EFFECTS OF OSMOTIC-STRESS ON METABOLISM, SHAPE, AND AMINO-ACID CONTENT OF LEISHMANIA

An acute decrease in osmolality causes a rapid change in the shape of the parasitic protozoan Leishmania donovani as determined by light mic roscopy and by flow cytometry. Incubation of the cells in an isotonic buffer supplemented with glucose, 2-deoxyglucose (2-DG), alanine, or p roline also causes a shape change, presumably due to the swelling caus ed by the water that accompanies these substrates as they are actively transported into the cells. Hypo-osmolality also causes a rapid relea se of alanine and several other amino acids via a swelling activated a mino acid channel. A sudden increase in osmolality causes a change in shape, an inhibition in the rates of oxidation of alanine, proline, le ucine, and glucose, and in the rates of uptake of 2-aminoisobutyrate ( AIB) and 2-DG. The protein kinase inhibitors staurosporine and geniste in inhibited the rates of oxidation of alanine, glucose, and proline i n a culture-age dependent manner and also altered the rate of release of AIB in response to hypo-osmotic stress. The possible roles of prote in kinases in the culture-age dependent changes in the uptake, release , and metabolism of several amino acids and of glucose are discussed.