calcimycin and Hydronephrosis

The effect of the calcium channel blocker verapamil on prostaglandin (PG) E2 production by hydronephrotic cortical interstitial cells in primary culture was investigated. Verapamil displayed a dual action, maximally enhancing PGE2 production from 1.2 +/- 0.2 to 30.7 +/- 4.3 ng/ml at 30 microM, whereas at higher concentrations the effect tapered down to base line. Stimulation of PGE2 synthesis by verapamil required extracellular calcium, but was unaffected by the intracellular calcium inhibitor 8-(Diethylamino)octyl 3,4,5-trimethoxy-benzoate or the calmodulin inhibitor trifluoperazine. Other calcium channel blockers, nifedipine and diltiazem, failed to stimulate PGE2 synthesis, implying that this effect of verapamil was unrelated to its commonly recognized action to inhibit calcium channels. However, stimulation by verapamil was inhibited by quinacrine (mepacrine), suggesting a mechanism involving activation of a phospholipase. In addition, verapamil attenuated the bradykinin- or ionophore A23187-stimulated PGE2 production, but it did not alter arachidonic acid-induced PGE2 synthesis. These observations indicate that, in addition to phospholipase activation, verapamil may also act to inhibit phospholipase activity. Inhibition was concentration-dependent over the range 3 to 300 microM, and was reversible. It is concluded that verapamil, at different concentrations, exerts a dual action on cellular phospholipase activity, thereby stimulating, and in turn inhibiting, PGE2 synthesis by hydronephrotic interstitial cells.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Bradykinin; Calcimycin; Calcium; Cells, Cultured; Diltiazem; Dinoprostone; Dose-Response Relationship, Drug; Hydronephrosis; Kidney Cortex; Magnesium; Male; Nifedipine; Prostaglandins E; Quinacrine; Rabbits; Trifluoperazine; Verapamil

Rabbit hydronephrotic cortical interstitial cells in primary culture were labeled with [1-14C]arachidonic acid and the eicosanoids released after stimulation with bradykinin or A23187 were studied by reverse-phase high performance liquid chromatography. The major arachidonic acid metabolite formed was prostaglandin (PG)E2, comprising more than 30% of the total radioactivity released. 12-Hydroxyheptadecatrienoic acid, probably representing spontaneous breakdown of the cyclic endoperoxides PGG2 and/or PGH2, made up 10 to 15% of the radioactivity released. Other cyclooxygenase products that were released included PGF2 alpha, PGD2, 6-keto PGF1 alpha and only minute amounts of thromboxane B2. Small quantities of the lipoxygenase products 15-, 12- and 5-hydroxyeicosatetraenoic acids (HETEs) as well as leukotrienes (LT)B4, LTC4 and LTD4 were also identified. Significantly larger quantities of 15- and 5-HETEs were recovered at 2 to 5 min than after longer incubations with A23187, suggesting esterification of these HETEs into cellular phospholipids. The data indicate that interstitial cells of the hydronephrotic kidney synthesize a variety of cyclooxygenase and lipoxygenase products of arachidonic acid, which may contribute to the pathophysiology of hydronephrosis. Moreover, it is suggested that PGG2 and/or PGH2 that are released from these cells may be metabolized further by adjacent kidney cells or circulating blood elements to other eicosanoid products, thus increasing the diversity of eicosanoids synthesized in the hydronephrotic kidney.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Bradykinin; Calcimycin; Cells, Cultured; Chromatography, High Pressure Liquid; Dinoprostone; Eicosanoic Acids; Hydronephrosis; Hydroxyeicosatetraenoic Acids; Kidney Cortex; Leukotrienes; Male; Prostaglandins E; Prostaglandins G; Rabbits; SRS-A; Strontium