RESIDENT AND CIRCULATING MAST CELLS IN PROPULSATIVE ORGANS OF THE FROG RANA TEMPORARIA
M. I. Krylova
Institute of Cytology, RAS, St. Petersburg;
e-mail: heartdev@mail.cytspb.rssi.ru
Mast cells (MCs) of the "blood" and lymph hearts of the adult frog Rana temporaria were investigated at histochemical and ultrastructural levels. Two populations of MCs
were revealed in these propulsative organs: population of resident MCs and population of circulating MCs. It has been shown that the resident cardiac MCs have an oval or
elongated form and are located between atrial or ventricular myocytes and under endocardial endothelium. The resident cardiac MCs are situated in connective tissue of
epicardium, too. Avascular myocardium of the frog ventricle consists of a spongy network of muscle trabeculae. We revealed circulating MCs in intertrabecular spaces and
clefts of the spongy myocardium and in the blood of the main central cavity. Circulating MCs are round in shape and contain a large central nucleus enriched with condensed
chromatin. They resemble the lymphocytes, but show cytoplasm filled with granules. These granules ultrastructure is much like that of the granules of the cardiac resident
MCs. In the lymph heart, oval and somewhat elongated resident MCs are located in the interstitial space among cross-striated muscle fibers and among smooth muscle cells
of tubular (afferent and efferent) valves. Sometimes lymphocyte-like circulating MCs are revealed in the cavity of lymph heart. Circulating MCs are also present in the
lymphatics located adjacent to the lymph hearts. In certain parts of the lymphatic walls MCs are in close adhesion to the mesothelial cells lining the lymphatic cavity. Our
histochemical investigation revealed that both the resident and circulating MCs of the propulsative organs give a strongly positive reaction with alcian blue, but weakly red
with safranin and weakly metachromatic with toluidine blue. The presence of population of circulating MCs in the frog suggests that there are differences in biology of MCs
between lower and higher vertebrates.
Key words: mast cells, "blood" heart, lymph heart, histochemistry, electron microscopy, frog Rana temporaria
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