Immunocytochemical localization of the Ca2+-ATPase polypeptide in human platelets

Specific polyclonal antibodies raised against purified human platelet Ca2+-ATPase were used with protein A-gold immunocytochemistry to localize this protein in human platelets. Immunolabeling specifically detected Ca2+-ATPase over the surface connected membrane system (SCS) in sections of paraformaldehyde-fixed, Lowicryl-embedded platelets. The maximum density of label, determined by quantitative morphometric techniques, was observed over electron-dense regions within the SCS which may represent specialized structures for uptake and release of Ca2+. Less intense immunolabeling was observed over cytosol and may represent localization over the dense tubular system (DTS) which was not readily visualized under the processing procedures employed.     

Regulation of natural killer cell activity by macrophages in the rheumatoid joint and peripheral blood

Recently, in another study, we observed that indomethacin, a prostaglandin synthetase inhibitor, significantly increased NK activity in both normal and rheumatoid arthritis (RA) peripheral blood (PB) but not in RA synovial fluid (SF). Because macrophages are a major source of prostaglandins, we examined the effect of macrophage-enriched adherent cells (AC) on NK activity as measured by a 3-hr Cr-release assay with K 562 cells. The removal of AC resulted in increased (p less than 0.01) NK activity in both normal and RA PB. In contrast, the removal of AC from RA SF resulted in a significant decrease (p less than 0.001) of NK activity. By using only nonadherent cells (NAC), NK activity in RA SF and synovial tissue (ST) was significantly reduced when compared to autologous RA PB (p less than 0.001). Enhancement of NK activity of SF NAC by both poly I:C and IL 2 was not dependent on AC. Mixing experiments demonstrated that the addition of synovial AC for 16 hr increased NK activity of synovial NAC to a level similar to that of unseparated mononuclear cells, whereas autologous PB AC suppressed NK activity of PB NAC. PB AC, when added to SF NAC, also increased NK activity. Supernatants from synovial mononuclear cells were stimulatory of synovial NAC NK activity, whereas normal PB mononuclear supernatants were suppressive. These observations document 1) a significant reduction of NAC-mediated NK activity in the rheumatoid joint as compared to PB from the same patient, and 2) that AC modulate NK activity differently in the rheumatoid joint as compared to RA or normal PB.     

Eicosanoid-mediated increase in glucose and lactate output as well as decrease and redistribution of flow by complement-activated rat serum in perfused rat liver

Rat serum, in which the complement system had been activated by incubation with zymosan, increased the glucose and lactate output, and reduced and redistributed the flow in isolated perfused rat liver clearly more than the control serum. Heat inactivation of the rat serum prior to zymosan incubation abolished this difference. Metabolic and hemodynamic alterations caused by the activated serum were dose dependent. They were almost completely inhibited by the cyclooxygenase inhibitor indomethacin and by the thromboxane antagonist 4-[2-(4-chlorobenzesulfonamide)-ethyl]-benzene-acetic acid (BM 13505), but clearly less efficiently by the 5'-lipoxygenase inhibitor nordihydroguaiaretic acid and the leukotriene antagonist N-(3-[3-(4-acetyl-3-hydroxy-2-propyl-phenoxy)-propoxy]-4-chlorine-6-meth yl- phenyl)-1H-tetrazole-5-carboxamide sodium salt (CGP 35949 B). Control serum and to a much larger extent complement-activated serum, caused an overflow of thromboxane B2 and prostaglandin F2 alpha into the hepatic vein. It is concluded that the activated complement system of rat serum can influence liver metabolism and hemodynamics via release from nonparenchymal liver cells of thromboxane and prostaglandins, the latter of which can in turn act on the parenchymal cells.