelium or treated with the inhibitors. These procedures did not affect the vasodilator actions of isoprenaline or 8-bromo-cGMP. In the anesthetized rat, treatment with the inhibitors enhanced significantly the hypotensive responses to n3Gro without affecting those to isoprenaline. These data indicate that the removal of the basal NO-mediated vasodilator tone in the cardiovascular system leads, at the level of the soluble guanylate cyclase, to a specific supersensitivity to nitrovasodilators in vivo. The existence of such a phenomenon has important implications for understanding the local physiological control of blood flow, its pathological disturbances, and the mechanism of action of nitrovasodilators.

Nitric oxide and prostacyclin. Divergence of inhibitory effects on monocyte chemotaxis and adhesion to endothelium in vitro

Monocyte-endothelial interactions are of fundamental importance in determining the movement of monocytes from the blood stream into the vessel wall. This study reports that two endothelium-derived factors, nitric oxide and prostacyclin, alter in vitro monocyte behavior. Nitric oxide (greater than 10(-5) M) inhibited monocyte adhesion to porcine aortic endothelial cell monolayers, whereas prostacyclin (10(-9) to 10(-5) M) had no effect. Both nitric oxide and prostacyclin inhibited monocyte chemotaxis stimulated by N-formyl-methionyl-leucyl-phenylalanine and induced dose-dependent increases in intracellular cyclic guanosine monophosphate and cyclic adenosine monophosphate concentrations, respectively. The cell surface expression of the CD11b/CD18 adhesion receptor, a glycoprotein complex known to mediate monocyte intracellular adhesion, was not altered by either nitric oxide or by prostacyclin. Thus, endothelium-derived nitric oxide and prostacyclin may have a physiological role in modulating monocyte-vascular wall interactions. Alterations in this system may contribute to the increased monocyte emigration from the blood stream into the vessel wall observed in atherogenesis.

Identification of N-iminoethyl-L-ornithine as an irreversible inhibitor of nitric oxide synthase in phagocytic cells

1. The synthesis of nitric oxide (NO) from L-arginine by rat peritoneal neutrophils (PMN) and the murine macrophage cell-line J774 and the inhibition of this synthesis by N-iminoethyl-L-ornithine (L-NIO), NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine (L-NNA) and its methyl ester (L-NAME) were investigated. 2. L-NIO was the most potent inhibitor in both types of cells while L-NMMA was less active. L-NNA and L-NAME had no significant effect in PMN and L-NNA produced only approximately 40% inhibition of the generation of NO in the J774 cells at the highest concentration tested (300 microM). 3. The inhibitory effect of L-NIO was rapid in onset, requiring 10 min pre-incubation to achieve its full inhibitory activity, while the other compounds required 20-60 min pre-incubation to achieve their full effect. 4. The inhibitory effect of L-NIO (10 microM) on intact cells could not be reversed by L-arginine (300 microM) but could be prevented by concomitant incubation with this compound (300 microM), while the effect of the other inhibitors could be reversed by a 3-5 fold molar excess of L-arginine. 5. The NO synthase from both PMN and J774 cells was cytosolic and NADPH- but not Ca2(+)-dependent, with Km values for L-arginine of 3.3 +/- 0.8 and 4.2 +/- 1.1 microM respectively. 6. L-NIO was the most potent inhibitor of the neutrophil and J774 enzymes with IC50 values of 0.8 +/- 0.1 and 3 +/- 0.5 microM respectively. Furthermore, the effect of L-NIO was irreversible. The other three compounds were less potent, reversible inhibitors. 7. The inhibitory effects of all these compounds were enantiomerically specific. 8. These data indicate that L-NIO is a novel, potent, rapid in onset and irreversible inhibitor of NO synthase in phagocytic cells. The rapid uptake of L-NIO compared with the other compounds indicates that phagocytic cells have different uptake mechanisms for L-arginine analogues.

Dexamethasone prevents the induction by endotoxin of a nitric oxide synthase and the associated effects on vascular tone: an insight into endotoxin shock

The relationship between vascular tone and the induction by endotoxin of a nitric oxide (NO) synthase was studied in vitro in rings of rat thoracic aorta. In rings with and without endothelium there was a time-dependent induction of NO synthase accompanied by both spontaneous and L-arginine-induced relaxation and by reduced contractility to phenylephrine. These effects, which were attributable to the presence of endotoxin in the Krebs' buffer, were attenuated by cycloheximide, polymyxin B and inhibitors of NO synthase. Furthermore, dexamethasone inhibited the induction of NO synthase and the consequent effects on vascular tone. These findings indicate that prevention of the induction of NO synthase by glucocorticoids may be an important component of their therapeutic action.

Effects of the cyclo-oxygenase inhibitor, fenbufen, on clenbuterol-induced hypertrophy of cardiac and skeletal muscle of rats

1. When rats were fed with clenbuterol for 7 days skeletal muscle mass increased by 21% in the tonic soleus and phasic plantaris muscles and a 16% hypertrophy of the heart was also induced. Fenbufen, fed to rats for the same period, blocked the hypertrophy of the heart but not that of the skeletal muscles. 2. When feeding of fenbufen commenced 3 days before the administration of clenbuterol, plasma prosta-glandin F2 alpha (PGF2 alpha) was reduced by 79%; there was again no effect of fenbufen on clenbuterol-induced increases in the RNA or protein content of plantaris, nor in the increased area of fast or slow twitch fibres in the soleus. In the heart the clenbuterol-induced increases in the RNA (+21%) and protein content (+20%) were totally inhibited. 3. The effects of clenbuterol on heart muscle appear to be mediated by a cyclo-oxygenase metabolite of arachidonic acid whilst the effects on skeletal muscle are not.

The role of nitric oxide in mediating endothelium dependent relaxations in the human epicardial coronary artery

We have examined the ability of the endothelium of human epicardial coronary arteries to secrete vasorelaxant substances in response to pharmacological stimulation and under basal conditions. In addition, we have attempted to characterise the chemical identity and biochemical pathway for the synthesis of endothelial derived relaxing factor. Human epicardial coronary arteries were removed from patients who were undergoing heart transplantation for reasons other than ischaemic heart disease. Arteries were cut into segments and suspended in 5 ml organ baths containing a modified Tyrodes solution at 37 degrees C, and gassed with a mixture of 95% oxygen and 5% carbon dioxide. Substance P (10(-10) - 10(-7) M) elicited a dose-dependent relaxation of the coronary segments but this action of substance P was dependent upon an intact endothelium. The maximum response of substance P was equivalent to 89 +/- 8.5% of the maximum effect induced by 1 microgram/ml glyceryl trinitrate. This vasorelaxant effect of substance P was unaffected by the presence of 10(-6) M indomethacin. L-NG-monomethyl-arginine (10(-4) M), a specific inhibitor of formation of nitric oxide from L-arginine, antagonised the relaxations induced by substance P, decreasing the maximum response of substance P to 34 +/- 10.5% of the response to glyceryl trinitrate. Upon application, L-NG-monomethyl-arginine caused a further 23.1 +/- 3.0 increase in tension on preconstricted vessels. This increase in tension was reversed with the addition of L-arginine, but was unaffected by D-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucocorticoids inhibit the expression of an inducible, but not the constitutive, nitric oxide synthase in vascular endothelial cells

Vascular endothelial cells contain a constitutive nitric oxide (NO) synthase that is Ca2(+)-dependent. In addition, we have found that these cells express, after activation with interferon-gamma and lipopolysaccharide, an inducible Ca2(+)-independent NO synthase that is distinct from the constitutive enzyme. The generation of NO by this enzyme was detectable after a lag period of 2 hr, reached a maximum between 6 and 12 hr, and was maintained for the duration of the experiment (48 hr). The expression of the inducible NO synthase was inhibited by the protein synthesis inhibitor cycloheximide, a compound that had no direct effect on the activity of either of the two enzymes. Furthermore, hydrocortisone and dexamethasone, but not progesterone, inhibited the expression of the inducible enzyme, without directly affecting the activity of either enzyme, without directly affecting the activity of either enzyme. The effect of these steroids was inhibited in a concentration-dependent manner by cortexolone, a partial agonist of glucocorticoid receptors. Thus, the inhibition of the induction of an NO synthase by glucocorticoids is a receptor-mediated event involving the inhibition of the synthesis of mRNA for de novo synthesis of this enzyme. The induction of this NO synthase may contribute to the pathophysiology of immunologically based conditions. Furthermore, the inhibition of this induction by anti-inflammatory steroids may explain some of the therapeutic and adverse effects of these compounds.

Acute effects of corticosterone on tissue protein synthesis and insulin-sensitivity in rats in vivo

The effect of corticosterone treatment on the sensitivity of muscle protein synthesis to insulin infusion was assessed in post-absorptive young rats. To select the optimal time period for corticosterone treatment, protein synthesis was measured by injection of L-[2,6-3H]phenylalanine (1.5 mmol/kg body weight) 1, 4, 12 or 24 h after injection of corticosterone (5 mg/kg body wt.). Muscle protein synthesis was significantly decreased at 4 h and the effect was maximal by 12 h; liver protein synthesis was elevated at 12 h and 24 h. The dose-response of muscle protein synthesis to a 30 min infusion with 0-150 munits of insulin/h was then compared in rats pretreated with corticosterone (10 mg/100 g body wt.) or vehicle alone. When no insulin was infused, corticosterone inhibited protein synthesis in gastrocnemius muscle. High doses of insulin stimulated protein synthesis, but the inhibition by corticosterone was similar to that in the absence of insulin. At intermediate doses of insulin there was an increased requirement for insulin to elicit an equivalent response in muscle protein synthesis. Plantaris muscle responded in a manner similar to that of gastrocnemius, but neither soleus muscle nor liver responded significantly to insulin. These data suggest that corticosterone has two modes of action; one which is independent from and opposite to that of insulin, and a second which causes insulin-resistance through a decrease in sensitivity rather than a change in responsiveness.

Characterization of three inhibitors of endothelial nitric oxide synthase in vitro and in vivo

1. Three analogues of L-arginine were characterized as inhibitors of endothelial nitric oxide (NO) synthase by measuring their effect on the endothelial NO synthase from porcine aortae, on the vascular tone of rings of rat aorta and on the blood pressure of the anaesthetized rat. 2. NG-monomethyl-L-arginine (L-NMMA), N-iminoethyl-L-ornithine (L-NIO) and NG-nitro-L-arginine methyl ester (L-NAME; all at 0.1-100 microM) caused concentration-dependent inhibition of the Ca2(+)-dependent endothelial NO synthase from porcine aortae. 3. L-NMMA, L-NIO and L-NAME caused an endothelium-dependent contraction and an inhibition of the endothelium-dependent relaxation induced by acetylcholine (ACh) in aortic rings. 4. L-NMMA, L-NIO and L-NAME (0.03-300 mg kg-1, i.v.) induced a dose-dependent increase in mean systemic arterial blood pressure accompanied by bradycardia. 5. L-NMMA, L-NIO and L-NAME (100 mg kg-1, i.v.) inhibited significantly the hypotensive responses to ACh and bradykinin. 6. The increase in blood pressure and bradycardia produced by these compounds were reversed by L-arginine (30-100 mg kg-1, i.v.) in a dose-dependent manner. 7. All of these effects were enantiomer specific. 8. These results indicate that L-NMMA, L-NIO and L-NAME are inhibitors of NO synthase in the vascular endothelium and confirm the important role of NO synthesis in the maintenance of vascular tone and blood pressure.

Characterization of the L-arginine:nitric oxide pathway in human platelets

1. The activation of the L-arginine: nitric oxide (NO) pathway during aggregation of human platelets by adenosine 5'-diphosphate (ADP), arachidonic acid, thrombin and the calcium ionophore A23187 and its inhibition by NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME) and N-iminoethyl-L-ornithine (L-NIO) were studied. The inhibition of the cytosolic platelet NO synthase by these compounds was also examined. 2. Platelet aggregation induced by ADP (1-10 microM) and arachidonic acid (0.1-10 microM), but not that induced by thrombin (1-30 mu ml-1) or A23187 (1-10 nM), was inhibited by L-, but not D-arginine (1-30 microM). However, in the presence of a subthreshold concentration of prostacyclin (0.1 nM) or of M & B 22948 (1 microM), a selective inhibitor of guanosine 3':5'-cyclic monophosphate (cyclic GMP) phosphodiesterase, L-arginine caused concentration-dependent inhibition of aggregation induced by all of these aggregating agents. 3. L-NMMA, L-NAME and L-NIO (all at 1-30 microM), but not their D-enantiomers, enhanced to the same extent platelet aggregation induced by ADP, arachidonic acid and thrombin without affecting that induced by A23187. 4. In the presence of 300 microM L-arginine, the NO synthase in platelet cytosol was inhibited by L-NMMA, L-NAME and L-NIO with IC50s of 74 +/- 9, 79 +/- 8 and 8.5 +/- 1.5 microM (n = 3), respectively. 5. These results indicate that the L-arginine: NO pathway in human platelets plays a role in the modulation of platelet aggregation.

The crucial role of physiological Ca2+ concentrations in the production of endothelial nitric oxide and the control of vascular tone

1. The effect of varying the extracellular Ca2+ concentration on the basal and acetylcholine (ACh)-induced release of nitric oxide (NO) from the rabbit aorta was investigated by use of a superfusion bioassay system. 2. Changes between 0.5 and 2.0 mM in the concentration of Ca2+ superfusing the detector bioassay tissues or perfusing endothelium-denuded donor aortae had no effect on the tone of these tissues. 3. Increasing the concentration of Ca2+ perfusing endothelium-containing donor aortae from zero to 1.25 mM caused a transient (24 +/- 9 min), concentration-dependent basal release of NO, which was attenuated at higher concentrations of Ca2+ (1.5-2.0 mM). 4. The duration of the effect of Ca2+ on the basal release of NO was increased by a concomitant infusion of L-arginine (100 microM) through the donor aorta. 5. Changes in the concentration of Ca2+ between 0.5 and 2.0 mM had a similar biphasic effect on the release of NO induced by ACh, which was also maximal at 1.25 mM Ca2+. 6. When Ca2+ was removed from the Krebs buffer perfusing the donor aorta, the basal release of NO declined within 2 min. In contrast, the release of NO induced by ACh declined progressively over 60 min. 7. Thus changes in the concentration of Ca2+ around the physiological range modulate the synthesis of NO by the vascular endothelium and consequently, vascular tone. This may account for the effects of dietary Ca2+ supplements on the control of some hypertensive states.

Inhibitors of phospholipase A2 block the stimulation of protein synthesis by insulin in L6 myoblasts

Insulin at a concentration close to the physiological range (100 mu-units/ml) stimulated protein synthesis in L6 myoblasts by 17%. Pre-treatment with the phospholipase A2 inhibitors mepacrine or dexamethasone prevented this stimulation and decreased the release of prostaglandin F2 alpha, implicating the action of phospholipase A2 and the subsequent metabolism of arachidonic acid to prostaglandins in the stimulation of protein synthesis by physiological doses of insulin. Higher concentrations of insulin (500-1000 mu-units/ml) stimulated protein synthesis in the presence of mepacrine or dexamethasone, suggesting that an alternative pathway may become important in insulin action when phospholipase A2 is inhibited.

Regional haemodynamic changes during oral ingestion of NG-monomethyl-L-arginine or NG-nitro-L-arginine methyl ester in conscious Brattleboro rats

Homozygous Brattleboro (i.e. vasopressin-deficient) rats were chronically instrumented with pulsed Doppler probes and intravascular catheters to permit continuous monitoring of regional haemodynamics. Over a 9 h period, rats drinking water showed no systematic changes in heart rate or mean arterial blood pressure although renal, mesenteric and hindquarters vascular conductances fell. These changes showed diurnal rhythms, probably related to the nocturnal habits of rats. In separate groups of animals spontaneous oral ingestion of NG-monomethyl-L-arginine (L-NMMA; 1 mg ml-1) or NG-nitro-L-arginine methyl ester (L-NAME; 0.1 mg ml-1) caused marked hypertension but no significant bradycardia. Compared to control animals, rats drinking L-NMMA for 9 h showed significantly greater mesenteric and hindquarters vasoconstrictions, and rats drinking L-NAME showed greater vasoconstrictions in all 3 vascular beds.

'Failure to thrive' in the elderly: diagnosis and management

"Failure to thrive" (FTT) is a term used to describe a gradual decline in physical and/or cognitive function of an elderly patient, usually accompanied by weight loss and social withdrawal, that occurs without immediate explanation. Both age-related and sociodemographic factors predispose the elderly to FTT. The most common etiologies are dementia, depression, delirium, drug reactions, and a few chronic diseases. The diagnostic evaluation of patients with FTT includes a review of the patient's activities of daily living, cognitive function, and mood; a targeted history and physical examination; and selected laboratory studies. Early recognition and management of FTT can reduce the risk of further functional deterioration, hospitalization, or nursing home placement.

An L-arginine/nitric oxide pathway present in human platelets regulates aggregation

Aggregation of human washed platelets with collagen is accompanied by a concentration-dependent increase in cyclic GMP but not cyclic AMP. NG-Monomethyl-L-arginine (L-MeArg), a selective inhibitor of nitric oxide (NO) synthesis from L-arginine, reduces this increase and enhances aggregation. L-Arginine, which has no effect on the basal levels of cyclic GMP, augments the increase in this nucleotide induced by collagen and also inhibits aggregation. Both of these effects of L-arginine are attenuated by L-MeArg. The anti-aggregatory action of L-arginine is potentiated by prostacyclin and by M&B22948, a selective inhibitor of the cyclic GMP phosphodiesterase, but not by HL725, a selective inhibitor of the cyclic AMP phosphodiesterase. L-Arginine also inhibits platelet aggregation in whole blood in a similar manner, although the concentrations required are considerably higher. L-Arginine stimulates the soluble guanylate cyclase and increases cyclic GMP in platelet cytosol. This stimulation is dependent on NADPH and Ca2+ and is associated with the formation of NO. Both the formation of NO and the stimulation of the soluble guanylate cyclase induced by L-arginine are enantiomer specific and abolished by L-MeArg. Thus, human platelets contain an NO synthase which is activated when platelets are stimulated. The consequent generation of NO modulates platelet reactivity by increasing cyclic GMP. Changes in the activity of this pathway in platelets may have physiological, pathophysiological, and therapeutic significance.

Kinetic characteristics of nitric oxide synthase from rat brain

The relationship between the rate of synthesis of nitric oxide (NO) and guanylate cyclase stimulation was used to characterize the kinetics of the NO synthase from rat forebrain and of some inhibitors of this enzyme. The NO synthase had an absolute requirement for L-arginine and NADPH and did not require any other cofactors. The enzyme had a Vmax. of 42 pmol of NO formed.min-1.mg of protein-1 and a Km for L-arginine of 8.4 microM. Three analogues of L-arginine, namely NG-monomethyl-L-arginine, NG-nitro-L-arginine and NG-iminoethyl-L-ornithine inhibited the brain NO synthase. All three compounds were competitive inhibitors of the enzyme with Ki values of 0.7, 0.4 and 1.2 microM respectively.

Macrophage killing of Leishmania parasite in vivo is mediated by nitric oxide from L-arginine

Peritoneal macrophages from CBA mice incubated with rIFN-gamma are effective in killing the protozoal parasite Leishmania major in vitro. This leishmanicidal activity can be completely inhibited by L-NG-monomethyl arginine (L-NMMA), a specific inhibitor of the L-arginine:nitric oxide (NO) pathway. The culture supernatants of macrophage activated by IFN-gamma contain increased levels of NO2-, the production of which is inhibited by L-NMMA, but not by its D-enantiomer. L. major promastigotes are killed when incubated at room temperature in PBS containing NO. These data demonstrate that NO is an effector mechanism in macrophage killing of intracellular protozoa. The importance of NO in vivo is demonstrated by the finding that CBA mice infected with L. major developed exacerbated disease when L-NMMA was injected into the lesions, resulting in 10(4)-fold increases in the number of parasites extractable from the lesions.

Macrophage killing of Leishmania parasite in vivo is mediated by nitric oxide from L-arginine

Peritoneal macrophages from CBA mice incubated with rIFN-gamma are effective in killing the protozoal parasite Leishmania major in vitro. This leishmanicidal activity can be completely inhibited by L-NG-monomethyl arginine (L-NMMA), a specific inhibitor of the L-arginine:nitric oxide (NO) pathway. The culture supernatants of macrophage activated by IFN-gamma contain increased levels of NO2-, the production of which is inhibited by L-NMMA, but not by its D-enantiomer. L. major promastigotes are killed when incubated at room temperature in PBS containing NO. These data demonstrate that NO is an effector mechanism in macrophage killing of intracellular protozoa. The importance of NO in vivo is demonstrated by the finding that CBA mice infected with L. major developed exacerbated disease when L-NMMA was injected into the lesions, resulting in 10(4)-fold increases in the number of parasites extractable from the lesions.

Control of regional blood flow by endothelium-derived nitric oxide

The regional hemodynamic consequences of inhibiting vascular endothelial nitric oxide generation with NG-monomethyl-L-arginine (L-NMMA) were studied in conscious Long-Evans rats. Experiments were carried out in groups of chronically instrumented rats with intravascular catheters and pulsed Doppler probes to monitor regional blood flow. L-NMMA (0.3-300 mg/kg) caused a dose-dependent, long-lasting (5-90 minutes), and enantiomerically specific increase in mean blood pressure and also caused bradycardia. The increase in blood pressure was accompanied by a dose-dependent and long-lasting vasoconstriction in the internal carotid, mesenteric, renal, and hindquarters vascular beds that could be attenuated, in a concentration-dependent manner, by L-arginine but not by D-arginine. In contrast, L-arginine did not affect the pressor or vasoconstrictor effects of vasopressin. These results indicate that nitric oxide production by vascular endothelial cells contributes to the maintenance of blood pressure and to the control of the resting tone of different vascular beds in the conscious rat.

Ambulatory management of urinary incontinence in the frail elderly

Urinary incontinence is a common problem in the ambulatory frail elderly population. An evaluation of the incontinent patient, performed in the physician's office, can suggest an etiology and appropriate therapies. Behavioral therapies, patient and caregiver education, environmental supports, and a few carefully selected medications can help these frail patients to control incontinence and improve their quality of life.

Role of endothelium-derived relaxing factor in regulation of renal hemodynamic responses

An endothelium-derived relaxing factor (EDRF) has recently been identified as nitric oxide (NO), originating from endothelial cell metabolism of L-arginine. In vitro studies suggest that EDRF/NO stimulates soluble guanylate cyclase and increases guanosine 3',5'-cyclic monophosphate (cGMP) levels in vascular smooth muscle cells, resulting in the vasorelaxant effects of endothelium-dependent vasodilators such as acetylcholine (ACh). The importance of EDRF/NO in normal physiology or disease states remains uncertain. We therefore investigated the relationship between ACh-induced hemodynamic responses, synthesis of EDRF/NO, and changes in the rate of urinary cGMP excretion in the anesthetized rat in vivo. Intravenous infusion of ACh resulted in hypotension, maintenance of glomerular filtration rate, and renal vasodilatation. ACh induced a dose-dependent increase in urinary cGMP excretion, an effect that was not observed with equihypotensive doses of the endothelium-independent vasodilator, prostacyclin. Rates of cGMP excretion were significantly correlated with the fall in systemic blood pressure induced by ACh. Treatment with NG-monomethyl-L-arginine (L-NMMA), an inhibitor of enzymatic synthesis of nitric oxide from L-arginine, prevented the ACh-induced increase in urinary cGMP excretion as well as the systemic and renal hemodynamic effects of ACh. Plasma levels of atrial natriuretic peptide were unchanged by ACh infusion. Intravenous infusion of L-NMMA was associated with increased blood pressure and decreased basal rates of urinary cGMP excretion. This hypertensive effect was reversed by administration of L-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinical and microbiological comparison of the effects of water and 0.02% chlorhexidine as coolants during ultrasonic scaling and root planing

The maxillary teeth of 10 patients with moderately advanced chronic periodontitis were treated in a split-mouth design study. The baseline examination included plaque and bleeding scores, probing depths and probing attachment levels. 2 sites in each quadrant were selected for dark-field microscopic analysis. Each quadrant was randomly assigned to test or control and instrumented with an ultrasonic scaler using either 0.02% chlorhexidine or water as the coolant. Measurements were repeated 2, 6 and 10 weeks later, together with additional plaque sampling. Ultrasonic instrumentation with either chlorhexidine or water was equally effective in reducing bleeding scores and improving probing attachment levels. 42% of chlorhexidine- and 38.7% of water-treated sites showed gains of 1 mm or more in clinical attachment. Mean reductions in probing depth were similar (0.9 mm chlorhexidine, and 0.8 mm water). At the final examination, the chlorhexidine-treated quadrants had significantly more sites with probing depths in the 1-3 mm category and less in the greater than 3 mm category than the control quadrants (P less than 0.05). Both treatments reduced the microscopic counts of motiles and spirochaetes, resulting in a subgingival microbiota consistent with periodontal health. The results indicate that chlorhexidine has a slight adjunctive effect in the reduction of pocket depth when used as a coolant during ultrasonic root planing for the treatment of chronic periodontitis.

Dexamethasone-induced catabolism and insulin resistance in L6 myoblasts are reversed by the removal of serum

1. One hundred nanomolar dexamethasone reduced protein synthesis by 16% and also decreased the accretion of protein and RNA in L6 myoblasts when foetal calf serum was present; these effects were reversed when serum was omitted from the medium. 2. Insulin (100 microU/ml) increased protein synthesis, protein accretion and RNA accretion both in the presence and the absence of serum. 3. Dexamethasone inhibited the effects of 100 microU insulin/ml in the presence of serum and induced insulin resistance; in the presence of 25 or 100 nM dexamethasone insulin was ineffective at concentrations below 250 microU and 1 mU/ml respectively.

Nitric oxide from L-arginine stimulates the soluble guanylate cyclase in adrenal glands

The formation of nitric oxide (NO) by an L-arginine:NO synthase and its stimulation of the soluble guanylate cyclase was studied in rat whole adrenal and bovine cortex and medulla cytosol. In the presence of L-arginine, the stimulation of soluble guanylate cyclase was accompanied by the formation of citrulline and NO2-, formed from NO. The NO synthase was NADPH- and Ca(2+)-dependent and was inhibited by several L-arginine analogues. These results indicate that rat and bovine adrenal cytosol contains an L-arginine:NO synthase.

NG-monomethyl-L-arginine does not inhibit the hindquarters vasodilator action of endothelin-1 in conscious rats

Regional haemodynamic responses to endothelin-1 were assessed in conscious, unrestrained Long Evans rats, chronically instrumented with pulsed Doppler flow probes. Bolus injection of endothelin-1 (0.04 nmol) caused an early transient hypotension and increase in hindquarters vascular conductance. In the presence of NG-monomethyl-L-arginine (L-NMMA), which inhibits endothelial cell nitric oxide production, the hindquarters vasodilator response to endothelin-1 was unchanged and similar to that seen in the presence of vasopressin when the latter was infused to simulate the pressor effects of L-NMMA. These results indicate that the hindquarters vasodilatation in response to endothelin-1 is not dependent upon release of nitric oxide from endothelial cells.

The cyclo-oxygenase inhibitors indomethacin and ibuprofen inhibit the insulin-induced stimulation of ribosomal RNA synthesis in L6 myoblasts

Insulin stimulated total RNA accretion and the incorporation of [3H]uridine into RNA in L6 skeletal-muscle myoblasts. Incorporation of uridine into the rRNA was measured after either separation of 18 S and 28 S rRNA species by agarose-gel electrophoresis or separation of dissociated 40 S and 60 S ribosomal subunits on sucrose density gradients. Both methods showed a stimulation by insulin of uridine incorporation into the RNA of the two subunits. Two non-steroidal anti-inflammatory drugs, indomethacin and ibuprofen, which inhibit the metabolism of arachidonic acid by the cyclo-oxygenase pathway, inhibited the insulin-induced accretion of total cellular RNA and the incorporation of uridine into the RNA of both ribosomal subunits. The effect of insulin was observed both by using a tracer dose of [3H]uridine (5 microM) and in the presence of a high concentration (1 mM) of uridine to minimize possible changes in intracellular precursor pools. Neither insulin nor indomethacin was found to affect the incorporation of uridine into the total intracellular nucleotide pool, or the conversion of uridine into UTP. The ability of inhibitors of arachidonic acid metabolism to prevent insulin-induced increases in RNA metabolism suggests that a prostaglandin or other eicosanoid is involved in the signal mechanism whereby insulin stimulates RNA synthesis.

NMDA receptor activation induces nitric oxide synthesis from arginine in rat brain slices

Activation of N-methyl-D-aspartate (NMDA) receptors in rat cerebellum leads to the release of endothelium-derived relaxing factor, now identified as nitric oxide (NO), a stimulator of soluble guanylate cyclase. L-NG-monomethylarginine (L-NMMA), which blocks NO synthesis from L-arginine in several tissues, including a crude synaptosomal preparation from brain, inhibited the elevation of cyclic GMP induced by NMDA in rat cerebellar slices. D-NMMA was ineffective. L-Arginine, but not its D enantiomer, augmented the response to NMDA and reversed the inhibition by L-NMMA. The results indicate that stimulation of NMDA receptors results in the activation of the enzyme which catalyzes the formation of NO from L-arginine.

The effect of dietary salt ingestion on blood pressure of old-old subjects. A double-blind, placebo-controlled, crossover trial

To study the effect of dietary salt restriction and supplementation on blood pressure of elderly subjects, we performed a randomized, placebo-controlled, double-blind, crossover trial. Seven healthy subjects living in a long-term care facility, with a mean age of 85 and normal to borderline-hypertensive blood pressures, completed a 16-week protocol. During the double-blind cycles, subjects consumed either a low sodium (43 mmol/day) or a high sodium diet (175 mmol/day) for four weeks supplemented with placebo or salt capsules, with crossover to the other diet. Sitting diastolic blood pressure was significantly lower during the low sodium diet (69.86 mmHg +/- 3.80 vs 78.71 mmHg +/- 3.99, P less than .01), with all subjects showing decreases. Supine plasma renin activity and plasma aldosterone were significantly lower during the high sodium diet. Both low and high sodium diets were well-tolerated by subjects. Symptomatic postural hypotension and hyponatremia were not observed. We conclude that old-old subjects with borderline hypertension demonstrate salt-dependent increases in blood pressure. Without additional supportive studies, however, these results should not be generalized to any specific cohort of elderly individuals.

The impact of the prospective payment system on the treatment of hip fractures in the elderly

A review of 386 Medicare patients with hip fractures admitted to a private, suburban, teaching hospital from 1981 through 1987 revealed that since the implementation of the prospective payment system in 1984, average hospital stays declined from 17.0 days to 12.9 days (24.1%). Although the mean number of physical therapy sessions declined from 11.1 to 9.8 (11.7%), the average number of treatments per day during the physical therapy phase actually increased from 1.2 before to 1.4 after the prospective payment system. The proportion of patients discharged to nursing homes remained the same (52.9% vs 53.6%); the proportion of patients remaining in a nursing home 6 months after hospital discharge did not differ significantly (22.6% vs 19.9%). Furthermore, there were no differences in the 6-month ambulation status. Total adjusted average hospital charges for the pre- and post-prospective payment system groups did not increase significantly ($7295 vs $7565). These findings do not support the contention that the quality of care provided Medicare patients with hip fractures has deteriorated in this hospital environment.

A comparison of antibody levels to Bacteroides gingivalis in serum and crevicular fluid from patients with untreated periodontitis

The levels of IgG antibody to Bacteroides gingivalis were measured in serum and sequential samples of crevicular fluid from healthy and diseased sites in patients with untreated periodontitis using ELISA. All subjects had detectable serum titres but there was a wide variation in titre between subjects. Moderate to strong correlations were found between serum and crevicular fluid levels of IgG. A statistically significant difference was observed between sequential samples of crevicular fluid. There was no difference in the level of specific IgG to B. gingivalis in crevicular fluid between healthy and diseased sites within the same individual.

Nitric oxide synthesized from L-arginine regulates vascular tone in the coronary circulation of the rabbit

1. The role of nitric oxide (NO) in the regulation of the vascular tone of the coronary circulation of the Langendorff-perfused rabbit heart was investigated. 2. NG-monomethyl-L-arginine (L-NMMA; 10-100 microM), a specific inhibitor of NO formation from L-arginine (L-Arg), but not its D-enantiomer (D-NMMA; 100 microM) produced a dose-related, sustained increase in the coronary perfusion pressure (CPP). In addition, L-NMMA inhibited the vasodilator responses of acetylcholine (ACh), unmasking in some instances its direct vasoconstrictor effect. These effects of L-NMMA were attenuated by L-Arg. 3. L-NMMA (10 and 30 microM), but not D-NMMA (30 microM), caused a long-lasting inhibition of NO formation which was reversed by L-Arg (30 and 100 microM), but not by D-Arg (100 microM). 4. This study indicates that the formation of NO from L-Arg in the coronary circulation of the rabbit plays a role both as a regulator of vascular tone and as a mediator of the vasodilatation induced by ACh.

Formation of nitric oxide from L-arginine in the central nervous system: a transduction mechanism for stimulation of the soluble guanylate cyclase

A soluble enzyme obtained from rat forebrain catalyzes the NADPH-dependent formation of nitric oxide (NO) and citrulline from L-arginine. The NO formed stimulates the soluble guanylate cyclase and this stimulation is abolished by low concentrations of hemoglobin. The synthesis of NO and citrulline is dependent on the presence of physiological concentrations of free Ca2+ and is inhibited by NG-monomethyl-L-arginine, but not by its enantiomer NG-monomethyl-D-arginine or by L-canavanine. L-Homoarginine, L-arginyl-L-aspartate, or L-arginine methyl ester can replace L-arginine as substrates for the enzyme. These results indicate that NO is formed from L-arginine in the brain through an enzymic reaction similar to that in vascular endothelial cells, neutrophils, and macrophages, adding support to our hypothesis that the formation of NO from L-arginine is a widespread transduction mechanism for the stimulation of the soluble guanylate cyclase.

Synthesis of nitric oxide from L-arginine by neutrophils. Release and interaction with superoxide anion

Stimulated rat peritoneal neutrophils release a platelet inhibitory factor with the pharmacological properties of NO. This release is inhibited by NG-monomethyl-L-arginine and L-canavanine, indicating that it occurs through a mechanism similar to that in vascular endothelial cells and macrophages. As the degree of stimulation increases, the factor released is progressively inactivated by concomitant release of superoxide anions.

Effect of timing and number of baseline blood pressure determinations on postural blood pressure response

We hypothesized that the blood pressure response to standing may depend on the method of establishing baseline blood pressure. Three hundred elderly subjects previously completed a postural blood pressure protocol with three supine baseline blood pressure readings obtained two minutes apart prior to standing. Comparison of the readings showed a significant drop between the first and the second (P less than .001) but not between the second and third supine systolic blood pressures. The difference between the first supine systolic blood pressure and the one minute standing blood pressure was significantly greater than that between the third supine systolic blood pressure and the one minute standing blood pressure (P less than .001). A second group was prospectively studied to determine whether the change in blood pressure after standing was greater if only a single baseline reading was taken rather than multiple readings, and whether the decline in blood pressure over three readings was related to duration supine or to the number of blood pressures taken. This group also demonstrated a decline in systolic blood pressure with three serial readings. We conclude that supine blood pressure declines significantly between the first and second readings taken two minutes apart and is secondary to the repetition of readings and not the duration supine. However, this change in supine blood pressure does not significantly alter the blood pressure response to standing. Thus, it appears that a single baseline supine blood pressure measurement is adequate for determining the postural blood pressure response, and that pooling of multiple baseline readings may not be appropriate.

Role of endothelium-derived nitric oxide in the regulation of blood pressure

The role of endothelium-derived nitric oxide in the regulation of blood pressure in the anesthetized rabbit was studied with N omega-monomethyl-L-arginine (L-NMMA), a specific inhibitor of its formation from L-arginine. L-NMMA (3-100 mg.kg-1), but not its D-enantiomer, induced a dose-dependent long-lasting (15-90 min) increase in mean systemic arterial blood pressure. L-NMMA (100 mg.kg-1) also inhibited significantly the hypotensive action of acetylcholine, without affecting that of glyceryl trinitrate. Both these actions of L-NMMA were reversed by L-arginine (300 mg.kg-1), but not by D-arginine (300 mg.kg-1), indomethacin (1 mg.kg-1), prazosin (0.3 mg.kg-1), or by vagotomy. The effects of L-NMMA in vivo were associated with a significant inhibition of the release of nitric oxide from perfused aortic segments ex vivo. This inhibition was reversed by infusing L-arginine through the aortic segments. These results indicate that nitric oxide formation from L-arginine by the vascular endothelium plays a role in the regulation of blood pressure and in the hypotensive actions of acetylcholine.

Evidence that the hypertrophic action of clenbuterol on denervated rat muscle is not propranolol-sensitive

1. The effect of propranolol on the clenbuterol-induced protein anabolism in innervated and denervated soleus and plantaris muscles of the rat was studied. 2. The response to the beta-agonist, clenbuterol, in both innervated and denervated muscles, was not significantly inhibited by the beta-antagonist, propranolol. 3. The results provide further evidence to suggest that the action of clenbuterol on skeletal muscle protein accretion may not be directly mediated by beta-adrenoceptors.

A specific inhibitor of nitric oxide formation from L-arginine attenuates endothelium-dependent relaxation

1. The role of L-arginine in the basal and stimulated generation of nitric oxide (NO) for endothelium-dependent relaxation was studied by use of NG-monomethyl L-arginine (L-NMMA), a specific inhibitor of this pathway. 2. L-Arginine (10-100 microM), but not D-arginine (100 microM), induced small but significant endothelium-dependent relaxations of rings of rabbit aorta. In contrast, L-NMMA (1-300 microM) produced small, endothelium-dependent contractions, while its enantiomer NG-monomethyl-D-arginine (D-NMMA; 100 microM) had no effect. 3. L-NMMA (1-300 microM) inhibited endothelium-dependent relaxations induced by acetylcholine (ACh), the calcium ionophore A23187, substance P or L-arginine without affecting the endothelium-independent relaxations induced by glyceryl trinitrate or sodium nitroprusside. 4. The inhibition of endothelium-dependent relaxation by L-NMMA (30 microM) was reversed by L-arginine (3-300 microM) but not by D-arginine (300 microM) or a number of close analogues (100 microM). 5. The release of NO induced by ACh from perfused segments of rabbit aorta was also inhibited by L-NMMA (3-300 microM), but not by D-NMMA (100 microM) and this effect of L-NMMA was reversed by L-arginine (3-300 microM). 6. These results support the proposal that L-arginine is the physiological precursor for the basal and stimulated generation of NO for endothelium-dependent relaxation.

Indomethacin inhibits the insulin-induced increases in RNA and protein synthesis in L6 skeletal muscle myoblasts

Rates of accretion of RNA and protein and rates of protein synthesis were measured in sub-confluent cultures of L6 myoblasts. Insulin (100 microU/ml) stimulated protein synthesis by 15% within 30 min and by 40% at two and six hours. By six hours insulin also increased the accretion of RNA (+15%). The cyclo-oxygenase inhibitor indomethacin did not reduce the basal rate of RNA or protein accretion in L6 cells but reduced the rate of protein synthesis by 16%. When added together with insulin, indomethacin inhibited the hormonally-stimulated rate of protein synthesis and also significantly reduced the accretion of RNA. Indomethacin still reduced the effects of insulin on protein synthesis when added to the cells two hours after the hormone. Synthesis of RNA measured by the incorporation of [3H]-uridine was also stimulated by insulin but was inhibited by indomethacin only when the drug was present throughout the incubation. Inhibition of protein synthesis by cyclo-oxygenase inhibitors may be the result of both a direct action on translational efficiency and an effect on RNA synthesis.

A novel citrulline-forming enzyme implicated in the formation of nitric oxide by vascular endothelial cells

An enzyme in homogenates of porcine vascular endothelial cells forms L-citrulline from L-arginine. This enzyme is soluble and NADPH-dependent. In addition, the enzyme is inhibited by NG-monomethyl-L-arginine, suggesting that it is involved in the formation of nitric oxide by vascular endothelial cells.