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Alkaline phosphatase isoenzymes in sera were resolved by electrophoresis on cellulose acetate membranes into seven different bands (L1, B, Pl, L2, l1, l2, and Pa, in decreasing order of electrophoretic mobility). The slowest moving band (Pa) was observed in the sera of 16 patients--15 with cancer of the pancreas and one with hemochromatosis. Sera of 50 other patients with malignant or benign diseases did not show the Pa band. The Pa band is more heat labile than is the liver isoenzyme (L1). Its behavior toward inhibitors (L-phenylalanine and L-homoarginine) is similar to that of L1. Sera containing the Pa band exhibit a diffuse band in the region where isoenzymes of intestinal origin migrate; however, its heat stability and sterospecific inhibition are different from those of intestinal isoenzymes in sera that show no Pa band.

Two forms of thrombin (Ts-thrombin and Tp-thrombin) were found with respect to heparin sensitivity. Inactivation of Ts-thrombin by antithrombin-III was facilitated with heparin, whereas inactivation of Tp-thrombin was not. Both thrombins were bound to heparin in a Sephadex G-200 gel filtration experiment. Ts-thrombin proved to be more stable and was better protected by heparin against heat inactivation of 54 degrees C than Tp-thrombin.

The mechanism of endocytosis in resealed human erythrocyte ghosts was studied. The energy for endocytosis or micropinocytosis appears to be derived from Mg-ATP, and membrane internalization is preceded by activation of a membrane-associated Ca,Mg-ATPase and by the active efflux of Ca. Endocytosis, Ca,Mg-ATPase activity, and active Ca efflux all require the presence of Mg. Furthermore, these three phenomena, endocytosis, Ca,Mg-ATPase activity, and active Ca extrusion, all have a concentration dependence on Ca such that low concentrations stimulate and higher concentrations inhibit the phenomena. The optimal concentration of Ca is identical for endocytosis, active Ca efflux, and Ca,Mg-ATPase. Morphologic studies indicated that while active Ca efflux and activation of the Ca,Mg-ATPase activity occurred promptly upon onset of incubation, there was a significant time delay before endocytosis occurred, which suggests that endocytosis additionally involved a more slowly functioning mechanicochemical mechanism. Ruthenium red, a specific inhibitor of Ca,Mg-ATPase and Ca transport, inhibited endocytosis in a concentration-related manner. Prostaglandins E1 and E2 had no measurable effect on ghost endocytosis, active Ca efflux, or Ca,Mg-ATPase activity.