Role of prostaglandins in the renal response to calcium infusion.

The effects of intrarenal infusions of calcium gluconate (10 and 100 micrograms Ca.kg-1.min-1) on renal hemodynamics and on renal excretory function were studied in anesthetized mongrel dogs. In one group, the two doses of calcium were infused for 30 min each (1 ml/min). In a second group, the same doses were administered 30 min after the start of an infusion of prostaglandin (PG) inhibitors (intrarenal indomethacin, 10 micrograms.kg-1.min-1, or intravenous bolus injection of meclofenamate, 5 mg/kg). No change with physiological significance was observed during the infusion of 10 micrograms Ca.kg-1.min-1. However, the infusion of 100 micrograms Ca.kg-1.min-1 induced increases (P less than 0.05) in glomerular filtration rate (50%), sodium excretion rate (180%), and fractional excretion of sodium (160%), with respect to control precalcium values. All these changes were prevented by the concurrent administration of PG synthesis inhibitors. Urinary PGE2 and 6-keto-PGF1 alpha increased 220 and 85%, respectively, during the infusion of 100 micrograms Ca.kg-1.min-1, but both decreased (P less than 0.05) below basal levels during the concurrent administration of PG synthesis inhibitors. The infusion of 100 micrograms Ca.kg-1.min-1 decreased (P less than 0.05) renal blood flow by 16% during the administration of PG synthesis inhibitors. These results suggest that PGs are mediating the increase in hemodynamic and excretory factors induced by the intrarenal infusion of 100 micrograms Ca.kg-1.min-1.