COMPARISON OF THE RATE OF PHAGOCYTOSIS OF ORTHORHOMBIC CYCLOSPORINE-A(CSA) AND LATEX-PARTICLES BY ALVEOLAR MACROPHAGES FROM HAMSTERS

The aim of this study was to develop an in vitro model to estimate the clearance of pulmonary administered cyclosporine A (CsA). To do this we estimated the volume of CsA particles phagocytosed by alveolar macr ophages (AM) lavaged from hamsters. AM were cultured with CsA particle s at two doses of particles (0.1 mg or 0.5 mg) and at three incubation times (1 h, 6 h or 24 h). The AM were also incubated with or without latex particles. After incubation, AM were processed for light and ele ctron microscopy and the mean volume of phagocytosed particles was est imated stereologically from micrographs of the cells. Here, however, t he CsA particles were dissolved during the embedding process and only their negative images (vacuoles) could be detected. An indirect method was therefore developed. The volume of cytoplasmic vacuoles (called ' background' vacuoles) was estimated in control macrophages (without pa rticles or with latex particles and subtracted from the total volume o f vacuoles in macrophages incubated with CsA, which gave the volume of phagocytosed CsA. The volume of the 'background' vacuoles remained co nstant in all study conditions. Al a dose of 0.1 mg CsA the volume pha gocytosed per macrophage was 13.83 mu m(3) at 1 h, 8.43 mu m(3) at 6 h and 4.50 mu m(3) at 24 h. At a dose of 0.5 mg CsA, the volume phagocy tosed varied from 26.59 mu m(3) at 1 h, to 4.13 mu m(3) at 6 h and 49. 10 mu m(3) at 24 h. These results show no statistically significant de pendence on time for either dose, and a statistically significant dose effect only at 24 h. With latex particles, the phagocytosed volume in creased significantly with time and dose and was significantly higher than for CsA particles. This study showed that CsA particles are phago cytosed by AM from hamsters but to a lesser extent than latex particle s. This difference could be correlated with physical properties, i.e. a difference between particle size and shape and/or chemical propertie s, latex particles being inert and CsA particles being peptidic. Moreo ver, different surface receptors on AM could be involved in the proces s of phagocytosis of CsA and latex particles.