MODULATION OF HEPATIC CYP2A1, CYP2C11, AND CYP3A9 EXPRESSION IN ADULT RATS BY NEONATAL ADMINISTRATION OF TAMOXIFEN

This paper is available online at http://www.dmd.org ABSTRACT: To examine the effect of neonatal administration of tamoxifen on adult expression of hepatic cytochrome P-450 (CYP) enzymes and steroid 5␣-reductase, male and female Sprague-Dawley rats were injected s.c. with tamoxifen (20 g) or peanut oil (control) once daily at days 1 to 5 of age and sacrificed at 3 months of age. Neonatal tamoxifen treatment did not affect b.wt. or liver weight of adult male and female rats, but decreased testicular weight by approximately 40% in adult male rats. Neonatal administration of tamoxifen decreased hepatic microsomal testosterone 6␤-and 7␣-hydroxylase activities in adult female rats whereas it did not alter steroid 5␣-reductase activity. The same treatment increased testosterone 7␣-hydroxylase activity, but did not affect testosterone 6␤-hydroxylase or steroid 5␣-reductase activity in adult male rats. Immunoblot analysis indicated that neonatal tamoxifen treatment decreased CYP2C11 protein level by 26% and increased CYP2A1 protein content by 2.6-fold in adult male rats, whereas it had no effect on CYP3A or CYP2B protein expression. The reduction in the CYP3A-mediated testosterone 6␤-hydroxylase activity in adult female rats was accompanied by a decrease in CYP3A9 mRNA expression. Analysis of serum hormone levels indicated that neonatal exposure to tamoxifen resulted in a decrease in serum 17␤-estradiol concentration in adult female rats, whereas it did not alter serum testosterone concentration in adult male rats. In summary, treatment of neonatal rats with tamoxifen produced a longlasting effect on hepatic CYP2A1, CYP2C11, and CYP3A9 expression in addition to testicular weight and serum 17␤-estradiol concentration

A study of some pharmacological properties of certain alpha-glyceryl ethers.

The alpha-glyceryl ethers (AGE) are widely distributed in nature, occurring in many marine organisms, land animals, plants, and humans. A series of preliminary experiments was begun to determine whether these compounds possessed possible pharmacological actions against inflammation. Anti-inflammatory tests utilized both the granuloma pouch and cotton pellet granulation methods. Possible glucocorticoid activity was checked by measuring liver glycogen deposition. The effects of AGE on growth and weight of the animals was also noted. Neither selachyl dihemisuccinate sodium (selachyl DHSS) nor selachyl alcohol decreased the exudate formation in the granuloma pouch experiments, although excellent results were obtained with hydrocortisone. The high dose of the AGE was the equivalent of ten milligrams; low doses were three hundred and six hundred micrograms. Routes of administration used were oral, intraperitoneal, and subcutaneous. In the cotton pellet granuloma test, some indication of anti-inflammatory activity was obtained, in accordance with previous results in this and other laboratories. Selachyl DHSS decreased granulation tissue formation by only 11.7% in growing rats, which is not significant; however, in mature rats, there was a decrease of 29.5%. The dosage used in this series was 30 milligrams per kilogram daily by the subcutaneous route, A definite and comparatively large increase in liver glycogen deposition was observed in rats allowed to eat freely, when given selachyl DHSS subcutaneously. These glycogen values were decreased radically by a paired feeding study in which the treated rats were allowed to eat only the same amount of food as their paired control animal. Thus food intake appears to be one of the factors responsible for the increased glycogen storage. The AGE appear to affect growth only by the Intraperitoneal route of administration. In this case, the growth of rats was retarded by 29.6%. It was also noted that these animals ate somewhat less food than the controls, although this did not appear to be an important enough difference to account for the lack of weight gain. Throughout these experiments one of the most notable observations was a lack of uniformity of the results. Factors which appeared to cause a variability in the outcome of tests included the age of the animals, length of time of preoperative housing in new quarters, route of administration, and dosage. A non-linear relationship between dose and effect appears probable.Medicine, Faculty ofAnesthesiology, Pharmacology and Therapeutics, Department ofGraduat

Some studies on enzymes involved in glycogen catabolism in nervous tissue

Although the quantity of glycogen in nervous tissue is small, in recent years it has been found that there is a significantly high turnover rate of this polysaccharide. Glycogen is present in sympathetic ganglia, midbrain structures, white matter, and synaptic regions. The enzymes of glycogen synthesis and breakdown exist in brain in high concentrations, which suggests that glycogenolysis may be coupled in some way to the energy-requiring processes concerned with electrical activity. In this thesis, the occurrence and activity of phosphorylase a, phosphorylase b kinase and phosphofructokinase were determined in peripheral and central nerve tissue, an attempt to purify phosphorylase b kinase was made, and the mechanisms controlling the activity of the brain kinase were studied. These experiments were carried out in an effort to learn more about the importance of glycogenolysis in the nervous system and the factors which control it. The results of a survey of dog nerve tissue and some experiments on rabbit tissue indicated that the enzyme levels in brain, superior cervical and stellate ganglia were comparable to those in heart. Other peripheral nerve tissue has approximately one-tenth the level found in brain. Heavily myelinated axonal tissue contained higher phosphorylase activity and much higher kinase activity than axons with relatively little myelination. It is suggested that glycogenolysis is likely to be concerned with synaptic transmission and Schwann cell metabolism. Attempts to purify one of the controlling enzymes in glycogenolysis, phosphorylase b kinase, from brain tissue were hampered by the instability of the enzyme and the consequent loss of activity that occurred at each purification step. A modest 3.0 to 3.5-fold purification was achieved by differential ultracentrifugation, freezing and thawing of the 100,000 x g precipitate, and a 0-35 per cent ammonium sulfate fractionation at pH 5.7. The enzyme exhibited increased stability when stored in 50 per cent glycerol at -18°, especially when it was present in a more purified state, but other attempts to increase the stability of the kinase met with little success. The maximum activity of brain phosphorylase b kinase occurred between pH 8.75 and 8.9, and a significant activity was noted at pH 7.0, which is somewhat different from that found in other tissues. However, the brain kinase is activated by mechanisms similar to those found for skeletal and cardiac muscle. The activity at pH 6.8 is increased by preincubation with Ca⁺⁺, and further increased by the addition of rabbit skeletal muscle calcium-activating factor. This is partially prevented by beef heart calcium inhibitory factor. ATP-Mg⁺⁺ and cyclic AMP also cause activation of the brain kinase. The total activation of the brain enzyme appeared much lower than that found in skeletal or cardiac muscle due to the already high activity at pH 7.0. Experiments designed to produce an accurate value for the pH 6.8/8.2 ratios of kinase activity utilized freezing of mouse brain in vivo in liquid Freon cooled to its freezing point. The value of 0.44 obtained from these procedures was similar to, or slightly higher than, the ratios in rabbit and beef brain. The kinase was not inactivated by room temperature incubation for two hours, although similar treatment would convert phosphorylase to its inactive form. The possibility remains that the pH 7.0 activity is artificially high, assuming the freezing techniques used are not fast enough. Otherwise, the high enzymatic activity may be due to the continuous electrical activity present in the brain. The possibility that glycogen catabolism is a more important source of energy in the nervous system than previously thought is supported by the high levels of enzymatic activity and similar phosphorylase b kinase control mechanisms to those in other tissues.Medicine, Faculty ofAnesthesiology, Pharmacology and Therapeutics, Department ofGraduat

2-l407$02.00/0 DRUG METABOLISM AND DlsposmoN EFFECT OF CIMETIDINE ON HEPATIC CYTOCHROME P450: EVIDENCE FOR FORMATION OF A METABOLITE-INTERMEDIATE COMPLEX

ABSTRACT: Cimetidine is an inhibitor of hepatic cytochrome P450 (CYP) in vivo and in vitro in both rats and humans. However

Food intake, conversion efficiency, and feeding behaviour of tobacco hornworm caterpillars given artificial diet of varying nutrient and water content

Fifth stadium tobacco hornworm caterpillars, Manduca sexta (L.), given artificial diet diluted to varying extents with either cellulose or water compensated for the food's reduced nutrient content by eating more of it. This compensation was, however, in most cases not sufficient to maintain normal growth rates. When the water content of the diet was reduced, the insects ate less than the usual fresh weight of food but maintained their intake of nutrients. Nevertheless, growth rate was impaired. The insects were better able to compensate for dilution of their food with water than with cellulose. The efficiency of conversion of ingested food (ECI) was decreased when the diet was adulterated with cellulose. At moderate dilution (50% nutrient) this was due mostly to decreased approximate digestibility (AD), but at greater dilution (25% and 10% nutrient content) the efficiency of conversion of digested food (ECD) was decreased. ECI was maintained when the water content of the diet was increased to give 50% nutrient concentration, but was decreased when water content was changed more radically (200%, 25% and 10% nutrient diets). This was due mostly to increased metabolic costs (decreased ECD) in all cases. The retention time of food in the gut was progressively decreased (i.e. speed of passage was increased) as nutrients were replaced by cellulose. By contrast, dilution of the diet with water resulted in only slight changes in retention time, except at extreme dilution (10% nutrient content) when retention time was reduced. Compensation of food intake was achieved by spending more (or less) time eating. Video analysis of feeding behaviour showed that there were significant changes in the length of feeding bouts and of interfeed gaps when caterpillars fed on diets of altered composition. For diets diluted with cellulose, changes in bout length and bout frequency contributed substantially to the increased time spent feeding on the adulterated food. For diets diluted with water, however, almost all of the compensatory change in behaviour was due to increased bout length, with bout frequency affected only slightly. This suggests that volumetric feedback contributes principally to the termination of feeding bouts in caterpillars, while nutrient flow may affect both the initiation and termination of feeding.W. A. Timmins, K. Bellward, A. J. Stamp and S. E. Reynold