Heinz Lüllmann

Drug-Induced Phospholipidoses

This review deals with drug-induced lipidoses and the possible underlying mechanisms. A variety of drugs, widely differing in their main pharmacological actions, but closely resembling each other with respect to particular physiochemical properties, have been found to cause in animals and man cytological alterations that are reminiscent of the inherited lipid-storage diseases of man. Ultrastructurally, the alterations are characterized by multilamellated or crystalloid cytoplasmic inclusions, i.e., residual bodies resulting from an intralysosomal accumulation of polar lipids. Biochemically, some of the most severely affected tissues have been demonstrated to contain increased amounts of phospholipids and of the drug applied. All drugs hitherto found to induce such alterations are cationic amphiphilic (amphipathic) compounds; they possess a highly apolar ring system and a cationic hydrophilic side chain (e.g., triparanol, chloroquine, chlorzyclizine, 4,4′-diethylaminoethoxyhexestrol, chlorphentermine, ipri...

The binding of drugs to different polar lipids in vitro.

Abstract For evaluation of the physico-chemical basis underlying the drug-induced generalized lipid storage disease, the equilibrium distribution of radioactively labelled amphiphilic drugs between a water phase and liposomes was determined. Liposomes were prepared from sphingomyelin (SM), phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS); the extent of binding of the drugs occurred in increasing order SM ∼ PC

INTERDEPENDENCE OF ION TRANSPORT AND THE ACTION OF OUABAIN IN HEART MUSCLE

1 The influence of ouabain (0.4 μM) on contractile force and cellular Na and K concentrations was investigated in isolated left atria of the guinea‐pig at rest and at different beat frequencies. Simultaneously the binding of ouabain to the tissue was determined. 2 Strict dependence of rates of onset of positive iontropic action and of binding of ouabain on beat frequency are limited to conditions where no alterations of cellular Na and K concentrations occur. A correlation was observed between sodium flux per unit time and the development of positive inotropism and binding to the receptors of ouabain. 3 Ouabain exerts its positive inotropic effect without affecting the intracellular Na and K concentrations in spite of the fact that under these conditions even the majority of binding sites, i.e. Na‐K‐adenosine triphosphatases (Na‐K‐ATPases), are occupied by the drug. The positive inotropic effect may be explained by a ouabain‐induced conformational alteration of the Na‐K‐ATPase which leads to structural alterations of the plasmalemma connected with an increased availability of coupling calcium. 4 Increasing the frequency of stimulation over a critical value, which appears to be determined by an overloading of the Na pump, induces a decrease in contractile force, cellular accumulation of Na and loss of K, and eventually contracture. 5 The rate of binding of ouabain appears to depend on the actual concentration of particular conformations of the Na‐K‐ATPase with high affinity for ouabain. These conformations transiently occur during a pumping cycle and their concentration may therefore be dependent on the frequency of cycling which in turn is determined by the frequency of contraction. 6 Ouabain can easily be washed out from the tissue irrespective of the condition of the muscle. If, however, the intracellular Na and K homeostasis is impaired, the inhibition of the pump persists even if ouabain is released from the binding sites upon wash‐out. It is suggested that the inhibition of the pump is maintained by an increased intracellular Ca ion concentration and a depletion of ATP. 7 A kinetic model is proposed for the interaction between cardiac glycosides and the Na‐K‐ATPase in intact heart muscle cells.

Inhibition of the actions of carbachol and DFP on guinea pig isolated atria by alkane-bis-ammonium compounds

Abstract In isolated guinea pig atria a number of newly synthesized alkane-bis-ammonium compounds abolish the intoxication induced by diisopropylfluorophosphate. This effect can be related to the antagonistic action of the compounds against acetylcholine and carbachol, respectively. The most powerful agents display pA10-values between 7.0 and 6.0 against carbachol. The mode of action of the alkane-bis-ammonium compounds differs from that of atropine and related substances. The compounds are not competitive antagonists, although they provoke a parallel shift of the dose response curves of carbachol to the right. The hypothesis is put forward that the alkane-bis-ammonium compounds react with side receptors thereby diminishing the accessibility of the acetylcholine receptor for the agonists (“allosteric antagonism”).

Accumulation of drugs by resting or beating cardiac tissue

The rate and degree of accumulation of 12 neutral, anionic and cationic drugs were studied in resting and 2 Hz-stimulated isolated left auricles of the guinea pig. The uptake process was accelerated in muscles driven electrically. The time needed to reach equilibrium was related to the extent of accumulation which in turn corresponded with the lipophilicity of the drug. The frequency-induced changes in the kinetics of the accumulation disappeared under reduced mechanical activity of the muscle. It is suggested that the increased mechanical activity enhances drug disposition within the extracellular space, so that more drug is available for transmembrane penetration.

An interaction of aminoglycoside antibiotics with Ca binding to lipid monolayers and to biomembranes

Thirteen aminoglycoside antibiotics were investigated with respect to their ability to replace Ca from phosphatidylserine monolayers. The affinities of the glycosides for the Ca-binding sites depended on the pH and the Ca2+ concentration of the aqueous subphase. At a Ca2+ concentration of 1.2 X 10(-5)M and a pH of 7.5 the half maximum concentrations to replace Ca were found to range from 0.4 X 10(-6) (sisomicin) to 6 X 10(-6)M (streptomycin). The interaction between the streptomycins and Ca were of a competitive nature, whereas the aminoglycoside antibiotics with higher affinities displayed unusual steep dose-response curves suggesting positive cooperativity. The aminoglycoside antibiotics were also able to replace Ca from biomembranes (red cell ghosts and isolated sarcolemma of cardiac muscle) in a dose-dependent manner. The high affinity of aminoglycoside antibiotics to a phospholipid is considered to be involved in the toxic side effects of these antibiotics, e.g. nephrotoxicity and impairment of contractile force.

PLASMALEMMAL CALCIUM IN CARDIAC EXCITATION-CONTRACTION COUPLING

1. Mammalian heart muscle is extremely sensitive to the external calcium concentration. It reacts to alterations of the external calcium concentration with an immediate adaptation of contractile force.

A comparative ultrastructural study of the effects of chlorphentermine and triparanol in rat lung and adrenal gland

SummaryChlorphentermine, an anorectic drug, and triparanol, an inhibitor of cholesterol biosynthesis, induce cytological alterations of essentially identical ultrastructural patterns, in pulmonary tissue and in adrenal cortex and medulla of the rat. In lung tissue, the predominant features are 1) the occurrence of numerous concentric lamellar inclusion bodies in alveolar macrophages, the number and size of which become increased, 2) the occurrence of lamellar inclusions as well as 3) unit-membrane-limited, dense cytoplasmic bodies, having a reticular or a crystalloid structure, in nearly all sessile cell types of pulmonary tissue. Pleomorphic inclusion bodies of the same kind occur in increased numbers within the cells of adrenal cortex and medulla. Irrespectively of the drug and of the type of cell, most lamellar bodies display a periodicity of approximately 45 Å, suggesting phospholipids or other lipids to be the major constituents of the inclusions. The observed cytological modifications are believed to reflect an abnormal intracellular accumulation of lipids.The triparanol-induced alterations are thought not to be related merely to inhibition of cholesterol biosynthesis, as has been suggested. On the contrary, a physicochemical feature, common to the molecules both of triparanol and of chlorphentermine, is believed to be responsible for the identical cytological effects of the drugs: due to the amphiphilic character of both compounds, an interaction with certain lipids is suggested to occur, which may interfere with the metabolic degradation, thus leading to an intracellular deposition of lipids. In conclusion, the described ultrastructural changes represent a lipidosis, induced by compounds of amphiphilic character.

The pharmacokinetics of phentermine and chlorphentermine in chronically treated rats

Young rats were treated with [3H]labelled phentermine or chlorphentermine for varying periods (1 day to 8 weeks). The plasma tissue and concentrations of the drugs were determined. The distribution of phentermine reflected a partition, the tissue: blood ratios remaining constant for the entire period. In contrast, chlorphentermine was increasingly accumulated the longer the treatment lasted, as indicated by rising tissue: blood ratios. Chlorphentermine proved to be tightly bound to tissue components. The highest tissue: blood ratio (160 after 8 weeks) was found in lungs and the highest increase in the accumulation rate (10 fold in 8 weeks) was for the adrenals. These results, together with biochemical and ultra‐structural findings, suggest that the highly amphiphilic chlorphentermine induces an impairment of phospholipid metabolism resembling lipidosis.

The significance of a fast exchanging superficial calcium fraction for the regulation of contractile force in heart muscle

Abstract The force of contraction of isolated guinea-pig atria decreased with time during 5 h of incubation in Tyrode solution containing 0.9 m m -CaCl2. The relative effect of ouabain strongly depended on the duration of incubation (“age”) of the tissue. Freshly dissected atria showed a 12% increase in contractile force, whereas aged atria (5 h of incubation) produced a 240% increase in tension in the presence of ouabain (1.5 × 10−7 m ). In freshly dissected atrial preparations, after an equilibration period of 30 mins, ouabain had no influence on Ca metabolism (total tissue Ca, rate of exchange, and size of exchangeable fraction). After aging of the tissue the rate of Ca exchange was significantly decreased, and ouabain considerably accelerated the Ca exchange rate. The presence of pentobarbital also slowed the Ca exchange rate. Ouabain was able completely to restore the rate of Ca exchange to control valves. Analysis of the Ca exchange curves yielded a fast and a slowly exchanging Ca compartment. The size of the fast exchanging fraction was significantly reduced by aging and by the treatment with pentobarbital. Under these conditions ouabain enhanced the size of this particular Ca compartment. It is suggested that the fast exchanging Ca compartment is superficially located and is responsible for rapid changes in contractile force. This Ca fraction may provide a Ca concentration of about 1.5 × 10−5 m in the intracellular aqueous space, which is generally believed to be sufficient for the activation of contraction.