title: Reduced external calcium or sodium stimulates calcium influx in Pelvetia eggs.
abstract: The effect of external calcium and sodium ion concentrations on the calcium fluxes on the Pelvetia fastigiata De Toni egg was measured. Decreasing external [Ca(2+)] greatly increased the permeability of the eggs to Ca(2+); at 1 mM external Ca(2+) this permeability was 60 times as great as it was at the normal [Ca(2+)] of 10 mM. Lowering the external [Na(+)] also increased Ca(2+) influx; at 2 mM Na(+), the Ca(2+) influx was 2-3 times as great as it was at the normal [Na(+)] if choline was used as a Na(+) substitute. Lithium was less effective as a Na(+) substitute in increasing Ca(2+) influx. The extra Ca(2+) influx in low [Na(+)] seemed to be dependent on internal [Na(+)]. The Ca(2+) efflux increased transiently and then declined in low Na(+) media.
authors.affiliation: Department of Biological Sciences, Purdue University, 47907, West Lafayette, IN, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Robinson