Xenobiotica the fate of foreign compounds in biological systems
ISSN: 0049-8254 (Print) 1366-5928 (Online) Journal homepage: http://www.tandfonline.com/loi/ixen20
Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from StreptozotocinDiabetic Female Rats L. A. Reinke, S. J. Stohs & H. Rosenberg To cite this article: L. A. Reinke, S. J. Stohs & H. Rosenberg (1978) Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from Streptozotocin-Diabetic Female Rats, Xenobiotica, 8:12, 769-778, DOI: 10.3109/00498257809069590 To link to this article: http://dx.doi.org/10.3109/00498257809069590
Published online: 22 Sep 2008.
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Date: 21 March 2016, At: 19:08
XENOBIOTICA,
1979, VOL. 8, NO. 12, 769-778
Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from Streptozotocin-Diabetic Female Rats L. A. REINKE, S. J. STOHS and H. ROSENBERG Department of Biomedicinal Chemistry, College of Pharmacy, University of Nebraska Medical Center, 42nd and Dewey Avenue, Omaha, Nebraska 68105, U.S.A.
Downloaded by [RMIT University Library] at 19:08 21 March 2016
(Received 13 February 1978; revised 5 September 1978)
1. In streptozotocin-induced diabetic male rats, hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activity was depressed to less than control values, but was increased in microsomes from diabetic female rats. Insulin treatment of diabetic animals returned the altered AHH activity to control values in both sexes of rats. 2. Hepatic microsomal AHH activity was increased over control values in both sexes of diabetic mice.
3. Protection of female rats from the diabetogenic effects of streptozotocin by nicotinamide pretreatment also prevented the increase in AHH activity observed in unprotected animals. 4. Treatment of control and diabetic female rats with S-methylcholanthrene resulted in larger increases in hepatic AHH activity in control animals, but similar increases in cytochrome P-448 content occurred in both treatment groups.
5 . Differential stimulatory or inhibitory effects on AHH activity were observed after the addition of SKF 525-A, metyrapone, and rotenone to hepatic microsomes in vitro from control and diabetic female rats. However, similar stimulatory responses in AHH activity were observed after addition of cc-naphthoflavone to microsomes from both treatment groups.
Introduction We have previously observed a sex-dependent eRect of experimental diabetes on mixed-function mono-oxygenase enzymes in the rat (Reinke et al., 1978). I n streptozotocin (STZ) diabetic male rats, we noted a decrease from control values in hepatic microsomal aminopyrine N-demethylase activity, but an increased aniline hydroxylase activity and cytochrome P-450 content. I n diabetic female rats, aminopyrine N-demethylase activity, aniline hydroxylase activity, biphenyl 4-hydroxylase activity and cytochrome P-450 content were all increased over control values. These observations are consistent with the majority of previous reports involving studies on alloxan-diabetic animals (Dixon et al., 1961, 1963; Kato & Gillette, 1965; Kato & Takahashi, 1969; Kato et al., 1968, 1970 a, b). T h e metabolism of aminopyrine and aniline is thought to be mediated by separate cytochrome P-450 forms (Conney & Kuntzman, 1971 ; Kato et ul., 1969). Therefore, the differential effects of experimental diabetes on these two enzymic activities suggest that the insulin-deficient state may favour the formation of a specific cytochrome form, for example, one favouring aniline hydroxylation. I n addition, Kato has demonstrated that administration of 3-methylcholanthrene to male and female rats produces sex-dependent changes in drug-metabolizing activity which are qualitatively similar to the changes discussed above in experimentally-induced diabetes (Kato et ul., 1969; Kato & Takayanagi, 1968). X.B.
3D
770
L. A. Reinke et al.
T h e formation of cytochrome P-448 in hepatic microsomes after 3-methylcholanthrene treatment is well established, and is associated with the induction of aryl hydrocarbon hydroxylase (AWH, E.C. 1.14.1.1) activity (Alvares et al., 1967; L u et al., 1973). AHH is of interest since it catalyses the activation of many polycyclic hydrocarbons to their mutagenic metabolites (Huberman et al., 1976; Wood et al., 1976). Because the activity of a number of microsomal mixed-function mono-oxygenase enzymes is increased in diabetic female rats, and the sex-dependent changes in drug-metabolizing enzymes of diabetic rats are similar to changes produced by 3-methylcholanthrene treatment, we have undertaken a series of studies on alterations of A H H activity in diabetic animals, in order to determine whether similar mechanisms may be involved.
Downloaded by [RMIT University Library] at 19:08 21 March 2016
Materials and methods Male and female rats, weighing 160-180 g, of a Sprague-Dawley derived strain (Sasco, Inc., Omaha, Nebr., USA) were individually caged and allowed free access to water and Purina lab chow for at least 5 days before experimental use. The animals were maintained at a temp. of 21 ', with lighting from 0600 h to 1800 h daily. Streptozotocin (STZ) injection of rats (60 mg/kg, Lv.), confirmation of the diabetic state through determination of urinary and blood glucose levels, and treatment of diabetic rats with Protamine Zinc Insulin (PZI, Eli Lilly Co.) were accomplished as previously described (Reinke et al., 1978). Male and female Swiss-Webster mice (Sasco, Inc., Omaha, Nebr., USA) weighing approximately 25 g, were caged in groups of six, and were otherwise submitted to the same environmental conditions as the rats. The mice were given a single injection in the tail vein of 200 mg/kg of STZ, dissolved in 0.05 M citrate buffer, pH 4.5, in a volume of 1.0 ml/lOO g body wt. The S T Z used in these experiments was a generous gift of Dr. William Dulin of the Upjohn Company, Kalamazoo, lVlich., USA. Female rats treated with 3-methylcholanthrene received three daily i.p. injections, 20 mg/kg, dissolved in corn oil. This treatment regimen has previously been reported to maximally induce hepatic microsomal AHH activity in 2-3 days (Stern et al., 1975). To prevent the development of a diabetic state, nicotinamide, 1000 mg/kg, i.p., was administered to female rats 15min before S T Z injection (Dulin & Wyse, 1969; Rerup, 1970; Schein & Loftus, 1968; Schein et al., 1973). Animals which were not treated with PZI were sacrificed by decapitation 7 days after STZ injection. In experiments involving insulin treatment, the animals were sacrificed 10 days after STZ injection, as previously described (Reinke et at., 1978). Washed hepatic microsomes were prepared in 0.15 M KC1-tris buffer (0.05 M tris chloride, p H 7.4, 0.005 M MgC1, and 0.01 M NaC1) by standard centrifugal techniques (Stohs et at., 1971). AHH activity was assayed in 25 ml Erlenmeyer flasks, containing 0.5 pmol NADP', 5 pmol glucose 6-phosphate, and 0.5 units glucose 6-phosphate dehydrogenase (all purchased from Sigma Chemical Co., St. Louis, Mo., USA) and approx. 0.25 mg of microsoma1 protein, in a final volume of 1.0 ml. After a 2 min preincubation at 37", the incubations were initiated by the addition of benzo(a)pyrene, 25 pl of a 6.0 mM soln. in acetone. The reactions were conducted in air in an Eberbach shaker, at 75 cycles/min, exposed to yellow light. After 6 min, the reactions were terminated by the addition of 0.3 ml of triethylamine-Triton X-100 (9 : l), followed by 2-0 ml of aq. 0.05% EDTA soln. AHH activity was determined by the assay procedure of Dehnen et al. (1973) on an AmincoBowman Spectrophotofluorometer. One AHH unit is defined as the formation of 1-0 nmol of product/min/mg microsomal protein, using 3-hydroxybenzo(a)pyrene as the reference standard. The influence of drug metabolism inhibitors on AHH activity was investigated in hepatic microsomes pooled from three or four control or diabetic female rats. Metyrapone (CibaGeigy Corp., Summit, N.J., USA) and S K F 525-A (Smith, Kline and French Co., Philadelphia, Pa., USA) were dissolved in water, while rotenone (Sigma Chemical Co., St. Louis, Mo., USA) and a-naphthoflavone (Aldrich Chemical Co., Inc., Milwaukee, Wisc., USA) were dissolved in acetone. All inhibitors were added to the flasks just before preincubation, and all other conditions were as previously described. Cytochrome P 4 5 0 content was assayed by the method of Omura and Sat0 (1964). Protein analyses (Lowry et at., 1951) were performed on the microsomal suspension used in each assay. All absorption measurements were conducted with a Beckman Acta MVI Spectrophotometer. Statistical analyses utilized Students' t-test.
77 1
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Benxo(a)pyrene Metabolism in Diabetic Rats
Results AHH activity in hepatic microsomes from control and diabetic male and female rats is shown in Table 1. I n diabetic male rats, A H H activity was decreased 70% from control values. I n contrast, AHH activity was increased 75% over control values in the diabetic female rats. Insulin treatment of both male and female diabetic animals returned the altered A H H activities to the corresponding control values. In both diabetic male and female mice, hepatic microsomal AHH activity was increased 65-70% over control values (Table 2), similar to the effect observed in diabetic female rats. Insulin treatment of the diabetic mice was not attempted. T h e time courses for development of hyperglycaemia, increased A H H activity, and cytochrome P-450 content after S T Z administration to female rats are depicted in Table 3. A transient hyperglycaemia was observed 4 h after S T Z injection, but blood glucose levels had fallen by 9 h after injection. A severe hyperglycaemia had developed by 24 h after STZ injection, which persisted throughout the remainder of the study. A H H activity did not increase until 96 h after S T Z injection, and maximal induction was observed 7 days after treatment. Similarly, cytochrome P-450 levels remained unchanged until 48 h after S T Z injection, and were maximally increased at 96 h (Table 3). T h e protective action of nicotinamide on the diabetogenic effects of S T Z is demonstrated in Table 4. Female rats receiving nicotinamide alone did not display any changes in blood glucose levels or hepatic microsomal A H H activity. Animals receiving S T Z alone developed the characteristic hyperglycaemia and Table 1. Effects of streptozotocin-induced diabetes on hepatic microsomal aryl hydrocarbon hydroxylase activity in the rat Aryl hydrocarbon hydroxylase activity (units)
Male rats Female rats
Controls
Diabetic animals
Insulin-treated diabetic animals
0.71 & 0.20 0.34 & 0.03
0.34 & 0.08* 0.59 k 0.06"
0.73 & 0.16t 0.34 k 0.031.
Animals received STZ, 60 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle 10 days before sacrifice. Insulin-treated animals received six daily S.C. doses of PZI, ranging from 12.5 to 20 units/kg, based on urinary glucose levels. Each value is the mean of 4 animals f S.E.M. * P < 0.05 with respect to control animals; t P < 0.05 with respect to diabetic animals.
Table 2. Effects of streptozotocin-induced diabetes on hepatic microsomal aryl hydrocarbon hydroxylase activity in the mouse Aryl hydrocarbon hydroxylase activity (units)
Male mice Female mice
Controls
Diabetic animals
1.63 & 0.06 1.36k0.04
2.75 & 0.29" 2.1 8 k 0.11
*
Animals received STZ, 200 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle 7 days before sacrifice. Each value is the mean for 4 animals S.E.M. * P < 0.05 with respect to control animals.
L. A. Reinke et al.
772
Table 3. Time course of streptozotocin (STZ) effect on blood glucose, hepatic aryl hydrocarbon hydroxylase and cytochrome P-450 in female rats ______
Time (hours)
Downloaded by [RMIT University Library] at 19:08 21 March 2016
~
Blood glucose (mg/lOO ml) Control
0 4 9 24 48 96 168
.___
97+2 110+1 106+2 100k4 97f9 94f9 116+5
STZtreated -
240+12** 147f20 417+15** 439f11** 4 0 7 f 8 ** 445+13**
Aryl hydrocarbon hydroxylase activity (units) Control
0.29 f0.02 0.35 0.05 0.29 f0.01 0.31 f0.04 0.38 & 0.02 0.27 k 0.01 0.33 k 0.03
STZtreated
0.34 2 0.02 0.27 + 0.03 0.24 +- 0.02 0.41 +. 0.06 0.64 0.09" 0.75 + 0.1 1"
-
Cytochrome P-450 content (nmol/mg microsomal protein)
STZtreated
Control
0.62 k 0.03 0.56 k 0.02 0.49 k 0.04 0.67 Ifr 0.03 0.62 k 0.06 0.55 k0.04 0.58 & 0.03
0.57 f0.02 0.42 5 0.01 0.53 f0.03" 0.86 f 0.05" 0.93 k O.lO* 0.95 + 0.03***
Animals sacrificed at 0 were non-fasted and untreated. All other animals received STZ, 60 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle after a 15 h fast, and were immediately fed after injection. Each value is the mean for 3 animals S.E.M. * P < 0.05 with respect to control animals; ** P C 0.001 with respect to control animals; P < 0.005 with respect to control animals.
+
***
Table 4. Effects of streptozotocin-induced diabetes and nicotinamide protection on hepatic microsomal aryl hydrocarbon hydroxylase activity in female rats
Treatment group
I. Control 11. Nicotinamide-treated 111. STZ-treated IV. Nicotinamide and STZ-treated
Blood glucose (mg/100 ml)
106 k 1 97k4 447 k 21 * 123 f 7 t
Aryl hydrocarbon hydroxylase activity (units)
0.21 f0.01 0.18 f0.01 0.36 k 0.03" 0.21 + O.Ol+
The animals received nicotinamide, 1000 mg/kg, or distilled water, 2 ml/kg, i.p. After 15 min, the animals received STZ, 60 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle. The animals were sacrificed 7 days later. Each value is the mean of 4 animals S.E.M. * P
ISSN: 0049-8254 (Print) 1366-5928 (Online) Journal homepage: http://www.tandfonline.com/loi/ixen20
Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from StreptozotocinDiabetic Female Rats L. A. Reinke, S. J. Stohs & H. Rosenberg To cite this article: L. A. Reinke, S. J. Stohs & H. Rosenberg (1978) Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from Streptozotocin-Diabetic Female Rats, Xenobiotica, 8:12, 769-778, DOI: 10.3109/00498257809069590 To link to this article: http://dx.doi.org/10.3109/00498257809069590
Published online: 22 Sep 2008.
Submit your article to this journal
Article views: 2
View related articles
Citing articles: 1 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ixen20 Download by: [RMIT University Library]
Date: 21 March 2016, At: 19:08
XENOBIOTICA,
1979, VOL. 8, NO. 12, 769-778
Increased Aryl Hydrocarbon Hydroxylase Activity in Hepatic Microsomes from Streptozotocin-Diabetic Female Rats L. A. REINKE, S. J. STOHS and H. ROSENBERG Department of Biomedicinal Chemistry, College of Pharmacy, University of Nebraska Medical Center, 42nd and Dewey Avenue, Omaha, Nebraska 68105, U.S.A.
Downloaded by [RMIT University Library] at 19:08 21 March 2016
(Received 13 February 1978; revised 5 September 1978)
1. In streptozotocin-induced diabetic male rats, hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activity was depressed to less than control values, but was increased in microsomes from diabetic female rats. Insulin treatment of diabetic animals returned the altered AHH activity to control values in both sexes of rats. 2. Hepatic microsomal AHH activity was increased over control values in both sexes of diabetic mice.
3. Protection of female rats from the diabetogenic effects of streptozotocin by nicotinamide pretreatment also prevented the increase in AHH activity observed in unprotected animals. 4. Treatment of control and diabetic female rats with S-methylcholanthrene resulted in larger increases in hepatic AHH activity in control animals, but similar increases in cytochrome P-448 content occurred in both treatment groups.
5 . Differential stimulatory or inhibitory effects on AHH activity were observed after the addition of SKF 525-A, metyrapone, and rotenone to hepatic microsomes in vitro from control and diabetic female rats. However, similar stimulatory responses in AHH activity were observed after addition of cc-naphthoflavone to microsomes from both treatment groups.
Introduction We have previously observed a sex-dependent eRect of experimental diabetes on mixed-function mono-oxygenase enzymes in the rat (Reinke et al., 1978). I n streptozotocin (STZ) diabetic male rats, we noted a decrease from control values in hepatic microsomal aminopyrine N-demethylase activity, but an increased aniline hydroxylase activity and cytochrome P-450 content. I n diabetic female rats, aminopyrine N-demethylase activity, aniline hydroxylase activity, biphenyl 4-hydroxylase activity and cytochrome P-450 content were all increased over control values. These observations are consistent with the majority of previous reports involving studies on alloxan-diabetic animals (Dixon et al., 1961, 1963; Kato & Gillette, 1965; Kato & Takahashi, 1969; Kato et al., 1968, 1970 a, b). T h e metabolism of aminopyrine and aniline is thought to be mediated by separate cytochrome P-450 forms (Conney & Kuntzman, 1971 ; Kato et ul., 1969). Therefore, the differential effects of experimental diabetes on these two enzymic activities suggest that the insulin-deficient state may favour the formation of a specific cytochrome form, for example, one favouring aniline hydroxylation. I n addition, Kato has demonstrated that administration of 3-methylcholanthrene to male and female rats produces sex-dependent changes in drug-metabolizing activity which are qualitatively similar to the changes discussed above in experimentally-induced diabetes (Kato et ul., 1969; Kato & Takayanagi, 1968). X.B.
3D
770
L. A. Reinke et al.
T h e formation of cytochrome P-448 in hepatic microsomes after 3-methylcholanthrene treatment is well established, and is associated with the induction of aryl hydrocarbon hydroxylase (AWH, E.C. 1.14.1.1) activity (Alvares et al., 1967; L u et al., 1973). AHH is of interest since it catalyses the activation of many polycyclic hydrocarbons to their mutagenic metabolites (Huberman et al., 1976; Wood et al., 1976). Because the activity of a number of microsomal mixed-function mono-oxygenase enzymes is increased in diabetic female rats, and the sex-dependent changes in drug-metabolizing enzymes of diabetic rats are similar to changes produced by 3-methylcholanthrene treatment, we have undertaken a series of studies on alterations of A H H activity in diabetic animals, in order to determine whether similar mechanisms may be involved.
Downloaded by [RMIT University Library] at 19:08 21 March 2016
Materials and methods Male and female rats, weighing 160-180 g, of a Sprague-Dawley derived strain (Sasco, Inc., Omaha, Nebr., USA) were individually caged and allowed free access to water and Purina lab chow for at least 5 days before experimental use. The animals were maintained at a temp. of 21 ', with lighting from 0600 h to 1800 h daily. Streptozotocin (STZ) injection of rats (60 mg/kg, Lv.), confirmation of the diabetic state through determination of urinary and blood glucose levels, and treatment of diabetic rats with Protamine Zinc Insulin (PZI, Eli Lilly Co.) were accomplished as previously described (Reinke et al., 1978). Male and female Swiss-Webster mice (Sasco, Inc., Omaha, Nebr., USA) weighing approximately 25 g, were caged in groups of six, and were otherwise submitted to the same environmental conditions as the rats. The mice were given a single injection in the tail vein of 200 mg/kg of STZ, dissolved in 0.05 M citrate buffer, pH 4.5, in a volume of 1.0 ml/lOO g body wt. The S T Z used in these experiments was a generous gift of Dr. William Dulin of the Upjohn Company, Kalamazoo, lVlich., USA. Female rats treated with 3-methylcholanthrene received three daily i.p. injections, 20 mg/kg, dissolved in corn oil. This treatment regimen has previously been reported to maximally induce hepatic microsomal AHH activity in 2-3 days (Stern et al., 1975). To prevent the development of a diabetic state, nicotinamide, 1000 mg/kg, i.p., was administered to female rats 15min before S T Z injection (Dulin & Wyse, 1969; Rerup, 1970; Schein & Loftus, 1968; Schein et al., 1973). Animals which were not treated with PZI were sacrificed by decapitation 7 days after STZ injection. In experiments involving insulin treatment, the animals were sacrificed 10 days after STZ injection, as previously described (Reinke et at., 1978). Washed hepatic microsomes were prepared in 0.15 M KC1-tris buffer (0.05 M tris chloride, p H 7.4, 0.005 M MgC1, and 0.01 M NaC1) by standard centrifugal techniques (Stohs et at., 1971). AHH activity was assayed in 25 ml Erlenmeyer flasks, containing 0.5 pmol NADP', 5 pmol glucose 6-phosphate, and 0.5 units glucose 6-phosphate dehydrogenase (all purchased from Sigma Chemical Co., St. Louis, Mo., USA) and approx. 0.25 mg of microsoma1 protein, in a final volume of 1.0 ml. After a 2 min preincubation at 37", the incubations were initiated by the addition of benzo(a)pyrene, 25 pl of a 6.0 mM soln. in acetone. The reactions were conducted in air in an Eberbach shaker, at 75 cycles/min, exposed to yellow light. After 6 min, the reactions were terminated by the addition of 0.3 ml of triethylamine-Triton X-100 (9 : l), followed by 2-0 ml of aq. 0.05% EDTA soln. AHH activity was determined by the assay procedure of Dehnen et al. (1973) on an AmincoBowman Spectrophotofluorometer. One AHH unit is defined as the formation of 1-0 nmol of product/min/mg microsomal protein, using 3-hydroxybenzo(a)pyrene as the reference standard. The influence of drug metabolism inhibitors on AHH activity was investigated in hepatic microsomes pooled from three or four control or diabetic female rats. Metyrapone (CibaGeigy Corp., Summit, N.J., USA) and S K F 525-A (Smith, Kline and French Co., Philadelphia, Pa., USA) were dissolved in water, while rotenone (Sigma Chemical Co., St. Louis, Mo., USA) and a-naphthoflavone (Aldrich Chemical Co., Inc., Milwaukee, Wisc., USA) were dissolved in acetone. All inhibitors were added to the flasks just before preincubation, and all other conditions were as previously described. Cytochrome P 4 5 0 content was assayed by the method of Omura and Sat0 (1964). Protein analyses (Lowry et at., 1951) were performed on the microsomal suspension used in each assay. All absorption measurements were conducted with a Beckman Acta MVI Spectrophotometer. Statistical analyses utilized Students' t-test.
77 1
Downloaded by [RMIT University Library] at 19:08 21 March 2016
Benxo(a)pyrene Metabolism in Diabetic Rats
Results AHH activity in hepatic microsomes from control and diabetic male and female rats is shown in Table 1. I n diabetic male rats, A H H activity was decreased 70% from control values. I n contrast, AHH activity was increased 75% over control values in the diabetic female rats. Insulin treatment of both male and female diabetic animals returned the altered A H H activities to the corresponding control values. In both diabetic male and female mice, hepatic microsomal AHH activity was increased 65-70% over control values (Table 2), similar to the effect observed in diabetic female rats. Insulin treatment of the diabetic mice was not attempted. T h e time courses for development of hyperglycaemia, increased A H H activity, and cytochrome P-450 content after S T Z administration to female rats are depicted in Table 3. A transient hyperglycaemia was observed 4 h after S T Z injection, but blood glucose levels had fallen by 9 h after injection. A severe hyperglycaemia had developed by 24 h after STZ injection, which persisted throughout the remainder of the study. A H H activity did not increase until 96 h after S T Z injection, and maximal induction was observed 7 days after treatment. Similarly, cytochrome P-450 levels remained unchanged until 48 h after S T Z injection, and were maximally increased at 96 h (Table 3). T h e protective action of nicotinamide on the diabetogenic effects of S T Z is demonstrated in Table 4. Female rats receiving nicotinamide alone did not display any changes in blood glucose levels or hepatic microsomal A H H activity. Animals receiving S T Z alone developed the characteristic hyperglycaemia and Table 1. Effects of streptozotocin-induced diabetes on hepatic microsomal aryl hydrocarbon hydroxylase activity in the rat Aryl hydrocarbon hydroxylase activity (units)
Male rats Female rats
Controls
Diabetic animals
Insulin-treated diabetic animals
0.71 & 0.20 0.34 & 0.03
0.34 & 0.08* 0.59 k 0.06"
0.73 & 0.16t 0.34 k 0.031.
Animals received STZ, 60 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle 10 days before sacrifice. Insulin-treated animals received six daily S.C. doses of PZI, ranging from 12.5 to 20 units/kg, based on urinary glucose levels. Each value is the mean of 4 animals f S.E.M. * P < 0.05 with respect to control animals; t P < 0.05 with respect to diabetic animals.
Table 2. Effects of streptozotocin-induced diabetes on hepatic microsomal aryl hydrocarbon hydroxylase activity in the mouse Aryl hydrocarbon hydroxylase activity (units)
Male mice Female mice
Controls
Diabetic animals
1.63 & 0.06 1.36k0.04
2.75 & 0.29" 2.1 8 k 0.11
*
Animals received STZ, 200 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle 7 days before sacrifice. Each value is the mean for 4 animals S.E.M. * P < 0.05 with respect to control animals.
L. A. Reinke et al.
772
Table 3. Time course of streptozotocin (STZ) effect on blood glucose, hepatic aryl hydrocarbon hydroxylase and cytochrome P-450 in female rats ______
Time (hours)
Downloaded by [RMIT University Library] at 19:08 21 March 2016
~
Blood glucose (mg/lOO ml) Control
0 4 9 24 48 96 168
.___
97+2 110+1 106+2 100k4 97f9 94f9 116+5
STZtreated -
240+12** 147f20 417+15** 439f11** 4 0 7 f 8 ** 445+13**
Aryl hydrocarbon hydroxylase activity (units) Control
0.29 f0.02 0.35 0.05 0.29 f0.01 0.31 f0.04 0.38 & 0.02 0.27 k 0.01 0.33 k 0.03
STZtreated
0.34 2 0.02 0.27 + 0.03 0.24 +- 0.02 0.41 +. 0.06 0.64 0.09" 0.75 + 0.1 1"
-
Cytochrome P-450 content (nmol/mg microsomal protein)
STZtreated
Control
0.62 k 0.03 0.56 k 0.02 0.49 k 0.04 0.67 Ifr 0.03 0.62 k 0.06 0.55 k0.04 0.58 & 0.03
0.57 f0.02 0.42 5 0.01 0.53 f0.03" 0.86 f 0.05" 0.93 k O.lO* 0.95 + 0.03***
Animals sacrificed at 0 were non-fasted and untreated. All other animals received STZ, 60 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle after a 15 h fast, and were immediately fed after injection. Each value is the mean for 3 animals S.E.M. * P < 0.05 with respect to control animals; ** P C 0.001 with respect to control animals; P < 0.005 with respect to control animals.
+
***
Table 4. Effects of streptozotocin-induced diabetes and nicotinamide protection on hepatic microsomal aryl hydrocarbon hydroxylase activity in female rats
Treatment group
I. Control 11. Nicotinamide-treated 111. STZ-treated IV. Nicotinamide and STZ-treated
Blood glucose (mg/100 ml)
106 k 1 97k4 447 k 21 * 123 f 7 t
Aryl hydrocarbon hydroxylase activity (units)
0.21 f0.01 0.18 f0.01 0.36 k 0.03" 0.21 + O.Ol+
The animals received nicotinamide, 1000 mg/kg, or distilled water, 2 ml/kg, i.p. After 15 min, the animals received STZ, 60 mg/kg, i.v., or the 0.05 M citrate buffer, p H 4.5, vehicle. The animals were sacrificed 7 days later. Each value is the mean of 4 animals S.E.M. * P
