Walid A. Al-Turk

Glutathione levels in hepatic and extrahepatic tissues of mice as a function of age

Glutathione is the most abundant thiol-containing component in living cells and is believed to play an important role as an antioxidant. We have examined the levels of reduced, oxidized, and total glutathione in liver, blood, kidneys, and intestinal mucosa of mice as a function of age. Reduced glutathione levels decreased in kidneys, Intestinal mucosa, and blood while total glutathione levels decreased in all tissue with advanced age. Highest concentrations of reduced glutathione per μg protein were present in liver and intestinal mucosa. Our results support the hypothesis that a decrease in reduced glutathione may contribute to changes associated with aging as well as to the increased susceptibility to disease processes which occur with advanced age.

Changes in glutathione and glutathione metabolizing enzymes in erythrocytes and lymphocytes of mice as a function of age

Changes in reduced glutathione levels in liver, lung and whole blood of female Swiss-Webster mice with age were determined. In addition, glutathione content, and glutathione S-transferase and glutathione reductase activities of erythrocytes and lymphocytes of mice as a function of age were examined. Reduced glutathione content increased in liver, lung, whole blood, erythrocytes and lymphocytes with age from 3 to 9 months, reached a maximum level at 9 months of age and decreased thereafter with advanced age in all tissues. Glutathione S-transferase and glutathione reductase activities in erythrocytes and lymphocytes increased with age from 3 to 9 months, reached maximum activities at 9 months and decreased thereafter with advanced age. The glutathione content of erythrocytes from animals 18 months of age decreased by 56% as compared to 9 month old mice, while the activities of glutathione S-transferase and glutathione reductase decreased by 56 and 48%, respectively, over the same age span.

Glutathione S-transferase activity in liver, lung and intestinal mucosa of aging female mice.

1. Changes in the activity of glutathione S-transferase (GST) in liver, lungs and intestinal mucosa of female Swiss-Webster mice with age were determined. 2. GST activity increased with age from 1 to 9 months, reached a maximum activity at 9 months and decreased thereafter with advanced age in all three tissues. 3. GST activity decreased by approximately 75% in liver between 9 and 18 months, with decreases of 65 and 64% occurring over the same time period for lung and intestinal mucosa, respectively.

Altered drug metabolism in hepatic and extrahepatic tissues in mice as a function of age

An increase in the susceptibility to drugs is known to occur with advanced age. Several possible explanations for this phenomenon exist, but the exact cause has not been determined. Aryl hydrocarbon hydroxylase (AHH), 7-ethoxycoumarin O-deethylase (ECD) and aniline hydroxylase activities of hepatic and extrahepatic tissues as well as hepatic cytochrome P-450 content of female Swiss Webster mice at 1, 3, 6, 9, 12, 15 and 18 months of age were examined. AHH activity in liver and intestine reached a maximum at 6 mo. of age and began to decline thereafter. No change in pulmonary AHH activity was observed with age. ECD activity in liver as well as lungs was maximal at 6 mo. of age and decreased thereafter. Hepatic aniline hydroxylase activity exhibited over a 700% increase between one to six mo. of age, and declined by approximately 52% by 15 mo. of age as compared to peak activity. Hepatic cytochrome P-450 content was highest at 3 mo. of age and significantly decreased by 12 mo. The results demonstrate that decreases in microsomal mixed function monooxygenase activities do occur with advanced age and may contribute to a decreased rate of metabolism and increased susceptibility to drugs and other foreign chemicals with age.

Altered Activities of Hepatic and Extrahepatic Microsomal Mixed Function Oxidase Enzymes in Diabetic and Adrenalectomized Diabetic Rats

Microsomal aryl hydrocarbon hydroxylase (AHH) and 7-ethoxycoumarin-O-deethylase (ECD) activities were determined in liver, lung and intestine of control, streptozotocin(STZ)-diabetic, and diabetic-adrenalectomized male and female rats. Hepatic cytochrome P-450 content was also determined. The diabetic state reduced hepatic AHH activity and increased ECD activity in control male rats, and failed to do so in the adrenalectomized male rats. The diabetic state increased hepatic AHH and ECD activities in the control female rats, while in the adrenalectomized female rats the activities of both enzymes were decreased compared to the control diabetic rats. STZ-induced diabetes produced a decrease in pulmonary AHH and ECD activities and increased intestinal AHH and ECD activities in both sexes. The diabetic state in the adrenalectomized rats resulted in further reduction in pulmonary AHH and ECD activities in both sexes, but failed to increase the intestinal AHH activity only in the female rat. Hepatic cytochrome P-450 contents were increased in the female but not male adrenalectomized rats when treated with STZ. The effects of STZ-induced diabetes in adrenalectomized rats on AHH, ECD and hepatic cytochrome P-450 content in liver, lung and intestine depended upon sex of animal, substrate and tissue.

Activities of hepatic and extrahepatic microsomal mixed function oxidase enzymes in diabetic and gonadectomized-diabetic rats

Abstract 1. 1. Streptozotocin (STZ)-induced diabetes results in a decrease in hepatic aryl hydrocarbon hydroxylase (AHH) activity in male rats and an increase in female rats, while hepatic 7-ethoxycoumarin 0-deethylase (ECD) activity is increased in both sexes. 2. 2. In castrated male rats, induction of the diabetic state resulted in a further decrease in hepatic AHH activity. In diabetic female rats, ovariectomy did not alter hepatic AHH or ECD activities. 3. 3. STZ-induced diabetes produced an increase in hepatic cytochrome P-450 content. The diabetic state failed to produce an increase in hepatic cytochrome P-450 content of castrated male animals, and only a small increase in castrated female rats. 4. 4. AHH and ECD activities are decreased in lungs of STZ-induced diabetic male and female rats. In diabetic-castrated rats a further decrease in pulmonary ECD activity occurs in both sexes, and in the AHH activity of female rats. 5. 5. The induction of diabetes with STZ increased intestinal AHH and ECD activities in both sexes. In diabetic-castrated rats, intestinal ECD activities were identical to the activities in diabetic male and female animals, while intestinal AHH activities were lower than the activities in diabetic animals but still significantly higher than in control animals of both sexes.

Chronic phenytoin administration and the hepatic mixed function oxidase system in female rats

The long term effects of phenytoin administration on mixed function oxidase activities and serum estradiol in female rats were examined. No induction of hepatic mixed function oxidases was seen until 8 days after the administration of 100 mg phenytoin/kg/day either orally or intraperitoneally. Maximum increase in aniline hydroxylase, aryl hydrocarbon hydroxylase (AHH) and ethylmorphine-N-deethylase activities occurred between days 8 and 16 of treatment and decreased thereafter. No induction of lung or intestinal AHH activity was observed. Serum levels of estradiol were significantly decreased after 16 days of phenytoin treatment. Maximal increases in hepatic cytochrome P-450 and cytochrome c reductase occurred after 8-16 days of treatment. Furthermore, pentobarbital sleeping times were shortest after 16 days of phenytoin administration. The activities of all enzymes after 32 days of phenytoin treatment were less than at the peak activities at 8-16 days.

Diminished Conjugation of Products of Mixed-Function Oxidation in Perfused Livers from Hypophysectomized Rats

The rates of metabolism of 7-ethoxycoumarin and subsequent conjugation of 7-hydroxycoumarin were studied in perfused livers from hypophysectomized or sham-operated control rats. Rates of 7-ethoxycoumarin O-deethylation were higher both in perfused livers and microsomes from hypophysectomized compared to sham-operated controls. However, conjugation of 7-hydroxycoumarin formed from 7-ethoxycoumarin was markedly decreased by hypophysectomy. p-Nitrophenol conjugation was also impaired in perfused livers from hypophysectomized rats. During infusion of 59-65 microM of p-nitrophenol into hypophysectomized livers, rates of glucuronidation were diminished by 45% (6.83 +/- 0.49 to 3.78 +/- 0.31 mumol/g/h) and rates of sulfation were decreased by 50% (1.25 +/- 0.12 to 0.62 +/- 0.07 mumol/g/h). Phenol sulfotransferase activity was decreased 57% by hypophysectomy, which is the likely explanation for the decrease in sulfate conjugation. However, hypophysectomy did not affect glucuronyltransferase activity. Perfused livers from hypophysectomized rats released glucose, pyruvate and lactate at lower rates than livers from sham-operated rats. Furthermore, infusion of glucose into perfused livers from hypophysectomized rats, but not sham-operated controls, increased the rate of conjugation. The results demonstrate that hypophysectomy decreased rates of conjugation in perfused livers, and that the decreased glucuronidation rates are probably the result of diminished carbohydrate reserves.

EFFECTS OF ESTRONE, ESTRADIOL AND ESTRIOL PRETREATMENT ON HEPATIC, LUNG, AND INTESTINAL ARYL HYDROCARBON HYDROXYLASE ACTIVITIES IN FEMALE RATS

Forty day old female rats were given 1 mg/kg estrone (E1), estradiol (E2), or estriol (E3), i.p., acutely or chronically. The data indicate that alterations of AHH activity are organ specific and depend upon the estrogen administered as well as the duration of steroid pretreatment. The differences observed may be explained on the basis of estrogen receptors.

In vitro screening of the effect of hydrazine derivatives on hepatic aryl hydrocarbon hydroxylase activity

1. The effect of hydrazine derivatives on the in vitro hepatic microsomal aryl hydrocarbon hydroxylase activity was examined using Sprague-Dawley male rats. 2. All hydrazine derivatives examined have some degree of inhibition on hepatic aryl hydrocarbon hydroxylase activity. 3. The inhibitory effect is concentration dependent and is also dependent on the structural substitution of the hydrazines. The more lipophilic the derivative, the more potent the inhibition of aryl hydrocarbon hydroxylase activity.