title: Calcium transport in the cellular slime mould Dictyostelium discoideum.
abstract: Transport of Ca2+ into amoebae of Dictyostelium discoideum was studied using 45Ca and a lanthanum stopping technique. Ca2 uptake was found to be rapid and showed saturation kinetics. No difference was found in Ca2+ uptake between vegetative and aggregation competent cells, the V(max) for unstimulated amoebae being approx. 10 nmol/10(7) cells per min. Ca2+ uptake had the characteristics of passive facilitated diffusion using a saturatable carrier and NaN3 and ouabain were not inhibitory. The chemoattractants cAMP and folate, previously reported to stimulate the uptake of Ca2+ into amoebae, did not stimulate the rate of Ca2+ uptake by this carrier but increased the extent of Ca2+ taken up over the period 10-30 s after chemotactic stimulation. The significance of these findings for the function of Ca2+ in chemotactic signalling is discussed.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England.
authors.forename: G N
authors.initials: GN
authors.lastname: Europe-Finner
authors.forename: P C
authors.initials: PC
authors.lastname: Newell