C. Norman Gillis

Panax ginseng pharmacology: A nitric oxide link? ☆

Panax ginseng is used in traditional Chinese medicine to enhance stamina and capacity to cope with fatigue and physical stress. Major active components are the ginsenosides, which are mainly triterpenoid dammarane derivatives. The mechanisms of ginseng actions remain unclear, although there is an extensive literature that deals with effects on the CNS (memory, learning, and behavior), neuroendocrine function, carbohydrate and lipid metabolism, immune function, and the cardiovascular system. Reports are often contradictory, perhaps because the ginsenoside content of ginseng root or root extracts can differ, depending on the method of extraction, subsequent treatment, or even the season of its collection. Therefore, use of standardized, authentic ginseng root both in research and by the public is to be advocated. Several recent studies have suggested that the antioxidant and organ-protective actions of ginseng are linked to enhanced nitric oxide (NO) synthesis in endothelium of lung, heart, and kidney and in the corpus cavernosum. Enhanced NO synthesis thus could contribute to ginseng-associated vasodilatation and perhaps also to an aphrodisiac action of the root. Ginseng is sold in the U.S. as a food additive and thus need not meet specific safety and efficacy requirements of the Food and Drug Administration. Currently, such sales amount to over

Ginsenosides protect pulmonary vascular endothelium against free radical — induced injury☆

300 million annually. As public use of ginseng continues to grow, it is important for this industry and Federal regulatory authorities to encourage efforts to study the efficacy of ginseng in humans by means of appropriately designed double-blind clinical studies.

Reduction in rabbit serum and pulmonary angiotensin converting enzyme activity after subacute bleomycin treatment

We studied the actions of saponin (ginsenosides) from Panax ginseng on free radical-induced pulmonary endothelial injury which is manifest as reversal of the normal vasodilator response to acetylcholine in perfused, vasoconstricted lungs. 50 or 200 micrograms/ml ginsenosides prevented this injury response and also reduced the pulmonary edema which follows free radical injury but did not alter the normal ACh-induced vasodilation in intact lungs. In control perfused lungs preconstricted with U46619, the ginsenoside mixture or purified ginsenosides Rb1 and Rg1 caused vasodilatation. This effect was eliminated by 100 microM nitro-L-arginine, an inhibitor of nitric oxide synthase. In cultured bovine aortic endothelial cells, ginsenosides (10 micrograms/ml) stimulated the conversion of [14C]-L-arginine to [14C]-L-citrulline. These data indicate that GS may cause vasorelaxation and prevent manifestations of oxygen free radical injury by promoting release of nitric oxide.

β-Adrenergic receptor ligand binding by rabbit lung

Abstract We studied morphological and biochemical alterations in the lungs of rabbits treated subcutaneously with bleomycin (5 mg/kg) three times weekly for 28 days. This treatment produced morphologically evident pulmonary damage characterized by the appearance of ciliated alveolar epithelial cells and endothelial blebs. No change in pulmonary collagen content was evident. Rabbits treated with bleomycin had significantly less pulmonary angiotensin converting enzyme activity than control animals, although no alterations in lung DNA, protein, glycosaminoglycans or hydroxyproline (an index of collagen) were observed. Serum angiotensin converting enzyme activity decreased with repeated bleomycin administration and was reduced by 42, 48 and 65 per cent from control animals 2, 3 and 4 weeks, respectively, after the initiation of drug treatment. These data provide biochemical evidence that subacute bleomycin administration damages the pulmonary endothelium in the absence of fibrosis and can reduce the serum activity of angiotensin converting enzyme in rabbits.

Roles of platelet-activating factor and thromboxane in group B Streptococcus-induced pulmonary hypertension in piglets.

Abstract The β-adrenergic receptor antagonists, [ 14 C]propranolol and [ 3 H]dihydroalprenolol, and [ 3 H]dihydroergocryptine, an α-adrenergic receptor antagonist, were removed to the extent of 94, 84 and 78 per cent, respectively, from medium perfused through rabbit lung. Subcellular fractionation indicated that most (85–97 per cent) of the radiolabel was bound to particulate fractions of lung homogenates. Studies of [ 3 H]dihydroalprenolol binding to membrane preparation, in vitro , revealed the presence of high affinity ( K D = 0.5 nM) and high density (> 1 pmole/mg of protein) β-adrenergic-specific binding sites. Binding was stereospecific since (−)-propranolol was 250-fold more potent than (+)-propranolol in inhibiting the binding of [ 3 H]dihydroalprenolol.

Depression of Pulmonary Metabolic Function by Cardiopulmonary Bypass Procedures Increases Levels of Circulating Norepinephrine

ABSTRACT: Platelet-activating factor causes pulmonary hypertension, shock, hypoxemia, neutropenia, and increased pulmonary vascular permeability; some of its effects are due to thromboxane A2 release. Evidence for possible role of these mediators in the genesis of group B Streptococcus (GBS)-induced pulmonary hypertension was sought using specific receptor antagonists for PAF and thromboxane A2 (TxA2) in anesthetized, ventilated piglets (≤ 12 d of age; n = 22). Infusion of 1 × 108 GBS/kg/min for one hour resulted in a sustained and significant increase in pulmonary artery pressure (PPA) from 17 ± 1 to 35 ± 3 torr. Pretreatment with the TxA2 antagonist SQ 29548 (0.75 mg/kg intravenous), completely inhibited the effect of GBS on PPA. Pretreatment with either platelet-activating factor antagonists SRI 63072 (3 mg/kg intravenous) or SRI 63441 (1 mg/kg) did not affect the pulmonary hypertension due to GBS infusion. GBS-induced pulmonary hypertension could be reversed by SQ 29548; SRI 63072 did not affect PPA when administered to pigs with GBS-induced elevation in PPA. Inasmuch as prevention and reversal of GBS-induced pulmonary hypertension are accomplished with the TxA2 antagonist but not with PAF antagonists, these data suggest that TxA2, rather than PAF, is responsible for the early pulmonary hypertension in this model of neonatal GBS sepsis. Therefore, TxA2 antagonists may be clinically useful in treating pulmonary hypertension related to GBS sepsis.

Prolonged reduction in serum angiotensin converting enzyme activity after treatment of rabbits with bleomycin.

We measured plasma levels of endogenous norepinephrine radioenzymatically in mixed venous and arterial blood simultaneously sampled from anesthetized dogs before, during, and after 1 to 4 hours of total cardiopulmonary bypass (CPB) or 2 hours of left heart bypass. Prior to bypass, arterial levels of norepinephrine were 0.41 +/- 0.04 ng/ml and pulmonary extraction of norepinephrine was 25 +/- 3% (N = 20). During bypass, norepinephrine levels significantly increased from control to 1.41 +/- 0.15 (1 or 2 hours of CPB; N = 8) and 1.97 +/- 0.30 (3 or 4 hours of CPB; N = 8) or 0.97 +/- 0.29 (2 hours of left heart bypass) ng/ml. Restoration of normal pulmonary blood flow was associated with a rapid and significant decrease in arterial levels of norepinephrine, which, after 1 or 2 hours of CPB or 2 hours of left heart bypass, returned to levels obtained before bypass. However, arterial levels of norepinephrine remained higher than 1 ng/ml in the 3-hour recovery period after prolonged bypass. In these animals, pulmonary extraction of norepinephrine was significantly less than control. These data suggest that the lungs ability to remove norepinephrine is altered by CPB and that the severity of the alterations is directly related to pump time. The impairment in extraction allows higher than normal concentrations of norepinephrine to enter the arterial circulation and may contribute to systemic hypertension after bypass.

Captopril removal by rabbit lung in vivo.

Previous work from this laboratory (J. S. Lazo, J. D. Catravas, and C. N. Gillis, Biochem. Pharmacol. 30, 2577-2584, 1981; J. D. Catraveras, J. S. Lazo, and C. N. Gillis, J. Pharmacol. Exp. Ther. 217, 524-529, 1981) demonstrated that subacute bleomycin (BLM) administration (5 mg/kg) to rabbits three times weekly for 4 weeks produced a marked decrease in serum angiotensin converting enzyme (ACE) activity in addition to producing both morphological and biochemical evidence of pulmonary endothelial damage. In this work, the reversibility of the decreased serum ACE activity and the biochemical and morphological status of the pulmonary endothelium after a substantial drug-free period in rabbits was examined. Rabbits were injected sc three times weekly for 4 weeks with vehicle or BLM (5 mg/kg) and then maintained drug free for an additional 6 or 7 weeks. Serum ACE activity decreased over 60% during the BLM treatment but did not return to control levels at any time during the drug-free period. The pulmonary endothelium, however, appeared undamaged. No decrease in pulmonary ACE activity was detected either in vitro or in vivo nor was the single-pass pulmonary removal in vivo of [3H]norepinephrine and 5-[14C]hydroxytryptamine different between BLM-treated and control rabbits after the drug-free period. In addition, no evidence of pulmonary endothelial damage was observed by light and electron microscopy. Thus, reduction in serum ACE activity appears to be a durable reflection of BLM toxicity in rabbits that persists even in the absence of any detectable biochemical or morphologic endothelial injury.

Measurement of endothelial metabolic functions in vivo

Removal of [14C]captopril by the lungs of anesthetized rabbits was measured by the multiple indicator dilution technique. After coinjection of indocyanine green (ICG) and [14C]captopril into the jugular vein of anesthetized rabbits, serial blood samples were collected from the carotid artery and each was analyzed for its content of both substances. Percent removal (R) of captopril after its initial injection of 10 nmoles captopril/kg (calculated at the peak of the ICG outflow curve) was 40.2 +/- 2.5 (S.E.M.) and was significantly greater than R after a second injection of 10 nmoles captopril/kg (20.1 +/- 2.4) 1 hr later. Removal of 70 nmoles captopril/kg (5.8 +/- 3.0 after first injection, 6.4 +/- 2.2 after second injection) was significantly lower than R of 10 nmoles captopril/kg. During a single pulmonary passage of either dose of captopril, R was inversely related to the calculated fractional concentration of intravascular captopril. Pulmonary metabolism of the angiotensin converting enzyme (ACE) substrate [3H]benzoyl-Phe-Ala-Pro [( 3H]BPAP) was 70.1 +/- 1.7% in the absence of captopril, and was reduced significantly to 27.4 +/- 2.4% by 10 nmoles captopril/kg and 7.6 +/- 0.2% by 6 mumoles BPAP/kg. BPAP (6.4 +/- 0.6 mumoles/kg) significantly reduced R of the first and second injections of 10 nmoles captopril/kg but this effect was selective, since BPAP did not reduce pulmonary removal of [14C]serotonin. These data indicate that pulmonary removal of captopril in vivo is saturable and may primarily reflect binding of the drug to pulmonary endothelial ACE.

Free-Radical Mediated Actions on Endothelial Cells of the Intact Lung

Lung metabolic functions include the interaction of microvascular endothelium with blood-borne substances such as physiologically important amine, eicosanoid, and peptide hormones and drugs. This activity is mediated by endothelial transport systems and enzymes which either synthesize or degrade these substances. Because they can alter the hormone content of aortic blood, these functions play a role in homeostasis, and their disturbance has been implicated in the pathogenesis of several forms of lung injury and disease.Lung metabolic functions include the interaction of microvascular endothelium with blood-borne substances such as physiologically important amine, eicosanoid, and peptide hormones and drugs. This activity is mediated by endothelial transport systems and enzymes which either synthesize or degrade these substances. Because they can alter the hormone content of aortic blood, these functions play a role in homeostasis, and their disturbance has been implicated in the pathogenesis of several forms of lung injury and disease.Both steady-state infusion and single injection, multiple indicator dilution techniques have been applied to measure endothelial metabolic functions in the intact lung. Considerable progress has been made in development of mathematical models for the processes, and their application has been tested both under normal conditions and also when the lung is perturbed experimentally. Unique experimental challenges are presented by measurement of metabolic functions in vivo, when steadystate infusion techniques cannot be used because systemic toxicity could result. In this case, the bolus injection approach has been used, with some success, both in laboratory animals and man. Although major challenges remain, their solution is essential if we are to apply knowledge of endothelial cell function in vitro to understanding lung microvascular physiology and pathophysiology in the intact animal.