Metabolism of eicosa-11,14-dienoic acid in rat testes. Evidence for delta8-desaturase activity

The metabolism of [14C]eicosa-11,14-dienoic acid was investigated in rat testes in vivo and in vitro. Intratesticular injection of [1-14C]eicosa-11,14-dienoic acid resulted in the appearance of radioactivity (4-30% of 14C in total fatty acids) in 20-carbon trienoic fatty acids and a small amount (2-3.5%) in arachidonic acid. Analysis of the 20-carbon trienoic acid fraction by ozonolysis indicated that 15 to 34% of the 14C in this fraction was in an 8-carbon fragment originating from eicosa-8,11,14-trienoic acid. The rest (66 to 84%) was in a 5-carbon fragment, presumably originating from eicosa-5,11,14-trienoic acid. Incubation of testicular tissue minces or microsomes with [1-14C]eicosa-11,14-dienoic acid yielded labeled eicosa-8,11,14- and eicosa-5,11,14-trienoic acids in proportions similar to those obtained in vivo. Added unlabeled acetate had no effect on the formation of [14C]eicose-8,11,14-trienoic acid in vitro. Therefore, it is unlikely that the labeled eicosa-8,11,14-trienoic acid arose from elongation of octadeca-6,9,12-trienoic acid with labeled acetate derived from bio-oxidation of the labeled substrate. These results are compatible with a limited desaturation of eicosa-11,14-dienoic acid to eicosa-8,11,14-trienoic acid and provide evidence for delta8 desaturate activity in rat testis.     

Incorporation and metabolism of stearic, oleic, linoleic and alpha-linolenic acids in minimal deviation hepatoma 7288 C cells.

Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled stearic, oleic, linoleic and alpha-linolenic acids. The kinetics of incorporation and conversion to higher homologs was studied. The maximum amounts incorporated in nmoles per mg of cellular protein for stearic, oleic, linoleic and alpha-linolenic acids were 39, 115.6, 90 and 230 respectively. alpha-linolenic acid was converted to octadeca-6,9,12,15-tetraenoic acid (18:1), eicosa-11,14,17-trienoic acid (20:3), eicosa-8,11,14,17 and 5,11,14,17-tetraenoic acids (20:4) and eicosa-5,8,11,14,17-pentaenoic acid (20:5), and also to myristic, palmitic, palmitoleic, stearic and oleic acids. By a mathematical approach, the endogenous pool size of alpha-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, were calculated. Both values decreased when the cells were preincubated with unlabeled alpha-linolenic acid.     

ACTH depresses delta 6 and delta 5 desaturation activity in rat adrenal gland and liver

The in vivo and in vitro effect of ACTH on the biosynthesis of polyunsaturated fatty acid of rat adrenal gland and liver was studied. The administration of ACTH to intact rats produced a significant decrease in the conversion of [1-14C]linoleic acid to gamma-linolenic acid, [1-14C]alpha-linolenic acid to octadeca-6,9,12,15-tetraenoic acid, and [1-14C]eicosa-8,11,14-trienoic acid to arachidonic acid in liver and adrenal microsomes. Isolated adrenocortical cells and hepatocytes obtained from animals treated with ACTH showed a decrease in the incorporation and desaturation of exogenous [1-14C]eicosa-8,11,14-trienoic acid. The addition of ACTH to the incubation medium of adrenocortical cells and hepatocytes isolated from untreated rats also caused a decrease in delta 5 desaturation activity. The effect of ACTH on adrenal and liver desaturases could be produced as a consequence of the release of glucocorticoids, already measured in the experiments. However, the in vitro experiments carried out with hepatocytes isolated from untreated rats, where corticosterone was absent, indicated that ACTH can depress delta 5 desaturation per se.     

The metabolism of (1-14C) stearic acid in rat testicular tissue.

(1) The metabolism of stearic acid was studied in vivo following intratesticular injection of [1-14C] stearate. Soon after injection 14C activity was found mainly in the free fatty acid pool. This was followed at later time periods by transfer of label primarily to the phosphatide pool. During each time period significant amounts of label were recovered at 14CO2. (2) Analysis of 14C-labeled fatty acids from the injected testes demonstrated an initial rapid rate of oxidation and desaturation of [1-14C] stearate followed by a slower steady state rate. It was concluded that the initial rate was due to the rapid turnover of the highly labeled free fatty acid pool followed by a much slower rate as [14C] stearate was esterified to the more metabolically stable phospholipids. Elongation of the labeled stearic or its desaturated derivative was not observed. (3) The rate of desaturation in vitro of stearic acid was measured in microsomal preparations from rat testes and found to be 12.0 +/- 0.5 pmol/min/mg compared to the estimated in vivo value of 22 pmol/min/mg and the value of 390 pmol/min/mg for hepatic microsomal desaturase.     

Polyunsaturated fatty acid biosynthesis from [1-14C]20:3 n-6 acid in rat cultured Sertoli cells. Linoleic acid effect

Primary culture is a suitable system to study lipid metabolism and polyunsaturated fatty acid biosynthesis. Sertoli cell-enriched preparations were used to determine the fatty acid composition after 5 and 7 days in culture (serum free) as well as the uptake and metabolism of [1-14C]eicosa-8,11,14-trienoic acid. The addition of unlabeled linoleic acid (0.2 and 2.0 microg/ml) was also evaluated. Fatty acid methyl esters derived from cellular lipids were analyzed by gas liquid chromatography and radiochromatography. After 5 days in culture, cells had significantly less 18:2, 20:4, 22:5 and 24:5 and more 18:3, 20:3, 22:4 and 24:4 n-6 fatty acids than non-cultured cells. On day 7, an additional increment in 22:4 n-6 and a decrease in linoleic, gamma-linoleic and 24:4 n-6 fatty acids were observed. The presence of linoleic acid (low dose) produced a significant decrease in saturated and monounsaturated acids and an increase in 18:2, 20:4 and 22:5 n-6 fatty acids. At a high concentration almost all fatty acids belonging to 18:2 n-6 increased significantly. The drop in 20:4 n-6/20:3 n-6 ratio was considered as an indirect evidence of a Delta 5 desaturase activity depression. This assumption was corroborated by studying the transformation of [1-14C]eicosa-8,11,14-trienoic acid into 20:4, 22:4, 22:5, 24:4 and 24:5 n-6 fatty acids. We conclude that Sertoli cells after 7 days in culture evidenced changes in the fatty acid profile similar to those described under fat deprivation. The addition of linoleic acid reverted this pattern and indicated that the Delta 5 desaturase activity is a limiting step in the polyunsaturated fatty acid biosynthesis.     

Metabolism of chylomicron arachidonic and linoleic acid in the rat

Chyle and chylomicrons, obtained after feeding thoracic duct cannulated rats [3H]arachidonic (20:4) and [14C]linoleic acid (18:2) in cream, were injected i.v. into recipient animals. 7.5-15 min after injection, the 14C/3H ratio of the triacylglycerols remaining in plasma was about half of that in the injected chylomicrons, indicating that the chylomicron remnants formed retained relatively more [3H]20:4 than [14C]18:2. The 14C/3H ratio of plasma diacylglycerols was about 6-fold lower than that of plasma free fatty acids. The proportion of [3H]20:4 found in plasma cholesteryl esters was several-fold higher than that of [14C]18:2. Inhibition of hepatic lipase by a specific antiserum did not significantly influence the clearance of triacylglycerols, but increased the amount of 3H in plasma diacylglycerols. It also prevented the rapid clearance of phosphatidylethanolamine from plasma. The liver uptake of [3H]20:4 exceeded that of [14C]18:2. Antiserum against hepatic lipase diminished the difference. In contrast, the 14C/3H ratio of adipose tissue was higher than that of the injected chyle lipoproteins.     

Effects of glucagon and dibutyryl adenosine 3', 5'-cyclic monophosphate on oxidative desaturation of fatty acids in the rat.

The present work was undertaken to study the effect of anti-insulinic and glycogenolytic factors on the oxidative desaturation of fatty acids. The effects of glucagon and dibutyryl cyclic AMP on the desaturation of linoleic acid to gamma-linolenic acid, alpha-linolenic acid to octadeca-6,9,12,15-tetraenoic acid, stearic acid to oleic acid, and eicosa-8,11,14-trienoic acid to eicosa-5,8,11,14-tetraenoic acid by rat liver microsomal preparations were investigated. Fasted rats had low desaturating activity, but refeeding a fat-free diet enhanced the activity. Administration of glucagon or dibutyryl cyclic AMP abolished the increase of the 6-desaturase activity elicited by refeeding. However, a similar effect on the 9-desaturase and 5-desaturase activity was not observed. The relationship between these effects and glucose metabolism is discussed.     

Incorporation and metabolism of stearic,oleic, linoleic andα-linolenic acids in Minimal Deviation Hepatoma 7288 C cells

Summary Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled stearic, oleic, linoleic and-linolenic acids. The kinetics of incorporation and conversion to higher homologs was studied. The maximum amounts incorporated in nmoles per mg of cellular protein for stearic, oleic, linoleic and-linolenic acids were 39, 115.6, 90 and 230 respectively.-linolenic acid was converted to octadeca-6,9,12,15-tetraenoic acid (18:4), eicosa-11,14,17-trienoic acid (20:3), eicosa-8,11,14,17 and 5,11,14,17-tetraenoic acids (20:4) and eicosa-5,8,11,14,17-pentaenoic acid (20:5), and also to myristic, palmitic, palmitoleic, stearic and oleic acids. By a mathematical approach, the endogenous pool size of-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, and the capacity of the cell to convert-linolenic acid to eicosa-5,8,11,14,17-pentaenoic acid, were calculated. Both values decreased when the cells were preincubated with unlabeled-linolenic acid.Dedicated to ProfessorLuis F. Leloir on the occasion of his 70th birthday.     

Metabolism of unique diarachidonoyl and linoleoylarachidonoyl species of ethanolamine and choline phosphoglycerides in rat testes

Selected molecular species of rat testicular 1,2-diradyl-sn-glycero-3-phosphocholines and 1,2-diradyl-sn-glycero-3-phosphoethanolamines were quantitated as their diradylglycerobenzoate derivatives, using a recently developed high-performance liquid chromatographic method. Increased amounts of docosapentaenoic acid were found in glycerophospholipids containing ether moieties compared with the diacyl phospholipids (e.g., docosapentaenoate-containing species comprised more than 80% of the alkylacyl subclass of the ethanolamine phosholipids as opposed to 29.3% of the diacyl subclass). Within 2 h after intratesticular injections of [5,6,8,9,11,12,14,15-3H]arachidonic acid, the 20:4-20:4 and 18:2-20:4 molecular species of the diacyl subclass of both the choline and ethanolamine glycerophosphatides had the highest specific radioactivities. These unique molecular species (20:4-20:4 and 18:2-20:4) also exhibited the largest percentage decrease in specific radioactivity 24 h after the intratesticular injections of [3H]arachidonic acid, which indicates these two species possess a high metabolic turnover. Two of the arachidonate-containing molecular species (18:1-20:4 and 18:0-20:4) in the ethanolamine plasmalogens showed only a small decrease in specific radioactivity, whereas a third species (16:0-20:4) actually had a 44% increase in specific radioactivity 24 h after the intratesticular injections of [3H]arachidonate. These data indicate that the 20:4-20:4, 18:2-20:4 and 18:1-20:4 species of phosphatidylcholine and/or phosphatidylethanolamine are most rapidly labeled after administration of [3H]arachidonic acid and that they appear to serve as the source of the [3H]arachidonate that is ultimately transferred to ethanolamine plasmalogens.     

Evidence for peroxisomal retroconversion of adrenic acid (22:4(n-6)) and docosahexaenoic acids (22:6(n-3)) in isolated liver cells

The intracellular localization of the oxidation of [2-14C]adrenic acid (22:4(n-6)) and [1-14C]docosahexaenoic acid (22:6(n-3)) was studied in isolated liver cells. The oxidation of 22:4(n-6) was 2-3-times more rapid than the oxidation of 22:6(n-3), [1-14C]arachidonic acid (20:4(n-6)) or [1-14C]oleic acid (18:1). (+)-Decanoylcarnitine and lactate, both known to inhibit mitochondrial beta-oxidation, reduced the oxidation of 18:1 distinctly more efficiently than with 22:4(n-6) and 22:6(n-3). In liver cells from rats fed a diet containing partially hydrogenated fish oil, the oxidation of 22:6(n-6) and 22:6(n-3) was increased by 30-40% compared with cells from rats fed a standard pellet diet. With 18:1 as substrate, the amount of fatty acid oxidized was very similar in cells from animals fed standard pellets or partially hydrogenated fish oil. Shortened fatty acids were not produced from [5,6,8,9,11,12,14,15-3H]arachidonic acid. In hepatocytes from rats starved and refed 20% fructose, a large fraction of 14C from 22:4 was recovered in 14C-labelled C14-C18 fatty acids. Oxidation of 22:4 thus caused a high specific activity of the extramitochondrial pool of acetyl-CoA. The results suggest that 22:4(n-6) and to some extent 22:6(n-3) are oxidized by peroxisomal beta-oxidation and by this are retroconverted to arachidonic acid and eicosapentaenoic acid.     

Biosynthesis of polyunsaturated fatty acids by the australian field cricket,Teleogryllus commodus

Aspects of testicular fatty acid biochemistry from the Australian field cricket, Teleogryllus commodus, are reported. Over 10% of the phospholipid fatty acids were C20 polyunsaturated fatty acids (PUFAs), with nearly 6% arachidonic acid (20:4). The testes and ovaries accumulated a large proportion of label from radioactive arachidonic acid that was injected into the hemocoel (about 30%). Specificity in the uptake was shown by comparison to a similar study with labelled stearic acid, in which only 1.5% of the radioactivity was taken up by testes. Sixty percent of the radioactivity taken up by testes from [³H]20:4 was incorporated into phospholipids and 30% into triacylglycerols. Fat body of males and females incorporated 27% of the [³H]20:4 into phospholipids and 68% (males) or 55% (females) into triacylglcyerols. Radioactivity from [1-¹⁴C]acetate was incorporated into testicular linoleic acid and eicosatrienoic acid, but not eicosatetraenoic acid, suggesting the de novo biosynthesis of both 18:2 and a C20 PUFA by this species. Label from injected [U-¹⁴C]linoleic acid was recovered mostly as linoleic acid, with a small portion of the recovered radioactivity in eicosatrienoic acid, but not eicosatetraenoic acid. Very little label from injected linoleic acid occurred as monounsaturated or saturated fatty acids, indicating only slight, if any, β-oxidation of 18:2 to acetate and subsequent lipid synthesis.     

In vitro and in vivo synthesis of long-chain fatty acids from (1-14C) acetate in the renal papillae of rats.

1. The relationship between the rate of [1-14C] acetate incorporation into the fatty acids of renal papillary lipids and the acetate concentration in the medium has been measured. 2. [1-14C] acetate was incorporated mainly into fatty acids of phospholipids and triacylglycerols. Only a few per cent of the radioactivity was found in the free fatty acid fraction. 3. The major part of the [1-14C] acetate was found to be incorporated by a chain elongation of prevalent fatty acids. The major component of the poly-unsaturated fatty acids in triacylglycerols and the major product of fatty acid synthesis from [1-14C] acetate in vitro was demonstrated by mass spectrometry to be docosa-7,10,13,16-tetraenoic acid. 4. The radioactivity of docosa-7,10,13,16-tetraenoic acid accounted for 40% of total radioactivity in triacylglycerol fatty acids (lipid droplet fraction) and 20% of total radioactivity in membrane phospholipid fatty acids.     

The metabolism of glucose in diaphragm muscle from normal rats, from streptozotocin-treated diabetic rats and from rats treated with anti-insulin serum

1. The metabolism of [U-¹⁴C]glucose by the isolated diaphragm muscle of normal rats, rats rendered diabetic with streptozotocin and rats with transitory insulin deficiency after an injection of anti-insulin serum was studied. 2. The incorporation of [¹⁴C]glucose into glycogen and oligosaccharides was significantly decreased in the diabetic diaphragm muscle and in the muscle from rats treated with anti-insulin serum. 3. Neither diabetes nor transitory insulin deficiency influenced the oxidation of glucose, or the formation of lactate and hexose phosphate esters from glucose. 4. Insulin fully restored the incorporation of glucose into glycogen and maltotetraose in the diabetic muscle, but the incorporation into oligosaccharides, although increased in the presence of insulin, was significantly lower than the values obtained with normal diaphragm in the presence of insulin.     

Age‐Related Changes in Fatty Acids in Obese Offspring of Streptozotocin‐Induced Diabetic Rats

Objective: The long‐term effects of fetal hyperinsulinemia, time course of changes in liver and very‐low‐density lipoprotein (VLDL) lipid levels and fatty acid compositions were investigated in obese offspring of streptozotocin‐induced mildly diabetic rats. Research Methods and Procedures: Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on day 5 of gestation. Control pregnant rats were injected with citrate buffer. Liver and VLDL lipids and fatty acids were analyzed in offspring at different ages. Results: At birth, obese pups had higher VLDL triglyceride levels, saturated fatty acids, and C20:4n‐6. They also had lower C18:2n‐6 proportions in VLDL triglycerides, phospholipids, and cholesteryl esters than controls pups. In 1‐month‐old male and female obese rats, VLDL and liver lipid amounts were similar to those in their respective controls; however, high levels of C18:2n‐6 and C20:4n‐6 were noted in liver and VLDL lipids. At the age of 2 months, liver and VLDL triglyceride levels were higher in obese females than in control females. Fatty acid abnormalities seen in obese rats included low C18:3n‐3 and high C22:6n‐3 proportions in liver triglycerides and phospholipids. At the age of 3 months, obese rats, both males and females, compared with control animals, had higher VLDL and hepatic lipids with reduced C20:4n‐6 levels and polyunsaturated/saturated fatty acids ratios in hepatic and VLDL triglycerides and phospholipids. Discussion: Fetal obesity, associated with alterations in VLDL lipid fatty acid composition, represents an important risk factor for adult obesity and diabetes.     

Effects of fenofibrate and insulin on the biosynthesis of unsaturated fatty acids in streptozotocin diabetic rats

Both insulin and PPAR-alpha up-modulate hepatic Delta9, Delta6 and Delta5 desaturating enzymes involved in the biosynthesis of mono- and polyunsaturated fatty acids. Currently, we have examined for 9 days the independent and simultaneous effects of daily glargine insulin and fenofibrate administration on the insulinemia, glycemia, hepatic acyl-CoA oxidase activity and mRNAs and enzymatic activities of stearoyl-CoA desaturase-1 (SCD-1) and Delta5 desaturase in streptozotocin diabetic rats. Glargine insulin depressed the hyperglycemia of diabetic rats at 4h, but not after 24h of injection. Fenofibrate increased the radioimmunoreactive insulinemia in non-diabetic rats without changing the glycemia. Insulin increased the mRNAs and activities of SCD-1 and Delta5 desaturase depressed in diabetic rats. Fenofibrate increased acyl-CoA oxidase activity, and the mRNAs and activities of both desaturating enzymes in non-diabetic, diabetic and insulin-treated diabetic rats, but was less effective in the mRNAs modification of diabetic animals. Therefore, insulin, and fenofibrate through PPAR-alpha activation, enhance liver mRNAs and activities of SCD-1 and Delta5 desaturases independently and synergistically through different mechanisms. Insulin and fenofibrate independently increased the 18:1/18:0 ratio in liver lipids, increasing the fluidity of the membranes. The 20:4/18:2 ratio was maintained. Fenofibrate increased palmitic acid, but decreased stearic acid percentage in liver lipids.     

Oxidative desaturation of eicosa-8,11-dienoic acid to eicosa-5,8,11-trienoic acid: comparison of different diets on oxidative desaturation at the 5,6 and 6,7 positions

The oxidative desaturation of [1-(14)C]eicosa-8,11-dienoic acid to eicosa-5,8,11-trienoic acid by rat liver microsomes was studied, and the kinetic conditions appropriate to measure the specific activity of the enzyme were determined. A comparative study of the effects of a balanced diet and essential fatty acid-free diets on the oxidative desaturation of oleic and linoleic acids at the 6,7 position and the oxidative desaturation of eicosadienoic acid at the 5,6 position were made. Eicosadienoic acid showed a higher conversion than oleic acid for all the diets. The conversion of oleic and linoleic acids to Delta6 acids was equally increased by fat-free diets with or without added methyl palmitate, whereas the oxidative 5-desaturation of eicosadienoic acid at the 5,6 position was not changed. The effect was apparently independent of the amount of endogenous free fatty acids. The results suggest that the rate-limiting and principal regulatory step in the biosynthesis of eicosa-5,8,11-trienoic acid is the 6-desaturation of oleic acid. The 5-desaturation of eicosadienoic acid was increased by a protein diet and decreased by alloxan diabetes to a lesser extent than the 6-desaturation of linoleic acid. The 5-desaturation of eicosadienoic acid would constitute a secondary regulatory step.     

The effect of feeding rats with partially hydrogenated marine oil or rapeseed oil on the chain shortening of erucic acid in perfused heart.

1. The metabolism of [14(-14)C]erucic acid and [U-14C]palmitic acid was studied in perfused hearts from rats fed diets containing hydrogenated marine oil, rapeseed oil or peanut oil for three weeks. 2. [14C]Erucic acid was shortened to [14C]eicosenoic acid (20 : 1, n -- 9) and [14C]oleic acid (18 : 1, n -- 9) in perfused rat hearts from all diet groups. The rapeseed oil diet caused a three-fold increase and the marine oil diet a four-fold increase in the amount of chain-shortened products recovered in heart lipids at the end of perfusion, compared to peanut oil diet. 3. The content of C16:1, C18:1 and C20:1 fatty acids was increased in heart lipids of rats fed hydrogenated marine oil or rapseed oil diet, compared to peanut oil diet. 4. Feeding hydrogenated marine oil or rapeseed oil to the rats induced a 85% increase in catalase activity, a 20% increase in the activity of cytochrome oxidase and a 30--40% increase in the content of total CoA in the heart compared to rats fed peanut oil diet. 5. It is suggested that [14(-14)C]erucic acid is shortened by the beta-oxidation system of peroxisomes in the heart. The increased chain shortening in the hearts from animals fed rapeseed oil or partially hydrogenated marine oil for three weeks may be an important part of an adaptation process.     

Mitochondrial and peroxisomal oxidation of arachidonic and eicosapentaenoic acid studied in isolated liver cells

The partitioning between peroxisomal and mitochondrial beta-oxidation of [1-14C]eicosapentaenoic acid (20:5(n-3] and [1-14C]arachidonic acid (20:4(n-6)) was studied. In hepatocytes from fasted rats approximately 70% of the fatty acid substrate was oxidized with oleic, linoleic, eicosapentaenoic and docosahexaenoic (22:6(n-3)) acid, even more with adrenic (22:4(n-6)) and less with arachidonic acid. When the mitochondrial oxidation was suppressed by fructose refeeding and by (+)-decanoylcarnitine, the fatty acid oxidation in per cent of that in cells from fasted rats was with 18:1(n-9) 7%, 18:2(n-6) 8%, 20:4(n-6) 12%, 20:5(n-3) 20%, 22:4(n-6) 57% and for 22:6(n-3) 29%. The fraction of 14C recovered in palmitate and other newly synthesized fatty acids after fructose refeeding decreased in the order 22:4(n-6) greater than 22:6(n-3) greater than 20:5(n-3) greater than 20:4(n-6) and was very small with 18:1(n-9) and 18:2(n-6). In cells from both fed and fructose-refed animals 20:5(n-3) was efficiently elongated to 22:5(n-3) and 22:6(n-3). 20:5(n-3) and 20:4(n-6) were not elongated after fasting. The phospholipid incorporation with [1-14C]20:5(n-3) decreased during prolonged incubations while it remained stable with [1-14C]arachidonic acid. The results suggest that peroxisomes contribute more to the oxidation of 20:5(n-3) than with 20:4(n-6) although both substrates are probably oxidized mainly in the mitochondria.     

Enhanced testicular antioxidant capacity in streptozotocin-induced diabetic rats: protective role of vitamins C and E and selenium

Diabetes mellitus is associated with diabetic impairment of testicular function, ultimately leading to reduced fertility. Its etiology may involve oxidative damage by reactive oxygen substances, and protection against this damage can be offered by antioxidant supplementation. The aim of this study was to investigate the effects of intraperitoneal administration of vitamin C and E, selenium (Se), and vitamin E plus Se (COM) on concentrations of lipid peroxide (as malondialdehyde; MDA), reduced glutathione (GSH), and vitamin E concentrations and glutathione peroxidase (GSH-Px) activity in the testes of rats with diabetes induced by streptozotocin (STZ). Sixty groups were used (10 animals each) and these animals were initially allocated to two groups: control group and diabetic group. The diabetic group was subdivided into five groups as follows: diabetic control (DC), vitamin E, Se, COM, and vitamin C. Animals in the DC group and vitamin C, vitamin E, Se, and COM groups were made diabetic by the injection of STZ on 4 d after an injection of vitamins C and E, Se, and COM. Those vitamins and Se were also administered for 21 consecutive days. The MDA, vitamin E, GSH levels, and GSH-Px activities in testes were determined. Although the vitamin E concentration was higher in the control than in the DC group, the MDA levels were found to be lower in the control than in the DC group. The MDA levels in the testes samples of vitamin C, vitamin E, Se, and COM groups were lower than the DC group. However, GSH-Px activity and GSH levels in the testes were not significantly different between the control and DC groups. Vitamin E concentrations in the vitamin C, vitamin E, Se, and COM groups and GSH levels and GSH-Px activities in the Se, COM, and vitamin C groups were higher than either the control or DC group. The results indicate that reactive oxygen substances may be involved in possible testicular complications in diabetes of rats. Administration of vitamins C and E and Se reduced the testicular lipid peroxidation; these vitamins and Se had significant protective effects on testes of rats against oxidative damage in diabetes.     

Effect of streptozotocin diabetes on the pituitary-testicular axis in the rat

The pituitary-testicular axis was investigated in the streptozotocin diabetic male rat to determine the relationship between hormonal alterations and steroidogenic activity. Male Sprague-Dawley rats weighing 250-300 g were used in all experiments. Diabetes was induced by intraperitoneal injection (40 mg/kg body wt.) of streptozotocin and they were studied with non-diabetic controls. The observations on these animals were compared to those from diabetic rats treated with 1-5 IU protamine zinc insulin. Steroidogenic activity was determined by measuring the per cent of [4-14C]-cholesterol converted to [4-14C]-pregnenolone and [4-14C]-progesterone. Plasma concentrations of LH, FSH and prolactin were measured by RIA. Streptozotocin induced diabetes resulted in significantly reduced plasma LH (34%, p less than 0.20) and prolactin (53%, p less than 0.001) but did not modify FSH concentrations. Insulin treatment completely and partially restored abnormal LH and prolactin release. The activity of the enzyme cleaving the side-chain of cholesterol (rate limiting step in steroidogenesis) was considerably reduced in the diabetic state (59%, p less than 0.002) and insulin treatment restored it to even supranormal levels (not significant). Our findings suggest that insulin may play a physiological and differential role in regulating the secretory activity of the anterior pituitary. The insulin is needed for normal LH and prolactin release and Leydig cells function but its role in FSH release and Sertoli cells function is not clear.