15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and 5-hydroxy-6-8-11-14-eicosatetraenoic-acid

Renal glomerular injury frequently results in proliferation of a specialized supporting cell of the glomerular capillary known as the mesangial cell. In various forms of renal injury there is enhanced glomerular synthesis of specific eicosanoids of the arachidonic cyclooxygenase and lipoxygenase pathways including prostaglandin (PG) F2 alpha, thromboxane (Tx) A2, the hydroxyeicosatetraenoic acids 12-HETE and 5-HETE, and the leukotrienes LTB4 and LTD4 and attempts have been made to link these eicosanoids with injury-induced mesangial cell growth. In this study, the growth promoting effect of these eicosanoids on glomerular mesangial cells was correlated with activation of two growth regulatory enzymes: phospholipase C (PLC) and protein kinase C (PKC). PGF2 alpha, and TxA2 endoperoxide analog U-46619, and LTD4 significantly enhanced DNA synthesis [(as assessed by [3H]thymidine (TdR) incorporation)] in relatively quiescent (0.5% serum) mesangial cells, activated PLC [as assessed by increased 1,4,5-inositol tris-phosphate (IP3) generation and diacylglycerol (DAG) synthesis], and activated PKC (as assessed by translocation of the enzyme activity from the cytosol to the membrane). The effect of PGF2 alpha on IP3 generation was not blocked by the TxA2 receptor antagonist, SQ-29,548. PGF2 alpha was the most effective eicosanoid in inducing all three events, and concentrations that enhanced TdR incorporation (1 microM) also activated PLC and PKC. In contrast, concentrations of U-46619 and LTD4 which enhanced TdR incorporation (1 microM), also activated PLC, but were insufficient to also activate PKC. Our observations indicate that the growth-promoting effect of PGF2 alpha, U-46619, and LTD4 can best be correlated with PLC activation. In addition, PGF2 alpha does not mediate PLC activation through binding to the TxA2 receptor.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Cell Division; Diglycerides; Dinoprost; DNA; Eicosanoids; Enzyme Activation; Glomerular Mesangium; Hydroxyeicosatetraenoic Acids; Leukotriene B4; Leukotriene D4; Prostaglandin Endoperoxides, Synthetic; Protein Kinase C; Rats; Rats, Sprague-Dawley; Receptors, Thromboxane; Signal Transduction; Thromboxane A2; Type C Phospholipases

Anti-12(S)-hydroxyeicosatetraenoic acid (12-HETE)-antibody and anti-thromboxane B2 (TXB2)-antibody were generated and applied to the radioimmunoassay. The detection limit for 12-HETE was 16 pg. The cross-reactivities of anti-12-HETE-antibody were 4.6% for 15-HETE, 0.18% for 5-HETE and below 0.15% for leukotrienes and prostaglandins (PGs). 12-HETE and TXB2 released from guinea pig platelets were measured by radioimmunoassay. Platelet activating factor (PAF) at 10(-9) M induced the aggregation of platelets, the releases of immunoreactive-12-HETE (1.8 +/- 1.2 ng/10(8) platelets, mean +/- S.D.) and immunoreactive-TXB2 (18.5 +/- 17.3 ng/10(8) platelets). Collagen at 1 microgram/ml also evoked platelet aggregation, the releases of immunoreactive-12-HETE (2.7 +/- 1.1 ng/10(8) platelets) and immunoreactive-TXB2 (11.8 +/- 4.6 ng/10(8) platelets). By the stimulation with these compounds, TXB2 was produced in a greater amount than 12-HETE from guinea pig platelets. Although 10(-7) M and 10(-6) M U46619, a TXA2 mimetic, caused platelet aggregation, arachidonic acid metabolites were not released. These data suggest the presence of different mechanisms of platelet activation depending on each stimulus.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Antibodies; Blood Platelets; Chromatography, High Pressure Liquid; Collagen; Cross Reactions; Guinea Pigs; Hydroxyeicosatetraenoic Acids; Male; Platelet Activating Factor; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Radioimmunoassay; Thromboxane B2