Uptake, accumulation, and egress of erythromycin by tissue culture cells of human origin

Abstract

The ability of erythromycin A base to penetrate and accumulate in tissue culture cells of human origin was investigated. The antibiotic was highly concentrated by early passage ceUls of normal bronchus, kidney, liver, lung, and skin and by cancer ceUs derived from breast, liver, and lung. Intracellular levels 4 to 12 times that of the extracellular milieu were obtained in both early-passage and transformed cells. The total quantity of erythromycin accumulated depended on the extracellular concentration of antibiotic, but the cellular/ extracellular ratios were, for the most part, independent of the initial extracellular drug concentration. In all cell types tested, the accumulated antibiotic rapidly egressed when cells were incubated in antibiotic-free medium. Bioactivity assays demonstrated that the expelled drug was unmetabolized, fully active antibiotic. The concentration of erythromycin by a variety of human cell types probably accounts, in part, for the effectiveness of the antibiotic against intracellular parasites such as Legionella and Chlamydia spp.Erythromycin has been widely, successfully, and safely used for over two decades as treatment for infections caused by susceptible pathogens. Although erythromycin has been recognized as an effective drug, investigators have been puzzled by the low and unpredictable levels in plasma that are usually observed after administration of the antibiotic. The paucity of drug in the vasa may be due to tissue accumulation, since distribution studies on tissue samples excised from dogs (14) and rats (15) have shown that erythromycin is concentrated well above blood levels in organs such as the liver, spleen, kidney, lung, and pancreas and in submaxillary and adrenal glands.Infections attributed to Legionella spp., which are facultative intracellular bacteria, and Chlamydia spp., which are obligate intracellular parasites, are effectively treated with erythromycin (1). Both organisms are known to parasitize a large number of human cell types. The ability of erythromycin to control these organisms suggests that the antibiotic penetrates and exerts its action within the invaded host cell. Indeed, recent studies have shown that both human polymorphonuclear leukocytes (PMNs) (20, 23) and alveolar macrophages (8,12) The resulting [3H]erythromycin was extracted with methylene chloride and crystallized from acetonitrile. Further purification by high-pressure liquid chromatography on a C18 column with a mobile phase consisting of acetonitrile (1,350 ml), methanol (300 ml), 0.2 M ammonium formate (300 ml), water (1,050 ml), and ammonium hydroxide (0.6 ml) (pH 7.5 to 8.0) gave [3H]erythromycin A base (specific activity, 19.5 mCi/mmol; >98% radio pure

Intracellular accumulation of azithromycin by cultured human fibroblasts

“…As previously observed with phagocytic cells, the intracellular accumulation of azithromycin exceeded that of erythromycin (up to 27 times) at all times examined. The degree of intracellular accumulation of erythromycin was higher than that previously reported by Martin et al (16), who utilized different incubation conditions (i.e., the use of suspended rather than adherent cells). Nevertheless, the differential uptake between azithromycin and erythromycin should remain the same and may be a reflection of the higher tissue levels of azithromycin reported (7,10,20).…”

“…Studies examining the effects of various inhibitors on uptake utilized a 1-h preincubation period prior to adding the radiolabeled antibiotic. By using these techniques, the intracellular accumulation of erythromycin was 2.5 times higher than that previously reported (16); however, in that study, uptake was determined for cells maintained in suspension rather than for adherent cells.…”

“…The uptake and release of azithromycin were compared with those of erythromycin, since erythromycin is readily available commercially and its uptake has been studied extensively in other cell types (4,11,13,16). The methods utilized for uptake in this study were essentially the same as those previously described (11).…”

Intracellular pharmacodynamics of antibiotics

“…In sharp contrast with b-lactams, macrolides show a marked intracellular accumulation in almost all cells [5,14,15,[22][23][24][25][26][27]. The extent of their accumulation, however, varies markedly among derivatives, with relatively low values for erythromycin and single-base macrolides, to extensive values for those macrolides carrying two basic functions.…”

Measurement of Cefaclor and Amoxicillin-Clavulanic Acid Levels in Middle-Ear Fluid in Patients with Acute Otitis Media

“…The CϪ fraction was obtained via a velocity gradient technique (8,9). Briefly, the samples were centrifuged at 14,000 ϫ g for 5 min in microtest tubes containing 200 l of a mixture of silicone oils (556-550, 5:6 vol/vol; Dow Corning), separating the cells from extracellular fluid.…”