Marian E. Addy

SPECIES CHARACTERISTICS OF HEPATIC BIOTRANSFORMATION ENZYMES IN TWO TROPICAL FRESHWATER TELEOSTS, TILAPIA (OREOCHROMIS NILOTICUS) AND MUDFISH (CLARIAS ANGUILLARIS)

Abstract Tilapia ( Oreochromis niloticus ) and mudfish ( Clarias anguillaris ) were given a single intraperitoneal injection of β-naphthoflavone (BNF, 50 mg/kg) and Clophen A50 (Clo A50, 20 mg/kg). Hepatic levels of CYP1A protein, 7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST) and UDP-glucuronasyl transferase (UDP-GT) activities were determined at days 3 and 10 after treatment. Highest levels of EROD activity (5–6-fold) and CYP1A protein (3–5-fold) were observed in both species at day 3 on treatment with BNF. The same treatment also increased GST and UDP-GT activities in mudfish at day 3, but only UDP-GT activity was induced in tilapia at day 10. In tilapia treated with Clo A50, EROD activity was highest at day 3, whereas CYP1A protein level, GST and UDP-GT activities were highest at day 10. In mudfish, Clo A50 appeared to inhibit EROD activity, but CYP1A protein level was increased at day 10, whereas GST and UDP-GT activities reached highest levels at day 3. The control EROD levels did not differ significantly between the species, but control GST levels were three to five times higher in tilapia, whereas those of UDP-GT were six times higher in mudfish. Although there are many common features in the hepatic xenobiotic biotransformation systems of the two freshwater teleosts, a number of species characteristics exist; most importantly, the differences in response to polychlorinated biphenyls and the different temporal pattern of induction response. These factors should be taken into account when using these species in studies of xenobiotic biotransformation and biomarker responses in tropical freshwater fish.

Extract of Ocimum canum lowers blood glucose and facilitates insulin release by isolated pancreatic β-islet cells

Aqueous extract of Ocimum canum Sim, (Lamiaceae) is used by some Ghanaians to manage diabetes mellitus. In vivo modulation of levels of fasting blood glucose by 0. canum extract was evaluated in type-II diabetes mellitus using the C57BL/KsJ db/db genetically diabetic animal model, and its effects on glucose-stimulated insulin release in vitro were monitored using isolated rat pancreatic beta-islet cells. The results showed that fasting blood glucose levels and body weight decreased significantly (p < 0.05) in diabetic and non-diabetic C57BL/KsJ mice, which were administered aqueous extract of 0. canum. In vitro, the 0. canum extract significantly enhanced insulin release from isolated rat pancreatic beta-islet cells. Insulin release was found to be dependent on glucose concentration and increased with increasing O. canum concentration in the incubation medium up to an optimum extract concentration of 0.03 mg/ml. Release of the hormone decreased beyond this concentration of extract in the medium. Addition to the medium of Desmodium adscendens, a plant preparation used to manage inflammatory disorders, did not increase but rather inhibited insulin secretion by the pancreatic beta-islet cells. These results could explain the use of 0. canum in Ghanaian folk medicine to manage diabetes mellitus.

Effects of the extracts of Desmodium adscendens on anaphylaxis

Desmodium adscendens, used by herbalists in Ghana for the treatment of asthma, is anti-anaphylactic in vitro. As the plant material is administered orally, in vivo studies of its anti-anaphylactic property were undertaken using the guinea-pig. The results show that both aqueous and ethanolic extracts of D. adscendens, when taken orally, reduce anaphylactic contractions, interfere with histamine-induced contractions, and reduce the amount of smooth muscle stimulating substances released from lung tissue of guinea pigs.

Dose-response effects of Desmodium adscendens aqueous extract on histamine response, content and anaphylactic reactions in the guinea pig

Different concentrations of a hot water extract of Desmodium adscendens, a plant used in Ghana to control asthmatic attacks, were used in drinking water to evaluate the plants anti-anaphylactic properties in guinea pigs. The results show that the extracts inhibition of histamine-induced ileal contraction is largely competitive and that its effect of reducing lung histamine content is dose-dependent. The results also show that the extract causes a dose-dependent reduction in the amount of spasmogens released anaphylactically and in anaphylactic-induced contraction of ileal muscle.

Effect of Desmodium adscendens fraction 3 on contractions of respiratory smooth muscle.

The third flash chromatography fraction prepared from an aqueous extract of Desmodium adscendens leaves (DAF3) was evaluated for pharmacological activity using contractions of tracheal spirals and lung parenchymal strips caused by ovalbumin, arachidonic acid, histamine and carbachol. DAF3 inhibited both the early and late phases of antigen-induced contractions of both tissues dose-dependently, but had no effect on arachidonic-induced contractions. With tracheal spirals, the inhibition occurred whether the tissue was pretreated with indomethacin or not. On tracheal spirals, the maximum contraction (Emax) caused by histamine and carbachol were enhanced, but the pD2 value for histamine was not affected while that for carbachol was decreased. DAF3 had no effect on Emax or pD2 values for these agonists on lung parenchymal strips. The results suggest that DAF3 may inhibit the release of free arachidonic acid.

Aqueous extract of ocimum canum decreases levels of fasting blood glucose and free radicals and increases antiatherogenic lipid levels in mice

The basis for managing diabetes mellitus with aqueous extract of Ocimum canum Sim (Lamiaceae), in Ghana was investigated in diabetic and normoglycemic mice. In the diabetic mice, fasting blood glucose decreased by 60% compared to 10% in control mice after 13 weeks of extract administration. Body weight, serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) decreased while serum high-density lipoprotein cholesterol (HDL-C) increased in the extract-treated group. In vitro hydroxyl (OH) and superoxide (O2) radical formation, and lipid peroxidation of isolated human LDL and mouse liver homogenates decreased in extract-treated experimental systems. These findings justify the use of O. canum extract as an antidiabetic folk medicine.

In vitro screening for the anti-anaphylactic agent in Thonningia sanguined

Thonningia sanguinea, used prophylactically against bronchial asthma, is anti-anaphylactic and anti-asthmatic in guinea pigs when given orally. The aqueous extract of the plant and its fractions were screened in vitro for their effects on anaphylactic- and histamine-induced contractions, and the results compared with those obtained in vivo when the whole extract was administered orally. The comparison showed similar anti-anaphylactic properties of the plant material in the two systems of administration, but the effects on histamine-induced contractions differed from the in vivo ones, suggesting that the anaphylactic assay system should be preferred for the screening in vitro. The anti-anaphylactic substance(s) extracted into n-butanol. The active portions of the extracted components appeared to be stable to acid digestion. Thin layer chromatographic analysis of the butanol extract and preliminary chemical analysis suggest that these substances are polyhydroxy/phenolic in nature.