Inhibition of growth and guanylate cyclase activity of an undifferentiated prostate adenocarcinoma by an extract of the balsam pear (Momordica charantia abbreviata)

Bitter Melon (Momordica Charantia), a Nutraceutical Approach for Cancer Prevention and Therapy

Cancer is the second leading cause of death worldwide. Many dietary plant products show promising anticancer effects. Bitter melon or bitter gourd (Momordica charantia) is a nutrient-rich medicinal plant cultivated in tropical and subtropical regions of many countries. Traditionally, bitter melon is used as a folk medicine and contains many bioactive components including triterpenoids, triterpene glycoside, phenolic acids, flavonoids, lectins, sterols and proteins that show potential anticancer activity without significant side effects. The preventive and therapeutic effects of crude extract or isolated components are studied in cell line-based models and animal models of multiple types of cancer. In the present review, we summarize recent progress in testing the cancer preventive and therapeutic activity of bitter melon with a focus on underlying molecular mechanisms. The crude extract and its components prevent many types of cancers by enhancing reactive oxygen species generation; inhibiting cancer cell cycle, cell signaling, cancer stem cells, glucose and lipid metabolism, invasion, metastasis, hypoxia, and angiogenesis; inducing apoptosis and autophagy cell death, and enhancing the immune defense. Thus, bitter melon may serve as a promising cancer preventive and therapeutic agent.

Antioxidant, Antibacterial, and Anticancer Activities of Bitter Gourd Fruit Extracts at Three Different Cultivation Stages

In this study, we are presenting the effect of three ripening stages of air-dried bitter gourd fruit extracts on phenolic acid composition, antioxidant, antibacterial, and anticancer activities. The results showed mature bitter gourd fruit extract in 100% methanol showing 78% DPPHº scavenging activity. Immature dried fruit extract in 80% and 100% methanol showed promising antibacterial activities, i.e., >18.5 ± 0.21 mm zone-of-inhibition against Staphylococcus aureus, while mature dried fruit extract in 80% methanol showed 18.4 ± 0.17 mm zone-of-inhibition against Escherichia coli. Anticancer activity results of 100% methanol extracts of ripened fruit possess showed 6.72 ± 1.81 and 3.55 ± 0.51 mg/mL IC50 values with HeLa and MDBK cancer cell lines, respectively. The overall results indicate that the immature and ripen fruits of BG could be extracted in pure methanol as an antibacterial and anticancer phytomedicine.

Recent Advances in Momordica charantia: Functional Components and Biological Activities

Momordica charantia L. (M. charantia), a member of the Cucurbitaceae family, is widely distributed in tropical and subtropical regions of the world. It has been used in folk medicine for the treatment of diabetes mellitus, and its fruit has been used as a vegetable for thousands of years. Phytochemicals including proteins, polysaccharides, flavonoids, triterpenes, saponins, ascorbic acid and steroids have been found in this plant. Various biological activities of M. charantia have been reported, such as antihyperglycemic, antibacterial, antiviral, antitumor, immunomodulation, antioxidant, antidiabetic, anthelmintic, antimutagenic, antiulcer, antilipolytic, antifertility, hepatoprotective, anticancer and anti-inflammatory activities. However, both in vitro and in vivo studies have also demonstrated that M. charantia may also exert toxic or adverse effects under different conditions. This review addresses the chemical constituents of M. charantia and discusses their pharmacological activities as well as their adverse effects, aimed at providing a comprehensive overview of the phytochemistry and biological activities of M. charantia.

Momordica charantia: a popular health-promoting vegetable with multifunctionality

Products derived from edible medicinal plants have been used for centuries to prevent, treat, and even cure multiple diseases. Momordica charantia L., widely cultivated around the world, is a typical one bred for vegetables and medicinal usage. All parts of M. charantia possess important medicinal properties, including antidiabetic, anticancer, hypotensive, anti-obesity, antimicrobial, antihyperlipidemic, antioxidant, anti-inflammatory, immuno-modulatory, anthelmintic, neuro-protective, as well as hepato-protective properties both in vitro and in vivo. This review summarizes the active components and medicinal properties of M. charantia, especially the activities and mechanisms of its anti-diabetic and anti-cancer properties. The anti-diabetic properties involve inhibiting intestinal α-glucosidase and glucose transport, protecting islet β-cells, enhancing insulin secretion, increasing hepatic glucose disposal, decreasing gluconeogenesis, and even ameliorating insulin resistance. Moreover, the expressions of PPARs could also be activated and up-regulated. Meanwhile, its anticancer properties are mostly due to apoptosis, cell cycle arrest, and expression of serum factors associated with immunity. In this review, we aim to provide an overview of M. charantia and its benefits for development as a functional food.

Promise of bitter melon (Momordica charantia) bioactives in cancer prevention and therapy

Recently, there is a paradigm shift that the whole food-derived components are not 'idle bystanders' but actively participate in modulating aberrant metabolic and signaling pathways in both healthy and diseased individuals. One such whole food from Cucurbitaceae family is 'bitter melon' (Momordica charantia, also called bitter gourd, balsam apple, etc.), which has gained an enormous attention in recent years as an alternative medicine in developed countries. The increased focus on bitter melon consumption could in part be due to several recent pre-clinical efficacy studies demonstrating bitter melon potential to target obesity/type II diabetes-associated metabolic aberrations as well as its pre-clinical anti-cancer efficacy against various malignancies. The bioassay-guided fractionations have also classified the bitter melon chemical constituents based on their anti-diabetic or cytotoxic effects. Thus, by definition, these bitter melon constituents are at cross roads on the bioactivity parameters; they either have selective efficacy for correcting metabolic aberrations or targeting cancer cells, or have beneficial effects in both conditions. However, given the vast, though dispersed, literature reports on the bioactivity and beneficial attributes of bitter melon constituents, a comprehensive review on the bitter melon components and the overlapping beneficial attributes is lacking; our review attempts to fulfill these unmet needs. Importantly, the recent realization that there are common risk factors associated with obesity/type II diabetes-associated metabolic aberrations and cancer, this timely review focuses on the dual efficacy of bitter melon against the risk factors associated with both diseases that could potentially impact the course of malignancy to advanced stages. Furthermore, this review also addresses a significant gap in our knowledge regarding the bitter melon drug-drug interactions which can be predicted from the available reports on bitter melon effects on metabolism enzymes and drug transporters. This has important implications, given that a large proportion of individuals, taking bitter melon based supplements/phytochemical extracts/food based home-remedies, are also likely to be taking conventional therapeutic drugs at the same time. Accordingly, the comprehensively reviewed information here could be prudently translated to the clinical implications associated with any potential concerns regarding bitter melon consumption by cancer patients.

Bitter melon juice targets molecular mechanisms underlying gemcitabine resistance in pancreatic cancer cells

Pancreatic cancer (PanC) is one of the most lethal malignancies, and resistance towards gemcitabine, the front-line chemotherapy, is the main cause for dismal rate of survival in PanC patients; overcoming this resistance remains a major challenge to treat this deadly malignancy. Whereas several molecular mechanisms are known for gemcitabine resistance in PanC cells, altered metabolism and bioenergetics are not yet studied. Here, we compared metabolic and bioenergetic functions between gemcitabine-resistant (GR) and gemcitabine-sensitive (GS) PanC cells and underlying molecular mechanisms, together with efficacy of a natural agent bitter melon juice (BMJ). GR PanC cells showed distinct morphological features including spindle-shaped morphology and a decrease in E-cadherin expression. GR cells also showed higher ATP production with an increase in oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Molecular studies showed higher expression of glucose transporters (GLUT1 and 4) suggesting an increase in glucose uptake by GR cells. Importantly, GR cells showed a significant increase in Akt and ERK1/2 phosphorylation and their inhibition decreased cell viability, suggesting their role in survival and drug resistance of these cells. Recently, we reported strong efficacy of BMJ against a panel of GS cells in culture and nude mice, which we expanded here and found that BMJ was also effective in decreasing both Akt and ERK1/2 phosphorylation and viability of GR PanC cells. Overall, we have identified novel mechanisms of gemcitabine resistance in PanC cells which are targeted by BMJ. Considering the short survival in PanC patients, our findings could have high translational potential in controlling this deadly malignancy.

Effect of α, β momorcharin on viability, caspase activity, cytochrome c release and on cytosolic calcium levels in different cancer cell lines

A multitude of plants have been used extensively for the treatment of cancers throughout the world. The protein, α, β momorcharin has been extracted from the plant Momordica charantia (MC), and it possesses anti-cancer and anti-HIV properties similar to the crude water and methanol soluble extract of the plant. This study investigated the anti-cancer effects and the cellular mechanisms of action of α, β momocharin (200-800 μM) on 1321N1, Gos-3, U87-MG, Sk Mel, Corl-23 and Weri Rb-1 cancer cell lines compared to normal healthy L6 muscle cell line measuring cell viability using MTT assay kit, Caspase-3 and 9 activities, cytochrome c release and intracellular free calcium concentrations [Ca(2+)]i. The results show that α, β momorcharin can evoke significant dose-dependent (P < 0.05; Student's t test) decreases in the viability (increases in cell death) of 1321N1, Gos-3, U87-MG, Sk Mel, Corl-23 and Weri Rb-1 cancer cell lines compared to healthy L6 muscle cell line and untreated glioma cells. α, β momorcharin (800 μM) also evoked significant (P < 0.05) increases in caspase-3 and 9 activities and cytochrome c release. Similarly, α, β momorcharin elicited significant (P < 0.05) time-dependent elevation in [Ca(2+)]i in all five glioma cell lines compared to untreated cells. Together, the results have demonstrated that α, β momorcharin can exert its anti-cancer effect on different cancer cell lines by intracellular processes involving an insult to the mitochondria resulting in cellular calcium over loading, apoptosis, cytochrome release and subsequently, cell death.

Antileukemic Potential of Momordica charantia Seed Extracts on Human Myeloid Leukemic HL60 Cells

Momordica charantia (bitter gourd) has been used in the traditional system of medicine for the treatment of various diseases. Anticancer activity of M. charantia extracts has been demonstrated by numerous in vitro and in vivo studies. In the present study, we investigated the differentiation inducing potential of fractionated M. charantia seed extracts in human myeloid HL60 cells. We found that the HL60 cells treated with the fractionated seed extracts differentiated into granulocytic lineage as characterized by NBT staining, CD11b expression, and specific esterase activity. The differentiation inducing principle was found to be heat-stable, and organic in nature. The differentiation was accompanied by a downregulation of c-myc transcript, indicating the involvement of c-myc pathway, at least in part, in differentiation. Taken together these results indicate that fractionated extracts of M. charantia seeds possess differentiation inducing activity and therefore can be evaluated for their potential use in differentiation therapy for leukemia in combination with other inducers of differentiation.

Plant vermicides of Haitian Vodou show in vitro activity against larval hookworm

Haitian Vodou priests (houngans) and priestesses (mambos) use plant remedies to treat many illnesses, including intestinal parasite infections. The present study screened 12 plants used in Vodou treatments for intestinal parasites to detect in vitro activity against infective-stage larvae of the hookworm Ancylostoma caninum. Water-soluble extracts of 4 of the 12 plants inhibited serum-stimulated feeding by larval A. caninum in a dose-dependent manner. All 4 plant extracts inhibited feeding induced by the muscarinic agonist arecoline, suggesting that these plant extracts may inhibit the insulin-like signaling pathway involved in the recovery and resumption of development of arrested A. caninum larvae. These results indicate that at least some of the plants used in traditional Haitian medicine as vermifuges show activity against nematode physiological processes.

Pharmacological actions and potential uses of Momordica charantia: a review

Since ancient times, plants and herbal preparations have been used as medicine. Research carried out in last few decades has certified several such claims of use of several plants of traditional medicine. Popularity of Momordica charantia (MC) in various systems of traditional medicine for several ailments (antidiabetic, abortifacient, anthelmintic, contraceptive, dysmenorrhea, eczema, emmenagogue, antimalarial, galactagogue, gout, jaundice, abdominal pain, kidney (stone), laxative, leprosy, leucorrhea, piles, pneumonia, psoriasis, purgative, rheumatism, fever and scabies) focused the investigator's attention on this plant. Over 100 studies using modern techniques have authenticated its use in diabetes and its complications (nephropathy, cataract, insulin resistance), as antibacterial as well as antiviral agent (including HIV infection), as anthelmintic and abortifacient. Traditionally it has also been used in treating peptic ulcers, interestingly in a recent experimental studies have exhibited its potential against Helicobacter pylori. Most importantly, the studies have shown its efficacy in various cancers (lymphoid leukemia, lymphoma, choriocarcinoma, melanoma, breast cancer, skin tumor, prostatic cancer, squamous carcinoma of tongue and larynx, human bladder carcinomas and Hodgkin's disease). There are few reports available on clinical use of MC in diabetes and cancer patients that have shown promising results.

Effects of Momordica charantia fruit juice on islet morphology in the pancreas of the streptozotocin-diabetic rat

An investigation was made of the effect of Momordica charantia fruit juice on the distribution and number of alpha, beta and delta cells in the pancreas of streptozotocin (STZ)-induced diabetic rats using immunohistochemical methods. The results indicated that there was a significant (Student's t-test, P < 0.004) increase in the number of beta cells in M. charantia-treated animals when compared with untreated diabetics, however, their number was still significantly less than that obtained for normal rats. There was also a significant (P < 0.006) increase in the number of delta cells in STZ-diabetic rats compared to non-diabetic rats. This increase in the number of delta cells was not affected by M. charantia treatment. The number of alpha cells did not change significantly in M. charantia-treated rats when compared with untreated diabetic rats. Our results suggest that oral feeding of M. charantia fruit juice may have a role in the renewal of beta cells in STZ-diabetic rats or alternately may permit the recovery of partially destroyed beta cells.

Signal transduction: activation of the guanylate cyclase-cyclic guanosine-3'-5' monophosphate system by hormones and free radicals

Intracellular communication and transmission of messages for many hormones and free radicals occur after the hormones and free radicals bind to their receptors by enhancing the activity of guanylate cyclase, the enzyme that catalyzes the conversion of guanosine triphosphate to the intracellular messenger cyclic guanosine-3'-5' monophosphate (cyclic GMP). The guanylate cyclase-linked receptors exist intracellularly (ie, cytoplasmic) and in membrane-bound forms. Enhancement of guanylate cyclase by hormones or free radicals increases intracellular cyclic GMP, which closes cation channels in the kidney while activating cation channels in the retina and olfactory cilia, either directly or by cyclic GMP-dependent protein kinase. Cyclic GMP also has potent blood pressure lowering properties. Cyclic GMP promotes growth by increasing DNA, RNA, and protein synthesis. Overactivity of this system is observed in Traveler's diarrhea, whereas underactivity occurs in Chediak-Higashi syndrome in which lysosomal enzyme release and chemotaxis are defective and can be corrected in vitro by addition of cyclic GMP.

Anti-diabetic properties and phytochemistry of Momordica charantia L. (Cucurbitaceae)

Unripe fruit, seeds and aerial parts of Momordica charantia Linn. (Cucurbitaceae) have been used in various parts of the world to treat diabetes. Oral administration of the fruit juice or seed powder causes a reduction in fasting blood glucose and improves glucose tolerance in normal and diabetic animals and in humans. Animal and in vitro data support both insulin secretagogue and insulinomimetic activity of the fruit. However, enhanced insulin levels in vivo in response to its administration have not been observed. Although a wide range of compounds have been isolated from Momordica charantia, notably steroidal compounds and proteins, the orally active antidiabetic principle has not been adequately identified. A polypeptide, p-insulin, produces hypoglycaemic effects in humans and animals on subcutaneous injection, but oral activity is questionable. Other reported hypoglycaemic principles from Momordica charantia include the sterol glucoside mixture charantin (fruit) and the pyrimidine nucleoside vicine (seeds). However these are only effective at doses too high to account for all the activity of the plant extract. Principal toxicity of Momordica charantia in animals is to the liver and reproductive system. These effects have not been reported in humans despite widespread use of the fruit medicinally and as a vegetable.

The effects of dietary fiber from Lagenaria scineraria (yugao-melon) on colonic carcinogenesis in mice

BACKGROUND

The increasing trend of colon cancer in Japan is attributed to changes in dietary habits, that is, increased amounts of fat and decreased amounts of fiber in the diet. The effects of Japanese dietary fiber from Lagenaria scineraria (yugao-melon) on colonic carcinogenesis in mice were examined.

METHODS

Eighteen ICR mice in each group were fed with either a basal diet or a diet containing 5%, 10%, or 20% of yugao powder for 35 weeks. All the mice received a weekly intraperitoneal injection of 1,2-dimethylhydrazine (DMH), 10 mg/kg body weight for 10 weeks. The effects of yugao powder on the mucosal and luminal variables involved in colonic carcinogenesis were then compared with those of wheat bran in the mice without any carcinogen treatment.

RESULTS

The incidence of colon tumors (adenocarcinomas) was lower in the yugao powder diet groups than in the basal diet group at week 35 (24% vs. 50%, P < 0.05). The bile acid concentration in the colon was reduced in all the fiber diet groups except for the 5% yugao powder diet group. The colonic luminal pH acidified as yugao powder contents also increased in the yugao powder diet groups. The findings on the colonic short chain fatty acids, microflora, and mucosal fatty acids and ornithine decarboxylase activity were all inconsistent with a tendency to either develop or to inhibit carcinogenesis in both the fiber diet groups.

CONCLUSIONS

Dietary fiber from yugao-melon suppressed DMH-induced colonic carcinogenesis in mice by lowering the bile acid concentration and pH in the colon. The results of the luminal and mucosal variables examined also suggested that the mechanisms of action of yugao powder against colonic carcinogenesis differed from those of wheat brain.

Epidemiologic survey on lung cancer with respect to cigarette smoking and plant diet

This case-control study of lung cancer was based on a cross-sectional questionnaire survey of inpatients at 5 general hospitals in Okinawa, Japan, from 1982 to 1987. The purpose of the study was to clarify the relations of lung cancer to cigarette smoking and plant diet. Ingestion frequencies of 17 major dietary plants and/or herbs were obtained by means of a questionnaire interview. As eligible subjects for a case-control analysis, there were 673 respondents aged over 30 years with clear smoking history, age, sex and diagnosis. Psychiatric patients were excluded. Odds ratios of newly diagnosed lung cancer were calculated by the Mantel-Haenszel procedure. A pair consisted of a case and two controls which were selected randomly by using multivariate caliper matching. Sixty-four pairs matched for age (+/- 5) and sex showed a significantly high odds ratio of 2.9 (P less than 0.0005). However, three male groups who were categorized by the number of cigarettes smoked did not exhibit dose-dependency of lung cancer on smoking. Lung cancer was more prevalent in ex-smokers than in current smokers. Case-control analyses by male generations revealed that lung cancer incidence was age-dependent, and there was a clear dose-response relationship between smoking and lung cancer in males in their sixties. A case-control analysis of each of 17 edible plants based on 44 pairs who were matched for age (+/- 5), sex and smoking history demonstrated that the odds ratio of aloe (Aloe arborescens Mill var. natalensis Berger) was 0.5 (P less than 0.1), suggesting that the aloe may prevent human carcinogenesis at various sites.

B complex vitamins activate rat guanylate cyclase and increase cyclic GMP levels

Since B complex vitamins and the intracellular messenger cyclic guanosine monophosphate (GMP) have similar effects of promoting growth, DNA and protein synthesis, the present investigation was designed to determine if the B complex vitamins' mechanism of action might involve cyclic GMP. All of the B complex vitamins increased rat cyclic GMP tissue levels. The cause of these increased cyclic GMP levels was activation of the enzyme guanylate cyclase [E.C.4.6.1.2.] which was increased significantly (P less than 0.001) in a variety of tissues at the l nmol l-1 concentration of these vitamins. The maximal activation of this enzyme required the presence of manganese ion. The present investigation suggests that the guanylate cyclase-cyclic GMP system may play a role in the mechanism of action of B complex vitamins at the cellular level.

Cation-dependent vitamin D activation of human renal cortical guanylate cyclase

The objective of this investigation was to determine whether physiological levels of vitamin D and its metabolites have part of their mechanisms of action through stimulation of guanylate cyclase (EC 4.6.1.2). These sterols enhanced both soluble and particulate guanylate cyclase activities as well as cGMP levels two- to threefold in human and rat tissues. At a concentration of 1 nM, 1,25(OH)2D3 greater than 25(OH)D3 greater than vitamin D3 greater than 24,25(OH)2D3 = 25,26(OH)2D3 = vitamin D2. Dose-response curves revealed that maximal stimulation of guanylate cyclase by these sterols was at 1 nM and that there was no augmented guanylate cyclase activity at 0.01 nM. The precursors of vitamin D, cholesterol and 7-dehydrocholesterol, had no effect on guanylate cyclase activity. The activation of guanylate cyclase activity by the vitamin D sterols required the presence of manganese ion. Calcium was not as efficient as manganese in optimizing basal or hormone-stimulated guanylate cyclase activity. Vitamin D and its metabolites failed to stimulate adenylate cyclase (EC 4.6.1.1) activity. The data in this investigation suggest that guanylate cyclase may play a role in the mechanism of action of vitamin D at the cellular level.

Purification and characterization of a cytostatic factor with anti-viral activity from the bitter melon

We have previously reported that a crude aqueous extract of the bitter melon (Momordica charantia) has both cytostatic and cytotoxic activities, and is a competitive inhibitor of guanylate cyclase activity. This crude preparation kills human leukemic lymphocytes in a dose-dependent manner while not affecting the viability of normal human lymphocytes at these same doses. In this report we describe the purification and characterization of one of these cytostatic factors which also exhibits anti-viral activity. The partially purified factor was both cytostatic to BHK-21 cells and inhibitory to VSV plaque formation in a dose-dependent manner. This preparation was inhibitory to both viral and host cell RNA and protein synthesis as early as 30 min after addition to these samples. As determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), this purified factor is a single component with a molecular weight corresponding to 40,000 daltons. The factor is sensitive to boiling and to pre-treatments with trypsin, but not ribonuclease (RNAse), or deoxyribonuclease (DNAse). As determined by radioactive precursor uptake and incorporation studies, the purified factor inhibits both RNA and protein synthesis in intact tissue culture cells and inhibits protein synthesis in a cell-free wheat germ system. DNA synthesis was slightly stimulated. The purified factor is cytostatic for both BHK-21 and for the IM9 leukemic cell lines for at least 120 h. The cytostatic component had no effect on cellular cyclic GMP metabolism.

Purification and characterization of a cytostatic factor with anti-viral activity from the bitter melon

We have previously reported that a crude aqueous extract of the bitter melon (Momordica charantia) has both cytostatic and cytotoxic activities, and is a competitive inhibitor of guanylate cyclase activity. This crude preparation kills human leukemic lymphocytes in a dose-dependent manner while not affecting the viability of normal human lymphocytes at these same doses. In this report we describe the purification and characterization of one of these cytostatic factors which also exhibits anti-viral activity. The partially purified factor was both cytostatic to BHK-21 cells and inhibitory to VSV plaque formation in a dose-dependent manner. This preparation was inhibitory to both viral and host cell RNA and protein synthesis as early as 30 min after addition to these samples. As determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), this purified factor is a single component with a molecular weight corresponding to 40,000 daltons. The factor is sensitive to boiling and to pre-treatments with trypsin, but not ribonuclease (RNAse), or deoxyribonuclease (DNAse). As determined by radioactive precursor uptake and incorporation studies, the purified factor inhibits both RNA and protein synthesis in intact tissue culture cells and inhibits protein synthesis in a cell-free wheat germ system. DNA synthesis was slightly stimulated. The purified factor is cytostatic for both BHK-21 and for the IM9 leukemic cell lines for at least 120 h. The cytostatic component had no effect on cellular cyclic GMP metabolism.

Ultracytochemical localization of guanylate cyclase in the oviduct of estrogen-stimulated rat

Many reports have indicated that estrogens increase uterine guanosine 3',5'-cyclic monophosphate (cGMP) levels via increasing the activity of guanylate cyclase. In the present study, guanylate cyclase activity was studied cytochemically in the oviduct of immature rats 24 hours after one or two doses (20 micrograms/kg, subcutaneously) of diethylstilbestrol (DES), one dose per day. The reaction product indicating guanylate cyclase was localized in the plasma membrane of epithelial cells, endothelial cells, and smooth muscle cells of all DES-treated animals, but was absent from those of the vehicle control immature rats. The Golgi saccules of secretory cells and the periciliary membrane of ciliated cells were stained for the enzyme 24 hours after the first and second dose of DES, but the activity seemed diminished 24 hours after the second dose. Likewise, reaction product indicating guanylate cyclase was more prominent in the plasma membrane of epithelial cells of animals treated with one dose of DES than those animals treated with two doses of DES. However, in the endothelial and smooth muscle cells, guanylate cyclase activity increased after two doses of the estrogen. Further, pinocytotic vesicles or caveolae in these cells were also strongly stained for the enzyme after one and two doses of DES. These findings confirm the suggestion that guanylate cyclase plays a significant role in the growth, differentiation, and function (secretion and transport) of the oviduct.

Purification and characterization of a cytostatic factor from the bitter melon Momordica charantia

In this report we describe the purification and characterization of a cytostatic factor from the bitter melon (Momordica charantia). As determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), this purified factor is a single component with an apparent molecular weight of 11,000. The factor is not sensitive to boiling or to pretreatments with trypsin, ribonuclease (RNAse), or deoxyribonuclease (DNAse). As determined by radioactive precursor uptake studies, the purified factor preferentially inhibits RNA synthesis in intact tissue culture cells. Some inhibition of protein synthesis and DNA synthesis also occurs. The factor is preferentially cytostatic for IM9 human leukemic lymphocytes when compared to normal human peripheral blood lymphocytes.

Purified Clostridium difficile cytotoxin stimulates guanylate cyclase activity and inhibits adenylate cyclase activity

Antibiotic-associated pseudomembranous colitis has been linked with Clostridium difficile toxin. We examined the effect of toxins from four strains of C. difficile isolated from patients with pseudomembranous colitis on colonic adenylate (EC 4.6.1.1) and guanylate cyclase (EC 4.6.1.2) activities. Partially purified toxins had a cytotoxic effect on hamster fibroblasts in culture at a concentration of 10 ng/ml. Likewise, these toxins enhanced colonic guanylate cyclase activity two- to threefold, with the maximal stimulation being at 10 ng/ml. These toxins also enhanced guanylate cyclase activity in ileum, cecum, and duodenum. Both the cytotoxic activity on hamster fibroblasts and the enhancement of hamster guanylate cyclase activity were inhibited by antiserum to C. difficile toxin. These same toxins inhibited adenylate cyclase activity at a 100-ng/ml concentration, but had no effect at 10 ng/ml. They also had no effect at any concentration on colonic Na+-K+ adenosine triphosphatase. To be sure that the findings were not due to a contaminant, a purified C. difficile cytotoxin was used, and the same findings were found with the pure cytotoxin (at a 100-fold-lower concentration). The data suggest that activation of guanylate cyclase may be a factor in the pathogenesis of antimicrobial-associated pseudomembranous colitis.

Testosterone and its precursors and metabolites enhance guanylate cyclase activity

Both testosterone and cyclic GMP stimulate DNA synthesis. Because cyclic GMP and testosterone seem to have similar actions, the objective of this investigation was to determine if testosterone and its precursors might have part of their mechanism of action through stimulation of guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2], the enzyme that catalyzes the formation of cyclic GMP from GTP. The precursors--namely, progesterone, pregnenolone, 17 alpha-progesterone, 17 alpha-hydroxypregnenolone, androstenedione, and dehydroepiandrosterone--caused a 2- to 3 1/2-fold enhancement of guanylate cyclase activity in rat liver, kidney, skeletal muscle, and ventral prostate at a concentration of 1 microM. These precursors are generated from cholesterol, which had no effect itself on guanylate cyclase activity. Testosterone, 19-nortestosterone, 17-methyltestosterone, and 5 alpha-dihydrotestosterone enhanced guanylate cyclase activity 2- to 5-fold in the same tissues at 1 microM. Etiocholanolone, androsterone, and epiandrosterone, metabolites of testosterone metabolism, enhanced guanylate cyclase activity 1 1/2- to 2-fold at this same concentration. Dose-response relationships revealed that testosterone and its precursors and metabolites had their maximal effect at 1 microM but still had some effect at 0.001 microM. The data in this investigation suggest that the guanylate cyclase-cyclic GMP system plays a role in the mechanism of action of testosterone and its precursors.