Inhibition of protein cross-linking in Ca2+-enriched human erythrocytes and activated platelets.

Treatment of human erythrocytes with Ca2+, in the presence of ionophore A23187, causes the formation of high molecular weight (greater than 10(6)) membrane protein polymers. This phenomenon, known to involve cross-linking of essentially all of the band 4.1 and 2.1 (ankyrin) proteins, as well as some spectrin, band 3, and hemoglobin molecules, could be prevented by preincubating the cells with a noncompetitive inhibitor of intrinsic transglutaminase, 2-[3-(diallylamino)propionyl]benzothiophene, at concentrations of about (3-6) X 10(-4) M. The compound also eliminated the proteolytic breakdown of the two major transmembrane proteins band 3 and glycophorin, which would otherwise occur during the Ca2+ loading of fresh human red cells. In addition, the inhibitor effectively blocked the formation of a cross-linked protein polymer in thrombin-activated human platelets.

Characteristics of separated epithelial and stromal subfractions of prostate: II. Human prostate.

Surgical samples of human benign prostatic hyperplasia tissue (BPH) were fractionated into epithelial clumps and stromal fractions, using the "optimal" tissue dissociation procedure developed for rat prostate described in the preceding report. The separated cellular fractions were compared to control unfractionated tissue (wherein extracellular secretory products had been removed) with respect to the concentrations of androgen receptor and enzyme markers on a DNA basis; cell damage was also evaluated by light and electron microscopy (EM). EM revealed extensive cell damage in epithelial clumps and stromal fractions, which had appeared normal when examined by light microscopy. Damage to the ultrastructure of individual epithelial cells present in clump fractions was very variable, involving vacuolization of the cytoplasm and condensation of nuclear chromatin in some cells, vacuolization of just the cytoplasm in other cells; only a small fraction of the cells in clumps had normal ultrastructure. Ultrastructural damage to stromal cells was much greater in fibroblasts than in muscle fibers. The cell damage observed in both subfractions of human prostate was associated with a marked degree of receptor loss. The mean decreases in the number of androgen receptors per unit DNA relative to control unfractionated tissue was 68.5 and 62.5% recovered in epithelial and stromal fractions, respectively. Measurement of various enzymes as "markers" revealed that acid phosphatase activity (per unit DNA) was associated exclusively with the epithelial clump fraction. Prolyl hydroxylase and myosin ATPase activities (per unit DNA) were restricted to the stromal fraction. The limitations of using mechanically separated subfractions of human prostate tissue for evaluation of the cellular distribution or the initial concentration of steroid receptors in human prostate tissue are discussed.

Characteristics of separated epithelial and stromal subfractions of prostate: I. Rat ventral prostate.

These studies were initiated with the objective of isolating epithelial and stromal cells of human prostatic tissue in undamaged state, in order to study the cellular distribution of steroid receptors in benign prostatic hyperplasia (BPH) relative to normal prostate. Initial experiments showed that when BPH tissue immersed in tissue culture media was progressively fragmented by various cutting procedures, epithelial elements were selectively released as clumps of variable size and individual cells, but that a large percentage of these cells were damaged, as evidenced by their failure to exclude trypan blue (TB). These observations suggested that if tissue fragmentation were carried out under defined conditions that minimize cell damage, BPH subfractions might be obtained containing a large percentage of undamaged cells. To determine conditions of tissue fragmentation which result in maximal recovery of epithelial cells which exclude TB, rat ventral prostate (RVP) was chosen as a model system. Experiments with RVP revealed that maximal yields of such cells were obtained in "large" epithelial clumps (greater than 30 cells per clump) released under the following conditions: (1) chopping the tissue with razor blades in a large volume (2 ml/100 mg RVP) of a Ca2+-free tissue culture medium ( Joklik 's-MEM) containing 1% casein, (2) carrying out the entire fractionation procedure in the cold, and (3) maintaining a 1% casein concentration in the medium during chopping, as well as in subsequent washing procedures, to protect cells from proteolytic activity. In large epithelial clumps, cells in the interior of the clump were not stained by TB but the cells at the periphery of the clump were freely permeable to TB. Single epithelial cells and small epithelial clumps (3-10 cells) released by razor blade fragmentation were also permeable to TB. When large epithelial clumps were incubated at 20 degrees C for 90 min, the clumps disaggregated into smaller clumps and morphologically intact single cells, which did not exclude TB. The residual tissue fragments remaining after chopping contained the bulk of stromal cells plus some epithelial elements. The latter could be removed by gentle rubbing of the fragments on a sieve in the presence of medium. The stromal fraction thus obtained consisted of stromal cells, embedded in mesenchymal matrix, which were not stained by TB and appeared normal when examined histologically by light microscopy.(ABSTRACT TRUNCATED AT 400 WORDS)

Androgen and estrogen receptors in rat ventral prostate epithelium and stroma.

Estrogen and androgen receptors have been investigated in rat ventral prostate epithelium and stoma. High speed supernatants were prepared from unfractionated or fractionated prostates. Cytosols from intact rats were incubated with 2 nM 3H-estradiol (E2) in presence of 80 nM dihydrotestosterone (DHT), and cytosols from 1 day castrated rats were incubated with 2 nM 3H-DHT, at 0 C for 4 h. They were submitted to ultracentrifugation on glycerol-Tris gradients. The amounts of hormones bound to the saturable 8S binding components were determined on a comparative basis. The values for E2-receptor in intact rats were 2.3, 15.4 and 5.9 fmol/mg cytosol protein in unfractionated prostate, stroma and epithelium, respectively. The corresponding values for DHT-binding were 31.9, 17.2 and 29.2 fmol/mg protein. In addition, Scatchard analysis of saturable E2 and DHT binding, using the protamine precipitation technique, essentially confirmed the results of glycerol gradients, and led to the conclusion that, contrary to androgen receptor, the major part of estradiol receptor is localized in stroma.

Ca2+-dependent cross-linking processes in human platelets.

When platelet cytoplasmic Ca2+ is increased by the ionophore A23187 in the presence of the protease inhibitor leupeptin, there is the coincident appearance of a cross-linked polymer and the partial disappearance of monomeric protein and glycoprotein units. In the absence of leupeptin only 30% of the polymer was formed. The disappearance of monomeric protein bands, as detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, is prevented by histamine, which as a pseudodonor amine is a known inhibitor of transglutaminase-catalyzed cross-linking [14C]Histamine, at a tracer concentration, is incorporated into the polymer as well as into myosin, glycoproteins IIb and III, actin and tropomyosin. The loss of monomeric protein bands is mostly due to their conversion into polymers. Control measurements show that leupeptin effectively inhibited platelet Ca2+-dependent proteases. The cross-linking processes bringing about the observed increase in polymer formation are thus the result of a Ca2+-dependent platelet transglutaminase activity. The latter is located in the platelet cytosol and has been identified as platelet factor XIII on the basis of its specific cross-linking of fibrin. Platelet factor XIII, upon activation, may function physiologically to couple membrane proteins to cytoplasmic structural proteins. Thus, a new concept is proposed for the stabilization of platelet membranes and platelets as they form the hemostatic plug.

Role of the intrinsic transglutaminase in the Ca2+-mediated crosslinking of erythrocyte proteins.

Transamidase (i.e., "transglutaminase") activity of human erythrocytes, lysed by a single freezing and thawing to 37 degrees, was measured by a method of incorporating [14C]putrescine into N,N'-dimethylcasein. In the absence of added calcium ions, virtually no enzyme activity could be detected. An increase in concentration of the cation to about 0.5 mM, however, turned on the enzyme to appreciable levels of activity. Simultaneously, Ca2+ produced formation of high molecular weight, nondisulfied bonded protein polymers either directly in the lysate or in fresh cells when the cation was added together with the A23187 ionophore. The polymers could be readily identified in the isolated cell ghosts by means of disc gel electrophoresis. If the Ca2+-promoted formation of polymers was allowed to take place in the presence of 14C-putrescine, then this tracer became incorporated into the polymeric material. The incorporation indicated that polymerization occurred through gamma-glutamyl-epsilon-lysine bridtes. It is suggested that the intrinsic transamidase mediates protein crosslinking of the erythrocyte membrane whenever there is an increase in intracellular Ca2+ concentration. The presence of suitable transglutaminase substrates, e.g. histamine, inhibited crosslinking when the cells were incubated with Ca2+ and ionophore.

A pathological inhibitor of fibrin cross-linking.

Lewis et al. recently reported on a patient who died of hemorrhages attributable to an acquired inhibitor of fibrin-stabilizing factor. They indicated that the inhibitor was associated with the immune globulins. Using the postmortem serum in the isolated fibrin cross-linking system, we have now further localized the site of inhibition in the scheme of blood coagulation. The interference occurs at the transpeptidation step catalyzed by the thrombin-activated fibrin-stabilizing factor. The patient's serum also uniquely delayed the clotting time of Homarus plasma, a test for specific inhibitors of transpeptidation. Since the inhibitor was effective in two such widely different systems, it probably is not an antibody, but falls into the category of cross-linking inhibitors which we have previously described (4, 5, 10, 12-17). While the exact nature of the inhibitor remains unknown, we raise the question whether some unusual metabolic transformation of isonicotinic acid hydrazide (with which the patient was treated and which itself we found to be a potent inhibitor fibrin cross-linking), in combination with a macromolecule, might not have given rise to an inhibitory compound.