Effects of bivalent cations on prostaglandin biosynthesis and phospholipase A2 activation in rabbit kidney medulla slices

Publisher Website
Google Scholar
Abstract
The bivalent cations Ca2+, Mg2+, Co2+, Mn2+, Sr2+ and Ba2+ were compared for their stimulatory or inhibitory effect on prostaglandin [PG] formation in rabbit kidney medulla slices. Ca2+, Mn2+ and Sr2+ ions stimulated PG generation up to 3 to 5 fold in a time- and dose-dependent manner (Ca2+ > Mn2+ .simeq. Sr2+). The stimulation by Mn2+ (but not by Sr2+) was also observed in incubations of medulla slices in the presence of Ca2+. Mg2+ and Co2+ ions were without significant effects on either basal or Ca2+ stimulated PG synthesis. The stimulatory effects of Ca2+, Mn2+ and Sr2+ on medullary generation of PGE2 correlated with their stimulatory effects on the release of arachidonic acid and linoleic acid from tissue lipids. The release of other fatty acids was unaffected, except for a small increase in oleic acid release. As both arachidonic acid and linoleic acid are predominantly found in the 2-position of the glycerol moiety of phospholipids, the stimulation by these cations of PGE2 formation appears to be mediated via stimulation of phospholipase A2 activity.