[Macro-creatine kinase: not all increased CK-MB activity signifies a heart infarct]

Assay of creatine kinase MB isoenzyme plays an important role in the diagnosis of acute myocardial infarction. An increase in CK-MB is frequently interpreted by the clinician as objective evidence of myocardial cell damage. However, increases of CK-MB may be found in several circumstances in which patients have not sustained an acute myocardial infarction. An important cause of elevated CK-MB values unrelated to acute MI is the presence of macro-creatine kinases in the patient's plasma. With immuno-inhibition procedures macro-CK is often measured as CK-MB, leading to falsely elevated CK-MB. In this paper macro-CKs, their clinical importance and their interference with CK-MB determination are discussed.

Mechanisms of cellular invasiveness: a comparison of amnion invasion in vitro and metastatic behavior in vivo

We employed a sensitive in vitro amnion invasion assay to examine the relationship of the invasive ability of numerous mouse and human tumor cell lines and their variants to their ability to spontaneously or artificially metastasize; we also studied possible enzymatic activities involved in the in vitro invasion process. In vitro invasive ability of tumor cells was strongly correlated with spontaneous metastatic ability from the subcutaneous site, regardless of the ability of tumor cells to form artificial metastases when introduced intravenously. However, normal nontumorigenic human trophoblast cells were also highly invasive. Various collagenase inhibitors totally abrogated amnion penetration by all invasive cells; various inhibitors of plasmin, plasminogen, and plasminogen activators prevented invasion in most, but not all, cases. Thus, amnion penetration provides a rigorous test for tumor cell invasiveness required for spontaneous metastasis in vivo, and invasiveness is strongly dependent on metalloproteinase activity, which usually follows plasmin activation.

Gelatinases of murine metastatic tumor cells

The properties of gelatinases secreted in culture medium of murine fibroblasts, macrophages, colonic carcinoma, FBJ virus-induced osteosarcoma, Lewis lung carcinoma and mammary tumor cells were compared. Normal fibroblasts and macrophages secreted gelatinases of 60,000 and 95,000 molecular weights, respectively. Tumor cells secreted both of these gelatinases, although the relative amounts of the 60 kDa and 95 kDa gelatinases differed among the cell lines. The cell lines that had the greatest metastatic potential to the lung secreted the highest amount of 95 kDa gelatinase. The 95 kDa gelatinase produced by tumor cells had properties similar to that of macrophages.

Activity of porphobilinogen deaminase in peripheral blood mononuclear cells of patients with metastatic cancer

Porphobilinogen deaminase (PBGD), one of the enzymes in the pathway of heme synthesis, was found to be elevated in peripheral mononuclear cells of 60% of patients with epithelial tumors and metastatic spread, but only in 14% of patients with tumor and no evidence of metastases. The combination of both high lactic dehydrogenase and high PBGD afforded a sensitivity of 40%, but a specificity of 96% in diagnosing metastatic spread.

Involvement of heparanase in tumor metastasis and angiogenesis

The capacity of various blood-borne cells, whether normal or malignant, to extravasate was found to correlate with heparanase-mediated degradation of HS in subendothelial ECM. This degradation was stimulated by proteases or plasminogen and inhibited by native heparin and by various modified nonanticoagulant species of heparin. These heparins also induced a marked reduction in tumor cell metastasis and autoimmune diseases in experimental animals. Heparanase-mediated degradation of HS in ECM also released EC growth factors that are stored in ECM, most likely by high affinity binding to HS. Such growth factors were extracted from subendothelial ECM synthesized in vitro and from basement membranes of the cornea in vivo, and are structurally and functionally related to bFGF;bFGF binds to ECM and is readily released by incubation with either HS, heparin or low MW heparin fragments as well as by various normal and malignant cells and by heparanase-mediated degradation of ECM HS. In contrast, there was little or no release of growth-promoting activity upon incubation of ECM with hyaluronic acid, chondroitin sulfate or chondroitinase ABC. A model is proposed suggesting that regulation of capillary growth and neovascular response may result from displacement of an angiogenic protein (bFGF) from its storage sites within basement membranes.

Ornithine decarboxylase activity in hepatic and extrahepatic metastases from colorectal cancer

The values of ornithine decarboxylase (ODC) activity in hepatic and extrahepatic metastases from primary colorectal cancer were studied. Adjacent noninvolved tissue was used as a control. Liver metastases had significant elevated ODC levels over surrounding liver (0.271 vs. 0.065, respectively, P less than .008). Results similar to those found in liver metastases were noted in extrahepatic metastases (median value, 0.271). This study discusses the possible reasons for these elevations and emphasizes that these differences may have potential roles in the areas of diagnosis, staging, monitoring of the disease, and therapeutic interventions in colorectal cancer and its hepatic and extrahepatic metastases.

Heparanases and tumor metastasis

The successful penetration of endothelial basement membranes is an important process in the formation of hematogenous tumor metastases. Heparan sulfate (HS) proteoglycan is a major constituent of endothelial basement membranes, and we have found that HS-degradative activities of metastatic B16 melanoma sublines correlate with their lung-colonizing potentials. The melanoma HS-degrading enzyme is a unique endo-beta-D-glucuronidase (heparanase) that cleaves HS at specific intrachain sites and is detectable in a variety of cultured human malignant melanomas. The treatment of B16 melanoma cells with heparanase inhibitors that have few other biological activities, such as N-acetylated N-desulfated heparin, results in significant reductions in the numbers of experimental lung metastases in syngeneic mice, indicating that heparanase plays an important role in melanoma metastasis. HS-degrading endoglycosidases are not tumor-specific and have been found in several normal tissues and cells. There are at least three types of endo-beta-D-glucuronidases based on their substrate specificities. Melanoma heparanase, an Mr approximately 96,000 enzyme with specificity for beta-D-glucuronosyl-N-acetylglucosaminyl linkages in HS, is different from platelet and mastocytoma endoglucuronidases. Elevated levels of heparanase have been detected in sera from metastatic tumor-bearing animals and malignant melanoma patients, and a correlation exists between serum heparanase activity and extent of metastases. The results suggest that heparanase is potentially a useful marker for tumor metastasis.

Evidence that sulphated polysaccharides inhibit tumour metastasis by blocking tumour-cell-derived heparanases

Recent studies in this laboratory demonstrated that several sulphated polysaccharides can inhibit metastasis of the rat mammary adenocarcinoma 13762 MAT, probably by preventing the passage of tumour cells through the walls of blood vessels. In order to directly test this possibility, 13762 MAT cells were cultured with (35S)O4(=)-labelled subendothelial extracellular matrices (ECM) and ECM degradation was monitored in either the presence or absence of different sulphated polysaccharides. Degradation products were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis and subsequent autoradiography. The 5 sulphated polysaccharides that had previously been shown to possess anti-metastatic activity were potent inhibitors of the degradation of subendothelial ECM by 13762 MAT cells. In contrast, of the 4 polysaccharides tested that failed to inhibit metastasis, 3 had no effect on ECM breakdown and one (carrageenan-kappa) was substantially less effective at inhibiting ECM degradation than the anti-metastatic preparations. It was also shown that 13762 MAT cells produce a heparan sulphate-specific glycosidase (heparanase) that degrades the heparan sulphate side-chains of the ECM, the action of this enzyme rather than that of other ECM-solubilizing enzymes being inhibited by the antimetastatic sulphated polysaccharides. Additional experiments indicated that the anti-coagulant activity of the polysaccharides probably plays a minor role in their anti-metastatic effects since heparin, almost completely depleted (98-99.5%) of heparin molecules with anti-coagulant activity by passage over an anti-thrombin III column, retained its ability to inhibit 13762 MAT heparanases and was almost as effective as unfractionated heparin at inhibiting tumour-cell metastasis. Collectively, these data suggest that sulphated polysaccharides inhibit the metastasis of 13762 MAT cells by inhibiting tumour-cell-derived heparanases involved in the penetration of the vascular endothelium and its underlying basement membrane by tumour cells.

Do proteases play a role in cancer invasion and metastasis?

The main difference between a benign and malignant tumor is the ability of the malignant form to invade normal tissue and spread or metastasize to distant sites throughout the body. It is the ability to form metastasis which makes cancer such a difficult disease to treat. Evidence suggesting that proteolytic enzymes are involved in cancer spread is as follows: proteases are involved in normal destructive events and tissue remodelling, correlations exist between different protease activities and metastatic potential in model tumor systems, inhibitors and antibodies against proteases inhibit metastasis in model systems and the finding of highest levels of protease activity at the invading front in tumors. The most likely mechanism by which proteases could mediate metastasis is by catalyzing degradation of the extracellular matrix and basement membranes. It is concluded that if proteases could be proved to play a role in the spread of human cancers, inhibition of these enzymes could open up new therapeutic approaches for the control of malignancy.

Heterogeneity of isozyme expression in tumor cells does not correlate with metastatic potential

The major purpose of these studies was to determine whether the expression of isozymes by tumor cells was heterogeneous among tumor cell subpopulations within a neoplasm and whether expression of one or another isozyme correlated with metastatic potential of tumor cells. The expression levels of 40 isozymes were determined in 56 cell lines, many of them clonal, from nine different murine and human tumors. The enzymes chosen for study are involved in nucleotide, carbohydrate and pentose phosphate metabolism, and as such are indicators of the general metabolic and differentiational status of the cell. The tumors studied included two murine and two human malignant melanomas, four murine fibrosarcomas, and one human prostatic adenocarcinoma. The lines isolated from these tumors consisted of cells that are tumorigenic non-metastatic, tumorigenic low metastatic and tumorigenic highly metastatic. Clonally derived cell lines from a given tumor differed in their expression of a number of different isozymes, including adenosine deaminase, creatine phosphokinase-B and lactate dehydrogenase. Different patterns of isozyme expression were observed among different tumor types as well as between tumors of the same type; however, there were no differences in isozyme expression for any enzyme tested that correlated with metastatic ability of tumor cells.

Characterization of an extracellular matrix-degrading protease derived from a highly metastatic tumor cell line

A proteolytic activity associated with the microsomal fraction of L-5178Y/Esb tumor cells has been characterized. The enzyme has a molecular weight of 80-90 kD as determined by affinity-labelling with [3H]DFP and SDS-gel electrophoresis. It cleaves ester substrates at the carboxyl position of lysine and arginine and can activate the proenzyme plasminogen. The enzyme is found to be associated with the plasma membranes of high and low metastatic tumor cell lines and is shed in high-molecular-weight form mainly by the high metastatic variant. The pH optimum for esterase and protease activities was 7.5-8.5. Although similar to trypsin in substrate specificity, the enzyme was not inhibited by lima-bean trypsin inhibitor but was inhibited by DFP, PMSF, aprotinin and leupeptin. Partially purified preparations of the protease can alone degrade 125I-labelled endothelial cell extracellular matrix, pointing at the putative role of this enzyme in tumor invasion.

Cathepsin B-like proteinase as a marker for metastatic tumor cell variants

Serial transplantation of a spontaneous BDX rat tumor, classified as an anaplastic sarcoma, gives rise to two variants; a rapidly growing nonmetastatic line (AS) and a slowly growing, invasive, and highly metastatic variant (ASML). The availability of two cell lines of the same origin but with markedly differing metastatic potential offers an ideal model for the identification of the cellular properties involved in invasive and/or metastatic behavior. The present work focuses on the pattern of various proteinases in the two tumor cell variants. The findings disclosed one major consistent difference which relates to a cathepsin B-like cysteine proteinase. The metastatic ASML variant manifests exceedingly high intracellular cathepsin B-like activity; in the nonmetastatic AS variant, the activity of this proteinase is significantly lower. Other proteinases, in particular elastase-like, chymotrypsin-like, collagenase-like enzymes and plasminogen activator, showed low, essentially comparable activity patterns. Thus, cathepsin B-like proteinase is a marker enzyme of the metastatic ASML tumor cell variant.

Ectopic creatine kinase MB production in metastatic cancer

This case concerns the presence of high serum levels of creatine kinase MB isoenzyme in a patient with metastatic cancer. This patient did not have a myocardial infarction, so the source of the CK-MB was investigated. Because of the observation of macro-creatine kinase in patients with cancer, it was necessary to rule out the presence of this form of the enzyme. Extensive laboratory analysis demonstrated that the isoenzyme was true CK-MB, not an atypical or macro CK. Results of the study showed that ectopic production of the isoenzyme was the apparent source of the high serum activity. Homogenization of the cancer tissue demonstrated the presence of a high percentage of CK-MB activity. The implications of CK-MB production in cancer are discussed, including the use of various technics to rule out interfering activities when situations such as this occur.

Secretion of basement membrane collagen degrading enzyme and plasminogen activator by transformed cells--role in metastasis

The relationship of a basement membrane collagen degrading enzyme (BM collagenase) and plasminogen activator (PA) was studied in a number of non-malignant and malignant human and murine cell lines. Several non-malignant cell lines secreted significant amounts of PA but not detectable BM collagenase activity whereas the malignant cell lines, with one exception, secreted both enzymes. Therefore, the secretion of BM collagenase appears to be a characteristic of many malignant cells whereas PA is synthesized also by normal cells. The BM collagenase needed proteolytic activation for maximal activity indicating that it is secreted in a latent form. The addition of plasminogen to the culture medium of human fibrosarcoma cells (HT-1080) resulted in maximal activation of the enzyme. Plasmin, but not plasminogen, increased the activity of partially purified enzyme protein. Accordingly, the activation of latent BM collagenase in vivo may be facilitated by PA through the conversion of plasminogen to plasmin. It is suggested that the secretion of BM collagenase concomitantly with PA is a prerequisite for metastasis.

Experimental model for quantitative study of metastasis

This paper describes the growth of HEp-3, a human epidermoid carcinoma, in the chick embryo. When inoculated onto the chorioallantoic membrane, the tumor grows locally with a doubling time of 21 to 24 hr and disseminates widely in the embryo proper, metastasis to the lung and heart being especially prominent. The tumor secretes large amounts of plasminogen activator (PA) both in vivo and in vitro. This enzyme of human origin can be easily identified in a mixture containing both human and chicken PA's, since each PA has a marked preference for the homologous plasminogen. Thus the presence of human PA in tissues and body fluids can be used as a quantitative marker for HEp-3 metastasis both in embryos and in newly hatched chicks. Two assays for metastasis are described; their respective sensitivities are less than 4 x 10(4) and less than 500 HEp-3 cells per 17-day chick embryo lung (or approximately 1 HEp-3 cell per 400 and per 3 x 10(4) lung cells), respectively. These assays revealed that tumor growth and metastasis are sensitive to embryo age, inoculation onto the chorioallantoic membrane at 10 days being optimal for both. Tumor size, the length of the latent period that precedes the appearance of lung metastasis, and the number of metastatic cells in the lungs are all influenced by inoculum size. Generally, but not uniformly, an increased level of lung metastasis is correlated with tumor size on the chorioallantoic membrane. The attractive features of this system for quantitative study of metastasis are reproducibility rapidity, sensitivity, convenience, and cost.

Serum tyrosinase in malignant disease, its activity, and the electrophoretic patterns of the enzyme as carried by immunoglobulins'

Serum tyrosinase activity in many persons with metastatic diseases was found to be significantly higher than activity in normal persons. The highest activity was observed in melanoma and breast carcinoma. The electrophoretic patterns of serum tyrosinase, resolved by electrophoresis of a serum tyrosinase fraction followed by incubation of the gel sample with L-dopa, and represented as sets of RF's of melanin bands, were characteristically different in melanoma, breast carcinoma, and certain other diseases. The RF's of melanin and protein bands in the serum enzyme preparations from melanoma patients were concisely defined. Further, some potent serum fractions inhibiting tyrosinase melanogenic activity have been obtained, and the presence of tyrosinase inhibitors in the serum enzyme preparation has also been demonstrated. More detailed exploration of these serum tyrosinase parameters may provide more specific and sensitive detection for certain malignant diseases.

Clinical application of immunodiffusion assay for prostatic acid phosphatase

The biochemical and immunologic characterization of acid phosphatase in serum and bone marrow was described as well as the clinical application of the immunodiffusion assay for prostatic acid phosphatase.

[The determination of phosphohexose isomerase in patients with cancer of breast and uterus. A comparison with other tests (author's transl)]

The levels of PHI are evaluated in 94 patients, who are classified by histological, scintigraphycal, radiological, biochemical and clinical test in: 16 patients, who suffer from some premalignant lesions of breast and uterus, 15 patients, who suffer from cancer of breast without metastases, 20 patients who suffer from cancer of breast with metastases, 18 patients who suffer from with cancer of uterus without metastases, 25 patients who suffer from cancer of uterus with metastases. The PHI activity is also evaluated in relation to the activity of other enzymes (LDH, AIP, G-GT). It has been revealed that: a) the PHI activity keeps within limits of normal value in patients who suffer from some pre-malignant lesions; b) all the patients suffer from cancer of breast without metastases show normal levels of PHI; c) in the patients with cancer of breast with metastases: 5 patients show normal levels of PHI, 5 patients show levels of PHI within limits, certainly 10 patients show pathological levels; d) in patients with cancer of uterus without metastases the value of enzymes results pathological in 6 patients, 6 patients show levels of PHI within limits that are above average and 6 patients show normal levels of PHI; e) the value of PHI always results high in patients with cancer of uterus with metastases.

Fucosyltransferase activity in metastasizing and nonmetastasizing rat mammary carcinomas

Fucosyltransferase levels in 6 established strains of spontaneously metastasizing rat mammary tumors (STMT-058, MT-449, DMBA-4, SMT-077, TMT-081, and SMT-2A) were compared with 4 nonmetastasizing strains (MT-W9B, MT-W9A, MT-100, and MT-66) as controls. Two acceptors were prepared from fetuin for the assay, one by acid hydrolysis of N-acetylneuraminic acid and the other by the stepwise removal of N-acetylneuraminic acid and penultimate galactose by Smith degradation. The enzyme that transfers fucose to the first acceptor was designated fucosyltransferase A, whereas the one that uses the second acceptor was designated fucosyltransferase B. Both types of fucosyltransferases were found in this rat mammary tumor system. Whereas the levels of fucosyltransferase A in the 2 tumor groups were comparable, those of fucosyltransferase B were sixfold to sevenfold higher in the metastasizing tumors. This difference in the level of fucosyltransferase B was not caused either by differential hydrolysis of GDP-fucose by pyrophosphatase in the 2 groups or by hydrolysis of the product by fucosidases. Presence of any other inhibitor(s) or activator(s) of fucosyltransferase was excluded by mixing experiments. Optimal conditions for the assay of this enzyme were determined in a representative strain from each group. Under all circumstances, the activity of fucosyltransferase B was higher in the metastasizing tumors. The enzyme was inhibited by nucleoside diphosphates and triphosphates, and guanosine nucleotides were the most efficient inhibitors. Subcellular distributions of the two fucosyltransferases were similar, 35-50% of the enzyme activity being present in the crude microsomes. When plasma membrane factions were prepared from the microsomes, the major part (50-70%) of the enzyme was associated with the light and heavy plasma membrane fractions. Increased activity of fucosyltransferase B in the group of metastasizing tumors may have reflected faster synthesis and shedding of fucose-containing glycoprotein antigens. Similar molecules possibly were also synthesized in the nonmetastasizing cells but at a much slower rate, because the antigen is not easily lost from the cell surface. Any alteration of the specificity of this focosyltransferase in the metastasizing tumors, in addition, may have caused antigen modulation.

Bone marrow acid phosphatase by radioimmunoassay

A double-antibody radioimmunoassay was developed and utilized to measure prostatic acid phosphatase in bone marrow aspirates. One hundred-eighteen patients with carcinoma of the prostate in various clinical stages, and fifty with benign prostatic hyperplasia were studied. In patients with carcinoma, levels of prostatic acid phosphatase in bone marrow aspirates were found to correlate well with increasing clinical stage of the disease. Determination of bone marrow prostatic acid phosphatase by radioimmunoassay may be a valuable adjunct to clinicopathologic staging of prostatic carcinoma.

Demonstration of the prostatic origin of metastases: an immunohistochemical method for formalin-fixed embedded tissue

An indirect immunohistochemical technique is described for identification of the prostatic origin of metastases in formalin fixed, paraffin or paraplast embedded material. A rabbit antiserum against the prostate specific acid phosphatase isoenzyme was developed. The method is applicable with or without previous decalcification. In 30 cases of prostatic carcinoma there was only one negative result, and in 20 cases of metastases from prostatic carcinoma positive results were obtained in every instance. All carcinomas (primary focus or metastasis) of non prostatic origin (55) stained negatively with the developed antiserum. The application and possible limitations of the method are discussed.

[Clinical significance of the determination of serum phosphohexose isomerase in malignant neoplasms]

The results of a preliminary study on the serous level of PHI in patients undergoing treatment at the Catania Oncology Institute are reported. Of 53 subjects with ongoing cancer, higher than normal values were encountered in 70% of cases. This percentage rose to 82.3% in cancer patients with metastasis affecting the skeleton. Of 12 subjects who underwent mastectomy with no clinical signs of recurrence only three showed abnormal values while in no case of fibrocystic mastopathy were levels higher than normal observed. A constant correlation was identified between effectiveness of surgical, radiotherapeutical or medical treatment and reduction in serous level of PHI. The usefulness of this investigation in oncology is thus confirmed.

Alterations in serum glycosyltransferases and 5'-nucleotidase in breast cancer patients

We have measured sialyltransferase, galactosyltransferase, and fucosyltransferase as sell as 5'-nucleotidase in the serum of breast cancer patients. Serum sialyltransferase values in 65 normal healthy females ranged from 2.6 to 8.5 units, with a mean of 5.4. In 25 women with operable primary breast cancer, serum sialyltransferase levels were found to be between 6.2 and 15.4 units. Marked elevation of this enzyme level (range, 8.8 to 36 units) was observed in 48 patients with metastatic breast cancer. Galactosyltransferase and fucosyltransferase measurements, however, showed considerable overlap between the controls and the cancer patients. On the other hand serum 5'-nucleotidase and sialyltransferase in breast cancer patients showed very similar patterns. Thus, serum 5'-nucleotidase values in 44 normal females ranged from 11.4 to 23.2 units, whereas the levels found in 30 patients with metastasis were between 25 and 71.8 units. The tissue origin of abnormal levels of serum glycosyltransferases and 5'-nucleotidase was discussed in relation to their physiological significance as well as their role as markers for diagnosing early malignant breast neoplasm and for monitoring the extent of metastasis.

Leukocyte alkaline phosphatase activity in patients with malignant disease

One hundred patients with malignant disease were screened for leukocyte alkaline phosphate (LAP) activity. The new observation made was that patients with malignant disease demonstrate significantly lower levels of LAP than in normal controls. The low LAP activity is present irrespective of primary tumor category, "activity" of disease, or type of therapy. The pattern of metastases may influence LAP activity, in that patients with liver metastases tended to have higher LAP levels. In spite of low baseline LAP levels in patients with malignant disease, the development of secondary infection is associated with elevated LAP levels.

Galactosyltransferase activity in metastasizing and nonmetastasizing rat mammary carcinomas and its possible relationship with tumor cell surface antigen shedding

In order to study the mechanism of tumor cell surface antigen shedding, galactosyltransferase levels were compared in 5 spontaneously metastasizing and 3 nonmetastasizing rat mammary tumors. The enzyme activity both with or without exogenous acceptors was higher in the metastasizing group. This difference did not seem to be due to the variation in levels of degrading enzymes such as pyrophosphatase or beta-galactosidase found in these tumors. Little difference in the biochemical properties of the enzyme was found between the two groups. Most of the enzyme activity (60-70%) was recivered in the microsomal frctosyltransferase was assayed in "purified" plasma membrane fractions, 70% of the activity was associated with the plasma membrane vesicles, in which the enzyme was enriched by factors of 10-40. The number of galactose acceptor sites on the plasma membranes increased in parallel to the metastasizing capacity, indicating the presence of larger numbers of incomplete glycopeptides on their cell surfaces. These findings seemed to indicate that the greater turnover of glycoprotein in the spontaneously metastasizing tumor cell surface was caused by the shedding of surface antigens into the systemic circulation of the host.

Low apparent creatine kinase activity and prolonged lag phases in serum of patients with metastatic disease: elimination by treatment of sera with sulfhydryl agents

We find lag phases exceeding 20 min in measuring creatine kinase activity, by using the kinetic creatin phosphate leads to creatine assay, in sera of some patients with carcinoma metastatic to the liver. Such long lag phases are accompanied by a decreased apparent enzyme activity. These problems are eliminated by adding sulfhydryl agents to the serum before assay, but not by adding more of such agents to the assay reagent. beta-Mercaptoethanol is supperior to Cleland's reagents, glutathione, and cysteine. The long lag phases could not be explained by inadequate activity of the coupling enzymes, interference with the coupling steps, high proportions of cardiacisoenzymes activity, simple oxidation of the enzyme, low concentrations of albumin, or increased concentrations of glutathione reductase, lactate dehydrogenase, or uric acid. We conclude that the prolonged lag phases reflect inadequate reactivation of the enzyme by sulfhydryl agents under the usual assay conditions. Reactivation before assay can prevent potentially serious negative errors in the assay of creatine kinase.

Biochemical properties of cyclic nucleotide phosphodiesterase in metastasizing and nonmetastasizing rat mammary carcinomas

The biochemical properties of cyclic nucleotide phosphodiesterases in a nonmetastasizing and a spontaneously metastasizing rat mammary carcinoma were compared. The phosphooiesterases in both tumors had a pH optimum of around 8.0 and preferentially hydrolysed cyclic purine nucleotides. The rate of hydrolysis of purine nucleotides in the nonmetastasizing tumor was two times higher than in the metastasizing tumor, but the rate of pyrimidine nucleotide hydrolysis was equal in both tumors. Theophylline, caffeine, and D,L-4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro20-1724) inhibited the enzyme activity in both tumors; the percent inhibition was the same by each inhibitor. The cyclic nucleotie phosphodiesterase activity in either tumor was stimulated by Mg++, Mn++, and Co++ and suppressed by Ca++, Zn,++, and Ni++. EDTA inhibited the activity below the basal level (activity in the absence of added cation), an this inhibition could be recovered up to the basal level by an equimolar quantity of either Mn++ or Mg++. Further stimulation of the enzyme activity with increasing concentrations of divalent cations was observed only with Mn++. Similar effects were observe with ethylene glycol bis(beta-aminoethyl ether)-tn,n-tetraacetic acid. The stimulatory cations affected both the low and high Michaelis constant (tkm) enzymes in these tumors by increasing the maximum velocity. In the low Km enzyme, the Km was also slightly increased. Neither guanosine 3',5'-cyclic monophosphate nor adenosine 3',5'-cyclic monophosphate had any effect on the hydrolysis of the other at physiologic levels.