Pharmacologic evaluation of A23187-induced contractions of three distinct preparations of guinea pig lung parenchymal strips.

The present investigation examined the pharmacologic profiles of three distinct guinea pig lung parenchymal strips (LPS): intact LPS, denuded LPS (devoid of any lung pleura) and pleural surface strips. All three preparations responded similarly to increasing concentrations of KCl, whereas maximum contractile responses of the intact LPS and pleural surface strips to histamine, LTD4 and U46619, a thromboxane A2 mimetic, were significantly greater (P less than 0.001) than those elicited by the denuded LPS. Moreover, concentration-response curves for intact LPS and pleural surface strips to ovalbumin and ionophore A23187 challenges were equivalent to each other, which were significantly (P less than 0.001) higher in magnitude than that for the denuded LPS. The net contractile response of the denuded LPS to A23187 was significantly reduced by 35% in the presence of 1 x 10(-5) M A-64077, a 5-lipoxygenase inhibitor, and nearly abolished with the addition of 1 x 10(-6) M pyrilamine and 4 x 10(-6) M indomethacin. In contrast, the maximum contractile responses of the intact LPS and pleural surface strips were reduced by 40 and 30%, respectively, in the presence of all three inhibitors. On the other hand, morphometric analysis revealed that the density of mast cells in the smooth muscle of lung pleura was as high as that found in the bronchiolar area (2.35 +/- 0.31 vs. 2.62 +/- 0.28 per 0.05 mm2). In contrast, mast cells were scarcely identified in the alveolar parenchyma.(ABSTRACT TRUNCATED AT 250 WORDS)     

旋磁场拮抗脑缺血再灌注损伤中磷脂酶A2和内皮素作用的研究

探讨旋磁场对脑缺血再灌注大鼠磷脂酶Ａ２（ＰＬＡ２）和内皮素（ＥＴ）含量的影响。方法：用四血管阻断法造成大鼠全脑缺血３０分钟后，再灌注３０分钟，此时大鼠脑组织ＰＬＡ２活性和脑组织、血浆ＥＴ的含量均显著提高，大脑皮层神经细胞和血脑屏障超微结构明显损伤。在大鼠脑缺血３０分钟后再灌注开始时，用旋磁场〔０．０８Ｔ，２５００ｒ／ｍｉｎ）作用于双侧颈总动脉区２０分钟。结果：大鼠脑组织ＰＬＡ２活性和脑组织、血浆ＥＴ含量的增高明显受抑，神经细胞和血脑屏障超微结构的损害程度减轻。结论：旋磁场有抑制ＰＬＡ２活性和降低ＥＴ水平的作用，对脑缺血再灌注损伤有一定的防治作用。     

Differential inhibition of cholinergic and noncholinergic neurogenic contractions by 5-hydroxytryptamine1A receptor agonists in guinea pig ileum.

Previous studies have shown that 5-hydroxytryptamine1A (5-HT1A) receptors are localized only to a subset of myenteric neurons in guinea pig ileum; the purpose of this study was to determine the possible functional significance of this differential receptor localization. Nerve-mediated contractions of the longitudinal muscle, myenteric plexus of guinea pig ileum were studied in vitro. Contractions were evoked by single transmural electrical stimuli (0.5-msec duration, at 0.1 Hz; cholinergic) or trains of stimuli (10 or 20 Hz for 1 sec; noncholinergic; scopolamine, 1 microM present). The 5-HT1A agonist, 8-hydroxy-2-(n-dipropylamino)tetralin (DPAT), reduced cholinergic contractions by no more than 14% in the concentration range of 0.001 to 0.3 microM. At high concentrations (1 to 100 microM), DPAT inhibited longitudinal muscle, myenteric plexus contractions; the EC50 was 6 microM. 5-Hydroxytryptamine (5-HT) and 5-carboxamidotryptamine (5-CT) reduced longitudinal muscle, myenteric plexus contractions by a maximum of 35% and 24% at 100 and 30 microM, respectively. Spiperone and 1-(2-methoxyphenyl)-4-[4-(2-phthalimidobutyl]piperazine (NAN-190), two 5-HT1A receptor antagonists, did not block DPAT-induced inhibition of cholinergic contractions. DPAT (3, 10 and 30 microM) shifted histamine concentration-response curves to the right in an apparently competitive manner; Schild analysis yielded a pA2 of 5.2. DPAT (3, 10, 30 and 100 microM) also shifted bethanechol concentration-response curves to the right in an apparently competitive manner; Schild analysis yielded a pA2 of 5.5. These data indicate that DPAT blocks histamine and muscarinic receptors on longitudinal muscle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Viral infection induces dependence of neuronal M2 muscarinic receptors on cyclooxygenase in guinea pig lung.

Inhibitory M2 muscarinic receptors on parasympathetic nerve endings in the lungs decrease release of acetylcholine, inhibiting vagally induced bronchoconstriction. Neuronal M2 receptor function can be studied using selective agonists and antagonists such as pilocarpine and gallamine. In pathogen-free guinea pigs indomethacin (1 mg/kg) did not alter the effect of either gallamine or pilocarpine, thus in pathogen free animals neuronal M2 muscarinic receptors function independently of cyclooxygenase products. However, in guinea pigs infected with virus, (which causes temporary loss of M2 receptor function), and then allowed to recover for 8 wk (to allow recovery of M2 receptors), indomethacin prevented both gallamine's potentiation and pilocarpine's inhibition of vagally induced bronchoconstriction. This new effect of indomethacin was not blocked by the addition of a 5-lipoxygenase inhibitor, AA861. However, the selective COX II inhibitor, L-745,337, had the same effect as indomethacin. Since exposure to ozone also caused neuronal M2 receptors to become dependent upon cyclooxygenase the effects of viral infection are likely to be due to inflammation. Thus, despite apparent recovery of normal M2 receptor function after viral infection or ozone, linkage of these receptors is chronically altered such that they become largely dependent on the activity of COX II.     

Evidence that the P2x purinoceptor of the smooth muscle of the guinea pig vas deferens is an ATP4- receptor

In solutions containing Mg2+ and Ca2+, ATP is in equilibrium between the tetrabasic form (ATP4-) and its bidentate coordination complexes, i.e., MgATP2- and CaATP2-. We sought evidence to determine whether contractions of the smooth muscle of the guinea pig vas deferens to ATP are in response to ATP4- or its bidentate complexes. Contractions to ATP were elicited in seven modified Krebs-Henseleit solutions containing varied concentrations of free and total Mg2+ and Ca2+ to alter the concentration of ATP4- at given ATPtotal concentrations. As the concentration of Mg2+ increased the concentration of ATP required to stimulate contraction to an equivalent degree also increased. Regardless of the free or total Mg2+ and Ca2+ concentrations, response magnitude was generally correlated with [ATP4-]. This suggests that ATP4- is the agonist at the P2x purinoceptor of the guinea pig vas deferens. The potency of ATP4- is high; the threshold, occurring at approximately 1 nM ATP4-, is 1000-fold less than that for norepinephrine. The implications of ATP4- as agonist are discussed in relation to adenine nucleotide potency, metabolism and P2 purinoceptor classification.     

Evidence that blood ionized calcium can regulate serum 1,25(OH)2D3 independently of parathyroid hormone and phosphorus in the rat.

This study asks whether arterial blood ionized calcium concentration (Ca++) can regulate the serum level of 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] independently of serum phosphorus and parathyroid hormone (PTH). We infused either PTH (bovine 1-34, 10 U/kg body wt/h) or saline into awake and unrestrained rats for 24 h, through a chronic indwelling catheter. PTH raised total serum calcium and arterial blood ionized calcium, yet serum 1,25(OH)2D3 fell from 35 +/- 6 (mean +/- SEM, n = 10) with saline to 12 +/- 3 pg/ml (n = 11, P less than 0.005 vs. saline). To determine if the decrease in serum 1,25(OH)2D3 was due to the elevated Ca++, we infused PTH into other rats for 24 h, along with varying amounts of EGTA. Infusion of PTH + 0.67 micron/min EGTA reduced Ca++, and 1,25(OH)2D3 rose to 90 +/- 33 (P less than 0.02 vs. PTH alone). PTH + 1.00 micron/min EGTA lowered Ca++ more, and 1,25(OH)2D3 increased to 148 +/- 29 (P less than 0.01 vs. saline or PTH alone). PTH + 1.33 micron/min EGTA lowered Ca++ below values seen with saline or PTH alone, and 1,25(OH)2D3 rose to 267 +/- 46 (P less than 0.003 vs. all other groups). Thus, during PTH infusion lowering Ca++ with EGTA raised 1,25(OH)2D3 progressively. There were no differences in serum phosphorus concentration or in arterial blood pH in any group infused with PTH. The log of serum 1,25(OH)2D3 was correlated inversely with Ca++ in all four groups infused with PTH (r = -0.737, n = 31, P less than 0.001), and also when the saline group was included (r = -0.677, n = 41, P less than 0.001). The results of this study indicate that serum 1,25(OH)2D3 may be regulated by Ca++ independent of PTH and serum phosphorus levels in the rat. Since 1,25(OH)2D3 regulates gastrointestinal calcium absorption, there may be direct feedback control of 1,25(OH)2D3, by its regulated ion, Ca++.     

A chimeric receptor that selectively targets membrane-bound carcinoembryonic antigen (mCEA) in the presence of soluble CEA.

Chimeric T cell receptors with specificity for tumor-associated antigens are successfully used to target T cells to tumor cells. The efficacy of this approach, however, is reduced by soluble antigen that is frequently present in high serum concentrations. To overcome this situation, we constructed an anti-CEA chimeric receptor whose extracellular moiety is composed of a humanized single chain antibody fragment (scFv) derived from the anti-CEA mAb BW431/26 and the CH2/CH3 constant domains of human IgG. The intracellular moiety consists of the gamma-signaling chain of the human Fc epsilon RI receptor constituting a completely humanized chimeric receptor. After transfection, the humBW431/26 scFv-CH2CH3-gamma receptor is expressed as a homodimer on the surface of MD45 T cells. Co-incubation with CEA+ tumor cells specifically activates grafted MD45 T cells indicated by IL-2 secretion and cytolytic activity against CEA+ tumor cells. Notably, the efficacy of receptor-mediated activation is not affected by soluble CEA up to 25 micrograms/ml demonstrating the usefulness of this chimeric receptor for specific cellular activation by membrane-bound CEA even in the presence of high concentrations of CEA, as found in patients during progression of the disease.     

Secreted phospholipases A2, a new class of HIV inhibitors that block virus entry into host cells

Mammalian and venom secreted phospholipases A(2) (sPLA(2)s) have been associated with a variety of biological effects. Here we show that several sPLA(2)s protect human primary blood leukocytes from the replication of various macrophage and T cell-tropic HIV-1 strains. Inhibition by sPLA(2)s results neither from a virucidal effect nor from a cytotoxic effect on host cells, but it involves a more specific mechanism. sPLA(2)s have no effect on virus binding to cells nor on syncytia formation, but they prevent the intracellular release of the viral capsid protein, suggesting that sPLA(2)s block viral entry into cells before virion uncoating and independently of the coreceptor usage. Various inhibitors and catalytic products of sPLA(2) have no effect on HIV-1 infection, suggesting that sPLA(2) catalytic activity is not involved in the antiviral effect. Instead, the antiviral activity appears to involve a specific interaction of sPLA(2)s to host cells. Indeed, of 11 sPLA(2)s from venom and mammalian tissues assayed, 4 venom sPLA(2)s were found to be very potent HIV-1 inhibitors (ID(50) < 1 nM) and also to bind specifically to host cells with high affinities (K(0.5) < 1 nM). Although mammalian pancreatic group IB and inflammatory-type group IIA sPLA(2)s were inactive against HIV-1 replication, our results could be of physiological interest, as novel sPLA(2)s are being characterized in humans.     

Calcium dependency of prostaglandin E2 production in rat glomerular mesangial cells. Evidence that protein kinase C modulates the Ca2+-dependent activation of phospholipase A2

Calcium has been implicated as an important factor in prostaglandin production. Phospholipase A2, the enzyme believed to be rate limiting for prostaglandin synthesis, is stimulated by Ca2+; however, the levels of Ca2+ necessary to stimulate phospholipase A2 in cell-free systems are higher than levels achieved in intact cells in response to agonists that stimulate prostaglandin synthesis. We examined the calcium dependency of prostaglandin E2 (PGE2) synthesis in the glomerular mesangial cell. Vasopressin enhanced PGE2 synthesis by mechanisms independent of extracellular Ca2+ concentration. The Ca2+ concentration dependency of PGE2 production was established by rendering cells permeable with digitonin and clamping Ca2+ concentration at various levels. When cytosolic free Ca2+ concentration ([Ca2+]f) was set at levels equal to those measured after stimulation with vasopressin in the intact cell, the PGE2 production by the Ca2+-clamped permeabilized cells was approximately one-half of that obtained in nonpermeabilized cells stimulated with vasopressin. Since stimulation of mesangial cells with vasopressin increases protein kinase C activation as well as [Ca2+]f the effects on PGE2 production of protein kinase C activation with phorbol myristate acetate (PMA) were examined. When permeabilized cells were exposed to Ca2+ concentrations in the range of [Ca2+]f measured in cells treated with vasopressin the addition of PMA approximately doubled PGE2 production. No increase in PGE2 production was observed with PMA when Ca2+ concentration was fixed at basal levels of less than 100 nM. Ca2+-dependent acylhydrolase activity and PGE2 production were inhibited by calmodulin inhibitors, W-7 and compound 48/80. Thus, vasopressin-induced PGE2 production could be explained by a synergistic effect of protein kinase C activation together with an increase in [Ca2+]f. A synergistic action of Ca2+ and PMA on acylhydrolase activity could also be observed in nonpermeabilized cells where A23187 was used to increase [Ca2+]f. The effect of PMA was mimicked by another stimulant of protein kinase C, 1-oleoyl 2-acetylglycerol, albeit with lower potency. Neither PMA nor 1-oleoyl 2-acetylglycerol alone had any effect on acylhydrolase activity. Vasopressin, in the presence of GTP gamma S, stimulated phospholipase C in permeabilized cells when [Ca2+]f was fixed at less than 100 nM, without an associated increase in acylhydrolase activity. This evidence, together with inhibition of acylhydrolase activity with phospholipase A2 inhibitors, dibucaine and mepacrine, indicates that the primary acylhydrolase activity was due to phospholipase A2. The enhanced phospholipase A2 activity observed with protein kinase C activation when [Ca2+]f is increased may be related to phosphorylation of phospholipase A2 itself or phospholipase A2 modulatory proteins. These experiments demonstrate that both Ca2+ and protein kinase C play important roles in the regulation of phospholipase A2 and PGE2 synthesis.     

Evidence for a noradrenergic innervation to "atypical" beta adrenoceptors (or putative beta-3 adrenoceptors) in the ileum of guinea pig.

Indirect evidence suggests that beta-1 adrenoceptors in the guinea pig ileum are innervated but it has not been determined whether "atypical" beta adrenoceptors also receive a postganglionic sympathetic innervation. To answer this question, experiments were undertaken using electrical stimulation of para-arterial sympathetic neurons to evoke relaxation in isolated segments of guinea pig ileum. Tension was developed in the ileal segments by either transmural electrical field stimulation to evoke the cholinergic "twitch" response, or by histamine to produce a steady-state contracture. Para-arterial sympathetic nerve stimulation evoked a frequency-dependent inhibition of the twitch response which was blocked by guanethidine and restored by dexamphetamine, indicating typical noradrenergic transmission. In preparations contracted with histamine and pretreated with benextramine to block alpha adrenoceptors, para-arterial sympathetic nerve stimulation evoked frequency-dependent relaxations which were reduced in magnitude but not abolished by the following beta adrenoceptor antagonists: bromoacetylalprenololmenthane (1 microM) or a combination of ICI 118,551 (0.3 microM) and CGP 20712A (0.1 microM). Remaining responses were blocked by compounds exhibiting affinity for atypical beta adrenoceptors, (-)-alprenolol (3 microM) and nadolol (300 microM), as well as the agonist (-)-isoproterenol (10 microM; to saturate the atypical beta adrenoceptor). However, relaxations to papaverine were unaffected by these treatments. Experiments revealed that potential cotransmitters (ATP, neuropeptide Y and somatostatin) do not appear to play a detectable role in relaxations produced by para-arterial sympathetic nerve stimulation. The results demonstrate, for the first time, that atypical beta adrenoceptors in guinea pig ileum receive a noradrenergic innervation.     

Thromboxane A2 accounts for bronchoconstriction but not for platelet sequestration and microvascular albumin exchanges induced by fMLP in the guinea pig lung.

When injected i.v. to guinea pigs, the granulocyte secretagog N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) induces bronchoconstriction (BC), lung platelet sequestration and increased transendothelial albumin exchanges in lungs. We evaluated BC and the variations of the lung contents in radiolabeled platelets, erythrocytes and extravascular albumin, as measurements of platelet lung entrapment, reduction of lung blood volume and increase of transendothelial albumin exchanges, respectively. Trimetoquinol, a thromboxane A2 (TXA2)-endoperoxide receptor antagonist, inhibited BC and platelet entrapment by lungs induced by fMLP, but protection was nonspecific because it also suppressed BC by histamine. The specific TXA2 synthetase inhibitor/endoperoxide receptor antagonist ridogrel suppressed BC and reduced lung platelet entrapment, but failed to prevent the increase of extravascular albumin and the decrease of erythrocyte lung contents due to fMLP. Consequently, the fMLP-induced increase of vascular albumin exchanges and reduction of lung blood volume are TXA2-independent. Aspirin prevented BC, but failed to suppress lung platelet entrapment by fMLP, indicating that in vivo platelet activation is not TXA2-dependent, even though the levels of circulating TXB2, the stable metabolite of TXA2, were increased after fMLP concomitantly with that of 6-keto-prostaglandin (PG)F1 alpha, the stable metabolite of PGI2. The ridogrel-treated animals showed reduced blood level of TXB2 and increased levels of 6-keto-PGF1 alpha after fMLP challenge. Blocking the cyclooxygenase pathway with aspirin prevented ridogrel-induced protection against lung platelet sequestration after fMLP, supporting the concept that rechanneling of arachidonate metabolism toward protective prostaglandins accounts for protection by ridogrel.     

Effect of transport inhibitors and additional anti-HIV drugs on the movement of lamivudine (3TC) across the guinea pig brain barriers

To treat human immunodeficiency virus (HIV) within the central nervous system (CNS), levels of anti-HIV drugs in the brain must reach therapeutic concentrations. The ability of (-)-2'-deoxy-3'-thiacytidine (3TC; lamivudine) to cross the blood-brain and blood-cerebrospinal fluid (CSF) barriers, alone and in combination with additional nucleoside analogs, was investigated. The bilateral in situ guinea pig brain perfusion method, linked to high-performance liquid chromatography analyses, was used to examine 3TC uptake into brain and CSF simultaneously. The influence of transport inhibitors and additional nucleoside analogs on this uptake was investigated. 3TC movement across the blood-CSF barrier was examined in more detail by the isolated choroid plexus model. 3TC movement across the brain barriers and subsequent accumulation in the brain and CSF was low. However, 3TC uptake from blood into choroid plexus (a potential CNS target for HIV treatment) was significant, and was facilitated by a digoxin-sensitive transporter. Another transporter was identified, which removed 3TC from the choroid plexus. Abacavir, 2'3'-didehydro-3'deoxythymidine, and 3'-azido 3'-deoxythymidine did not interact with 3TC at either of the brain barriers to affect CNS concentrations of 3TC. However, a significant interaction between 3TC and 2'3'-dideoxyinosine was observed at the choroid plexus, and it may prove beneficial to select drug combinations where no such interaction is indicated.     

Ability of SK&F 104078 and SK&F 104856 to identify alpha-2 adrenoceptor subtypes in NCB20 cells and guinea pig lung.

Alpha-2 adrenoceptors were characterized in three tissue culture cell lines and in membrane homogenates of guinea pig lung via the ability of a series of alpha adrenoceptor antagonists to inhibit the binding of [3H]clonidine, [3H]UK-14,304 and [3H]rauwolscine. The cells studied included those known to possess receptors of alpha-2A (HT29) and alpha-2B (NG108-15) subtypes as well as the previously uncharacterized NCB20 cells. Correlation of the ability of the antagonists to inhibit [3H]clonidine or [3H]UK-14,304 binding did not identify alpha-2 adrenoceptor subtypes. On the other hand, correlation of antagonist affinities against [3H]rauwolscine binding showed HT29 cells and guinea pig lung to have similar characteristics (r = 0.911) as did NG108-15 and NCB20 cells (r = 0.985). These data suggest subtle differences in the binding of [3H]agonists and [3H]antagonists to the alpha-2 adrenoceptor, resulting in the failure of [3H]clonidine and [3H]UK-14,304 to recognize differences between alpha-2A and alpha-2B receptor subtypes. 6-chloro-9-[(3-methyl-2-butenyl)oxy]-3-methyl-1H-2,3,4,5-tetrahydro-3- benzazepine (SK&F 104078) did not differentiate between the alpha-2A and alpha-2B receptor subtypes. However, 2-vinyl-7-chloro-3,4,5,6-tetrahydro-4-methylthieno[(4,3,2ef] [3]benzazepine (SK&F 104856), which has similar selectivity in functional in vitro models, was about 35-fold more potent in displacing [3H]rauwolscine binding to the alpha-2B site. These data provide additional evidence that the functional subclassification of alpha-2 adrenoceptors based on sensitivity to SK&F 104078 and SK&F 104856 subdivides this receptor in a different manner than does the alpha-2A/alpha-2B subclassification scheme.     

Discrete role for cytosolic phospholipase A(2)alpha in platelets: studies using single and double mutant mice of cytosolic and group IIA secretory phospholipase A(2)

Among several different types of phospholipase A(2) (PLA(2)), cytosolic PLA(2) (cPLA(2))alpha and group IIA (IIA) secretory PLA(2) (sPLA(2)) have been studied intensively. To determine the discrete roles of cPLA(2)alpha in platelets, we generated two sets of genetically engineered mice (cPLA(2)alpha(-/-)/sPLA(2)-IIA(-/-) and cPLA(2)alpha(-/-)/sPLA(2)-IIA(+/+)) and compared their platelet function with their respective wild-type C57BL/6J mice (cPLA(2)alpha(+/+)/sPLA(2)-IIA(-/-)) and C3H/HeN (cPLA(2)alpha(+/+)/sPLA(2)-IIA(+/+)). We found that cPLA(2)alpha is needed for the production of the vast majority of thromboxane (TX)A(2) with collagen stimulation of platelets. In cPLA(2)alpha-deficient mice, however, platelet aggregation in vitro is only fractionally decreased because small amounts of TX produced by redundant phospholipase enzymes sufficiently preserve aggregation. In comparison, adenosine triphosphate activation of platelets appears wholly independent of cPLA(2)alpha and sPLA(2)-IIA for aggregation or the production of TX, indicating that these phospholipases are specifically linked to collagen receptors. However, the lack of high levels of TX limiting vasoconstriction explains the in vivo effects seen: increased bleeding times and protection from thromboembolism. Thus, cPLA(2)alpha plays a discrete role in the collagen-stimulated production of TX and its inhibition has a therapeutic potential against thromboembolism, with potentially limited bleeding expected.     

Inhibitory effect of FO-1561 (S-adenosyl-L-methionine sulfate tosylate) on phospholipase A2

The mechanism of the protective effect of FO-1561 (S-adenosyl-L-methionine sulfate tosylate) on mitochondria was investigated using rat heart muscle. FO-1561 stimulated CO2 production from palmitic acid in the mitochondria, indicating an increase in energy production. FO-1561 inhibited mitochondrial swelling induced by Ca2+ added exogenously or by addition of snake venom phospholipase A2. Moreover, FO-1561 inhibited phospholipase A2 activity directly. These results suggested that FO-1561 blocked mitochondrial swelling by inhibiting endogenous phospholipase A2 activity and so preventing decrease in palmitic acid oxidation.     

Effect of the phospholipase A2 inhibitors quinacrine and 7,7-dimethyleicosadienoic acid in isolated globally ischemic rat hearts.

Phospholipase A2 (PLA2) activity results in the formation of lysophospholipids and free fatty acids which may contribute to ischemic myocardial dysfunction. We evaluated the cardioprotective activity of two putative PLA2 inhibitors, quinacrine and 7,7-dimethyleicosadienoic acid (DEDA), in isolated globally ischemic rat hearts. Pretreatment with 1, 5 and 50 microM quinacrine before ischemia did not alter coronary flow but did cause significant cardiodepression. Twenty five minutes of global ischemia and 30 min of reperfusion caused severe myocardial dysfunction and lactate dehydrogenase release. Quinacrine significantly improved reperfusion contractile function and reduced lactate dehydrogenase release, indicative of cardioprotection. In contrast, 30 to 100 microM DEDA produced neither preischemic cardiodepression nor cardioprotective activity. PLA2 inhibition was inferred from measurements of the prostacyclin metabolite, 6-keto-prostaglandin F1 alpha in the coronary effluent and myocardial palmitoyl-lysophosphatidylcholine. Quinacrine and DEDA reduced both 6-keto-prostaglandin F1 alpha and palmitoyl-lysophosphatidylcholine by similar degrees. These results suggest that the cardioprotective activity of quinacrine is independent of PLA2 inhibition. A possible role of calcium inhibition was investigated in rat aortic smooth muscle strips. Norepinephrine-, KCl- and BAY K8644-induced contractions were antagonized in the presence of 5 and 50 microM quinacrine, but were unaffected by 30 to 60 microM DEDA. The ability of quinacrine to inhibit calcium was investigated further in cardiac ventricular myocytes. Measurement of mean whole cell calcium currents showed that quinacrine (5 microM) could inhibit this current up to 70%. Thus, these results suggest that quinacrine-induced cardioprotection may not be due to PLA2 inhibition, but may be related to calcium entry blocking activity.     

Studies on the effect of triton (WR-1339) on guinea pig tissues. I. Lipide chemistry of lung,liver, spleen,adrenals, and blood

Guinea pigs given three subcutaneous injections of triton WR-1339, 300 mg./kg., at 3 day intervals develop an intense lipemia as evidenced by marked increases in serum phospholipide, free cholesterol, ester cholesterol, neutral fat, and total fatty acids. The total fatty acid content of the lung, liver, and spleen, however, remains unchanged. No qualitative change in the fatty acids of the lung and liver from treated animals could be detected by the methods used. The injection of triton was found to diminish slightly the cholesterol content of the adrenal glands. The implications of these findings are discussed in relation to an understanding of the mechanism involved in the therapeutic action of triton in experimental tuberculosis.