title: Ca2+ signaling in the transformation of promastigotes to axenic amastigotes of Leishmania donovani.
abstract: The present study is an attempt to look into the role of Ca2+ in signaling the transformation of promastigotes to axenic amastigotes. An estimation of intracellular free calcium concentration at 6 h intervals during the conversion of promastigotes to axenic amastigotes (72 h) revealed a 10 fold increase in [Ca2+]i at the initial 6-12 h during the conversion. This was followed by declining levels till 60 h and the concentration thereafter remained constant. Axenic amastigotes (72 h) had a 5 fold higher [Ca+]i as compared to the promastigotes. A 30-40% decrease in [Ca2+]i after pretreatment of cells with dentrolene and a gradual rise of intracellular Ca2+ in [Ca2+] free medium indicates the role of intracellular calcium pools in the elevation of [Ca2+]i. A sudden increase in [Ca2+]i on addition of NH4Cl (20 mM) in the cells grown in Ca2+ free medium indicates the presence of acidocalcisomes, as intracellular Ca2+ storing pool, in L. donovani. To study the role of Ca2+ influx from the external medium in the morphogenetic transformation and in the elevation of [Ca2+]i a 45Ca2+ uptake study was performed. Maximum uptake of 45Ca2+ was observed in the initial 24 h of transformation and maximum Ca2+ ATPase activity was also observed between 24-42 h. So the presence of low Ca2+ in the cytosol, existence of intracellular Ca2+ pools and presence of mechanisms to maintain the Ca2+ homeostasis in the cells suggests that Ca2+ can be an appropriate candidate for a second messenger during the morphogenetic transformation of L. donovani.
authors.affiliation: Department of Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: A
authors.initials: A
authors.lastname: Prasad
authors.forename: S
authors.initials: S
authors.lastname: Kaur
authors.forename: N
authors.initials: N
authors.lastname: Malla
authors.forename: N K
authors.initials: NK
authors.lastname: Ganguly
authors.forename: R C
authors.initials: RC
authors.lastname: Mahajan
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology; D005434:Flow Cytometry; D005856:Germ-Free Life; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D007893:Leishmania donovani / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D009024:Morphogenesis / Q000187:drug effects; D013997:Time Factors
chemical_list: D000643:Ammonium Chloride; D000252:Calcium-Transporting ATPases; D003620:Dantrolene; D002118:Calcium