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

The divalent cations Ca2+, Mg2+, Co2+, Mn2+, Sr2+, and Ba2+ were compared for their stimulatory or inhibitory effect on PG formation in rabbit kidney medulla slices. Calcium, manganese, and strontium ions stimulated PG generation up to 3- to 5-fold in a time- and dose-dependent manner (Ca2+ greater than Mn2+ approximately Sr2+) while the magnesium and cobalt ions were without significant effects. Stimulatory effects of Ca2+, Mn2+, and Sr2+ on the medullary generation of PGE2 was found to correlate with their stimulatory effects on the release of AA and LL acids from tissue lipids. The release of other fatty acids was unaffected. As both AA and LL acids are predominantly found in the 2-position of phospholipids, the stimulation by these cations appears to be mediated via stimulation of phospholipase A2 activity.