Originals Basic Sensitivity and Responsiveness of Glucose Output to Insulin in Isolated Perfused Liver from Dexamethasone-Treated Rats
Summary To elucidate insulin action on hepatic glucose output (glycogenolysis) in the state exposed to an excess glucocorticoid, the fed rat liver was isolated and cyclically perfused with a medium containing 5 mM glucose and various concentrations of insulin. The rat was subcutaneously injected with 1 mg/kg of dexamethasone (Dex) for 7 days. Dex-treated rats showed marked increases of serum insulin and plasma glucose level compared with those in control rats. Hepatic glycogen contents in Dex group were markedly increased compared with those in control (115 ± 5 and 28 + 4 mg/g, respectively). Insulin extraction rate in the perfused liver was not different between control and Dex group. Perfusate glucose level after 60 min perfusion was much higher in the Dex-treated rat liver than that of the control at 0 nU/ml insulin (34.5 ±2.5 vs 23.0 + 2.0 mM, P < 0.01), and reduced to the nadir level (19.0 + 3.0 and 13.0+ 1.5 mM, respectively) at 100 uU/ml insulin in both groups, i. e., the decreasing rate in perfusate glucose level was not different between Dex and control group (43 % and 44%, respectively).
crease hepatic glycogen deposition, and glycogenolysis in the liver has an important role to supply glucose to the circulation for a short fasting period (Shikama, Yajima and Ui 1980). The effects of insulin on supply of glucose from liver glycogen in the glucocorticoid-treated animal are not fully clear. In the present study, the liver of dexamethasone(Dex)-treated rats was isolated and perfused to examine sensitivity and responsiveness of the hepatic glucose output to insulin. Materials and Methods Male Wistar rats weighing 140 g were used throughout this study. The animals were divided into two groups. Dextreated rats were prepared by subcutaneous injection of dexamethasone 1 mg/kg (Merck & Co., NJ, USA) given every day at 18:00 for 7 days, and control rats were prepared by the injection of saline. The rat was housed under standard lights on 5:00—19:00, and maintained on standard chow. Rats, fed ad libitum, were anesthetized at 12:00— 15:00 with pentobarbital sodium and provided to the following studies. Glucose Tolerance
Glucose 0.5 g/kg was intravenously injected from the right femoral vein and blood samplings were carried out at 0,10,20 min from the left femoral vein. Liver
These results suggest that Dex-treatment augments hepatic glucose output, but does not affect the sensitivity and responsiveness of that to insulin. Key words Dexamethasone — Insulin — Liver Glycogen
Introduction Although several studies demonstrate that glucocorticoid treatment reduced glucose utilization and induced hyperinsulinemia, it is still controversial whether glucocorticoid treatment diminishes insulin action on the hepatic glucose production (Riddick, Reisler and Kipnis 1962; Shamoon, Soman and Sherwin 1980; Shamoon, Hendler and Sherwin 1980; Rizza, Mandarino and Gerich 1982; Pagano, CavalloPerin, Cassader, Bruno, Ozzello, Masciola, Dallomo and Imbimbo 1983). One of main effects of glucocorticoid is to inHorm.metab.Res.23(1991)53-55 © GeorgThiemeVerlag Stuttgart-New York
Test
Perfusion
According to the method of Misbin, Merimee and Lowenstein (1976), the liver was isolated and cyclically perfused with a medium consisting of 118 mM NaCl, 3.5 mM KC1, 1.2 mM MgSO4, 1.2 mM KH2PO4, 2.5 mM CaCh, 15.5 mM NaHCO3, 8.0 mM HEPES-NaOH (pH 7.4), 5 mM glucose and 3 % bovine serum albumin (fraction V, Sigma, St. Louis, USA), equilibrated with 95 % O2 + 5% CO2 gas using a moniliform glass oxygenator. After a washout perfusion for 10 min, 30 ml of perfusate was recirculated at aflowrate of 20 ml/min for 60 min. Porcine insulin (Novo, Denmark) was added to perfusate to maintain 100-40% of the concentration at start throughout the experiment (Fig. 2). Glycogen
Content
Liver glycogen was extracted with trichloroacetate solution and precipitated with ethanol (Stetten, Katzen and Stetten 1956). The precipitation was desicated and weighed. Plasma and perfusate glucose was determined by glucose oxidase method. Serum and perfusate insulin was assayed by a radioimmunoassay system using an anti-porcine insulin serum and porcine insulin for the standard. Student's t-test was used for statistics. Received: 30 May 1989
Accepted: 3 July 1990
Downloaded by: Universite de Sherbrooke. Copyrighted material.
O. Mokuda , Y. Sakamoto , T. Ikeda and H. Mashiba Third Department of Internal Medicine, Teikyo University School of Medicine, Chiba First Department of Internal Medicine, Tottori University School of Medicine, Yonago, Japan
Horm. metab. Res. 23 (1991)
Fig. 1 Intravenous glucose tolerance test. Control amethasone-treated (O) (mean + SD, n = 5).
O. Mokuda, Y. Sakamoto, T. Ikeda and H. Mashiba
• ); dex-
Fig. 2 Insulin extraction by liver of control ( • ) and dexamethasone-treated (O) rats. Insulin extraction rate was not different between control and dexamethasone-treated, and almost constant in a range of 20-500 (ill/ml (upper panel) and throughout perfusion period for 60 min at 500 uU/ml (lower panel) (mean±SD, n = 5).
Results Body weight of the Dex-treated rat was significantly smaller than the control rat (148 ± 15 g vs 173 + 6 g, P < 0.05). Liver weight was almost similar between Dex and control group (8.7 + 0.5 g and 9.1 + 0.7 g). Glycogen content in the liver was markedly increased in Dex group compared with that in control (115 ± 5 mg/g wet tissue vs 28 + 4 mg/g, P < 0.01). In glucose tolerance test, Dex-treated rats showed significant increases of plasma glucose and serum insulin level at each time compared with control rats (Fig. 1). As shown in Fig. 2, the liver of Dex-treated rats removed insulin from the perfusate to the same degree as that of control rats. Insulin extraction rate of the perfused liver was almost constant in a range of 20—500 mU/ml insulin concentration, and showed no remarkable changes for 60 min. According to this insulin clearance rate, supplement insulin was, every 15 min, added to the perfusate to maintain 100—40% of insulin level at the start of experiment. Effect of insulin on perfusate glucose is shown in Fig. 3. Perfusate glucose in the experiment of control rat liver was 23 + 2.0 mM without insulin and declined to reach the nadir level of 13 + 1.5 mM by the addition of 100 uU/ml insulin. In Dex-treated rat livers, perfusate glucose was 34.5 + 2.5 mM without insulin and reached the nadir level of 19 ± 3 mM at 100 u,U/ml insulin. The decrement in perfusate glucose in response to 100 uU/ml insulin was 10 m M (44% of the basal) in control and 15.5 mM (43 %) in Dex-treated. Discussion As commonly known, dexamethasone administration induced marked hyperglycemia and hyperinsulinemia in rats. Chap, Jones, Chou, Hartley, Entman and Field
Fig. 3 Effect of insulin on perfusate glucose (hepatic glucose output). Insulin concentration is the value at start of perfusion (mean + SD, n = 5).
(1986) noted in the study using conscious dogs that a decrease of hepatic insulin extraction contributed to hyperinsulinemia caused by dexamethasone treatment. Cam and Amatruda (1982) reported that insulin degradation was enhanced in hepatocytes from dexamethasone-treated rat. This study demonstrated that insulin extraction rate in Dex-treated rat liver was not changed. But we did not measure the effects of portal blood flow on insulin extraction rate in-vivo.
Downloaded by: Universite de Sherbrooke. Copyrighted material.
54
Horm. metab. Res. 23 (1991)
Treatment
Previous studies showed that glucocorticoids reduced the peripheral glucose utilization (Riddick, Reisler and Kipnis 1962; Shamoon, Soman and Sherwin 1980; Shamoon, Hendler and Sherwin 1980; Rizza, Mandarino and Gerich 1982; Pagano, Cavallo-Perin, Cassader, Bruno, Ozzello, Masciala, Dallomo and Imbimbo 1983), and some investigators concluded that glucocorticoids induced an insulin resistant state due to the inhibition of glucose transport system in peripheral tissue {Olefsky 1975; Nelson and Murray 1987). On the other hand, effects of glucocorticoids on the hepatic glucose output have not been sufficiently established. We obtained the finding that, in perfusion system, the sensitivity and responsiveness of the hepatic glucose output to insulin were not affected by dexamethasone treatment. Some in-vivo studies showed that glucocorticoids increased hepatic glucose output and decreased the insulin sensitivity in liver (Rizza, Mandarino and Gerich 1982; Chap et al. 1986), and other studies resulted in no significant influence on the hepatic glucose production (Shamoon, Soman and Sherwin 1980; Eigler, Sacca and Sherwin 1979; Pagano et al. 1983). The in-vitro studies, using cultured rat hepatocytes, showed that dexamethasone increased both the sensitivity and responsiveness of glycogen synthesis to insulin (Fleig, Nother-Fleig, Steudter, Enderle and Ditschuneit 1985) and inversely decreased both the sensitivity and responsiveness of aminoisobutyrate uptake to insulin (Cam and Amatruda 1982), or increased the responsiveness of lipogenesis to insulin but decreased the sensitivity of that (Amatruda, Danahy and Chang 1983). Hepatic glycogen deposition is accelerated by glucocorticoids together with the simultaneous elevation of portal venous glucose and insulin level (Shikama, Yajima and Ui 1980). Moreover, glucocorticoids increase the circulating glucagon, amino acids, and free fatty acids giving some influences on hepatic glucose metabolism (Marco, Calle, Roman, Diaz-Fierros, ViUanueva and Valverde 1973; Wise, Hendler and Felig 1973; Venkatesan, Davidson and Hutchinson 1987). Therefore the confliction of these results is thought to be caused by differences of methods, i. e., fed/fasted, in-vivo/in-vitro, cultured hepatocytes/perfused liver, in-vitro treatment/in-vivo administration of glucocorticoid and durations of administration (Ninomiya, Forbath and Hetenyi 1965; Venkatesan, Davidson and Hutchinson 1987). In our preliminary study, after an overnight fasting the rat liver glycogen content was extremely exhausted (6 + 2 mg/g) and the basal hepatic glucose output was negligible, i. e., perfusate glucose was 4.9 + 0.9 mM without insulin in the same experiment. Therefore, it was thought that this experiment was designed to observe mainly hepatic glycogenolysis and to omit humoral factors. In the Dex-treated rat liver, the acceleration of basal glucose output seemed to be related to perfuse the glycogen-rich liver with a medium containing 5 mM glucose. In further studies, it is required to correct the perfusate glucose concentration to the basal plasma glucose level.
Caw, J. F., J. M. Amatruda: Glucocorticoid-induced insulin resistance. The importance of postbinding events in the regulation of insulin binding, action, and degradation in freshly isolated and primary cultures of rat hepatocytes. J. Clin. Invest. 69: 866-875 (1982) Chap, Z., R. H. Jones, J. Chou, C. J. Hartley, M. L. Entman, J. B. Field: Effect of dexamethasone on hepatic glucose and insulin metabolism after oral glucose in conscious dogs. J. Clin. Invest. 78:1355— 1361 (1986) Eigler, N, L. Sacca, R. S. Sherwin: Synergistic interactions of physiologic increments of glucagon, epinephrine, and Cortisol in the dog. J. Clin. Invest. 63:114-123 (1979) Fleig, W. E., G. Nother-Fleig, S. Steudter, D. Enderle, H. Ditschuneit: Regulation of insulin binding and glycogenesis by insulin and dexamethasone in cultured rat hepatocytes. Biochim. Biophys. Acta 847:352-361(1985) Marco, J., C. Calle, D. Roman, M. Diaz-Fierros, M. L. ViUanueva, I. Valverde: Hyperglucagonism induced by glucocorticoid treatmentinman.NewEngl.J.Med.288:128-131 (1973) Misbin, R. I., T. J. Merimee, J. M. Lowenstein: Insulin removal by isolated perfused rat liver. Am. J. Physiol. 230:171 -177 (1976) Nelson, D. H., D. K. Murray: Dexamethasone inhibition of hydrogen peroxide-stimulated glucose transport. Endocrinology 120: 156— 159(1987) Ninomiya, R., N. F. Forbath, G. Hetenyi: Effect of adrenal steroids on glucose kinetics in normal and diabetic dogs. Diabetes 14: 729— 739(1965) Olefsky, J. M.: Effect of dexamethasone on insulin binding, glucose transport, and glucose oxidation of isolated rat adipocytes. J. Clin. Invest. 56:1499-1508(1975) Pagano, G., P. Cavallo-Perin, M. Cassader, A. Bruno, A. Ozzello, P. Masciola, A. M. Dallomo, B. Imbimbo: An in vivo and in vitro study of the mechanism of prednisone-induced insulin resistance in healthy subjects. J. Clin. Invest. 72:1814-1820 (1983) Riddick, F. A., D. M. Reisler, D. M. Kipnis: The sugar transport system in striated muscle: Effect of growth hormone, hydrocortisone and alloxan diabetes. Diabetes 11: 171-178(1962) Rizza, R. A., L. J. Mandarino, J. E. Gerich: Cortisol-induced insulin resistance in man: Impaired suppression of glucose production and stimulation of glucose utilization due to a postreceptor defect of insulin action. J. Clin. Endocrinol. Metab. 54:131-138(1982) Shamoon, H., R. Hendler, R. S. Sherwin: Altered responsiveness to Cortisol, epinephrine, and glucagon in insulin-infused juvenileonset diabetics. Diabetes 29:284-291 (1980) Shamoon, H, V. Soman, R. S. Sherwin: The influence of acute physiological increments of Cortisol on fuel metabolism and insulin binding to monocytes in normal humans. J. Clin. Endocrinol. Metab. 50:495-501(1980) Shikama, H, M. Yajima, M. Ui: Glycogen metabolism in rat liver during transition from the fed to fasted states. Biochim. Biophys. Acta631:278-288(1980) Stetten, M. R., H. M. Katzen, D. Stetten: Metabolic inhomogeneity of glycogen as a function of molecular weight. J. Biol. Chem. 222: 587-599(1956) Venkatesan, N, M. B. Davidson, A. Hutchinson: Possible role for the glucose-fatty acid cycle in dexamethasone-induced insulin antagonism in rats. Metabolism36:883-891 (1987) Wise, J. K., R. Hendler, P. Felig: Influence of glucocorticoids on glucagon secretion and plasma amino acid concentrations in man. J. Clin. Invest. 52:2774-2782 (1973) Requests for reprints should be addressed to:
O. Mokuda 3rd Dept. of Internal Medicine Teikyo University Amatruda, J. M., S. A. Danahy, C. L. Chang:Thz effects of glucocortiIchihara-City coids on insulin-stimulated lipogenesis in primary cultures of rat Chiba 299-01 (lapan) hepatocytes. Biochem. J. 212:135-141 (1983) References
55
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Hepatic Glucose Output in Dexamethasone
Summary To elucidate insulin action on hepatic glucose output (glycogenolysis) in the state exposed to an excess glucocorticoid, the fed rat liver was isolated and cyclically perfused with a medium containing 5 mM glucose and various concentrations of insulin. The rat was subcutaneously injected with 1 mg/kg of dexamethasone (Dex) for 7 days. Dex-treated rats showed marked increases of serum insulin and plasma glucose level compared with those in control rats. Hepatic glycogen contents in Dex group were markedly increased compared with those in control (115 ± 5 and 28 + 4 mg/g, respectively). Insulin extraction rate in the perfused liver was not different between control and Dex group. Perfusate glucose level after 60 min perfusion was much higher in the Dex-treated rat liver than that of the control at 0 nU/ml insulin (34.5 ±2.5 vs 23.0 + 2.0 mM, P < 0.01), and reduced to the nadir level (19.0 + 3.0 and 13.0+ 1.5 mM, respectively) at 100 uU/ml insulin in both groups, i. e., the decreasing rate in perfusate glucose level was not different between Dex and control group (43 % and 44%, respectively).
crease hepatic glycogen deposition, and glycogenolysis in the liver has an important role to supply glucose to the circulation for a short fasting period (Shikama, Yajima and Ui 1980). The effects of insulin on supply of glucose from liver glycogen in the glucocorticoid-treated animal are not fully clear. In the present study, the liver of dexamethasone(Dex)-treated rats was isolated and perfused to examine sensitivity and responsiveness of the hepatic glucose output to insulin. Materials and Methods Male Wistar rats weighing 140 g were used throughout this study. The animals were divided into two groups. Dextreated rats were prepared by subcutaneous injection of dexamethasone 1 mg/kg (Merck & Co., NJ, USA) given every day at 18:00 for 7 days, and control rats were prepared by the injection of saline. The rat was housed under standard lights on 5:00—19:00, and maintained on standard chow. Rats, fed ad libitum, were anesthetized at 12:00— 15:00 with pentobarbital sodium and provided to the following studies. Glucose Tolerance
Glucose 0.5 g/kg was intravenously injected from the right femoral vein and blood samplings were carried out at 0,10,20 min from the left femoral vein. Liver
These results suggest that Dex-treatment augments hepatic glucose output, but does not affect the sensitivity and responsiveness of that to insulin. Key words Dexamethasone — Insulin — Liver Glycogen
Introduction Although several studies demonstrate that glucocorticoid treatment reduced glucose utilization and induced hyperinsulinemia, it is still controversial whether glucocorticoid treatment diminishes insulin action on the hepatic glucose production (Riddick, Reisler and Kipnis 1962; Shamoon, Soman and Sherwin 1980; Shamoon, Hendler and Sherwin 1980; Rizza, Mandarino and Gerich 1982; Pagano, CavalloPerin, Cassader, Bruno, Ozzello, Masciola, Dallomo and Imbimbo 1983). One of main effects of glucocorticoid is to inHorm.metab.Res.23(1991)53-55 © GeorgThiemeVerlag Stuttgart-New York
Test
Perfusion
According to the method of Misbin, Merimee and Lowenstein (1976), the liver was isolated and cyclically perfused with a medium consisting of 118 mM NaCl, 3.5 mM KC1, 1.2 mM MgSO4, 1.2 mM KH2PO4, 2.5 mM CaCh, 15.5 mM NaHCO3, 8.0 mM HEPES-NaOH (pH 7.4), 5 mM glucose and 3 % bovine serum albumin (fraction V, Sigma, St. Louis, USA), equilibrated with 95 % O2 + 5% CO2 gas using a moniliform glass oxygenator. After a washout perfusion for 10 min, 30 ml of perfusate was recirculated at aflowrate of 20 ml/min for 60 min. Porcine insulin (Novo, Denmark) was added to perfusate to maintain 100-40% of the concentration at start throughout the experiment (Fig. 2). Glycogen
Content
Liver glycogen was extracted with trichloroacetate solution and precipitated with ethanol (Stetten, Katzen and Stetten 1956). The precipitation was desicated and weighed. Plasma and perfusate glucose was determined by glucose oxidase method. Serum and perfusate insulin was assayed by a radioimmunoassay system using an anti-porcine insulin serum and porcine insulin for the standard. Student's t-test was used for statistics. Received: 30 May 1989
Accepted: 3 July 1990
Downloaded by: Universite de Sherbrooke. Copyrighted material.
O. Mokuda , Y. Sakamoto , T. Ikeda and H. Mashiba Third Department of Internal Medicine, Teikyo University School of Medicine, Chiba First Department of Internal Medicine, Tottori University School of Medicine, Yonago, Japan
Horm. metab. Res. 23 (1991)
Fig. 1 Intravenous glucose tolerance test. Control amethasone-treated (O) (mean + SD, n = 5).
O. Mokuda, Y. Sakamoto, T. Ikeda and H. Mashiba
• ); dex-
Fig. 2 Insulin extraction by liver of control ( • ) and dexamethasone-treated (O) rats. Insulin extraction rate was not different between control and dexamethasone-treated, and almost constant in a range of 20-500 (ill/ml (upper panel) and throughout perfusion period for 60 min at 500 uU/ml (lower panel) (mean±SD, n = 5).
Results Body weight of the Dex-treated rat was significantly smaller than the control rat (148 ± 15 g vs 173 + 6 g, P < 0.05). Liver weight was almost similar between Dex and control group (8.7 + 0.5 g and 9.1 + 0.7 g). Glycogen content in the liver was markedly increased in Dex group compared with that in control (115 ± 5 mg/g wet tissue vs 28 + 4 mg/g, P < 0.01). In glucose tolerance test, Dex-treated rats showed significant increases of plasma glucose and serum insulin level at each time compared with control rats (Fig. 1). As shown in Fig. 2, the liver of Dex-treated rats removed insulin from the perfusate to the same degree as that of control rats. Insulin extraction rate of the perfused liver was almost constant in a range of 20—500 mU/ml insulin concentration, and showed no remarkable changes for 60 min. According to this insulin clearance rate, supplement insulin was, every 15 min, added to the perfusate to maintain 100—40% of insulin level at the start of experiment. Effect of insulin on perfusate glucose is shown in Fig. 3. Perfusate glucose in the experiment of control rat liver was 23 + 2.0 mM without insulin and declined to reach the nadir level of 13 + 1.5 mM by the addition of 100 uU/ml insulin. In Dex-treated rat livers, perfusate glucose was 34.5 + 2.5 mM without insulin and reached the nadir level of 19 ± 3 mM at 100 u,U/ml insulin. The decrement in perfusate glucose in response to 100 uU/ml insulin was 10 m M (44% of the basal) in control and 15.5 mM (43 %) in Dex-treated. Discussion As commonly known, dexamethasone administration induced marked hyperglycemia and hyperinsulinemia in rats. Chap, Jones, Chou, Hartley, Entman and Field
Fig. 3 Effect of insulin on perfusate glucose (hepatic glucose output). Insulin concentration is the value at start of perfusion (mean + SD, n = 5).
(1986) noted in the study using conscious dogs that a decrease of hepatic insulin extraction contributed to hyperinsulinemia caused by dexamethasone treatment. Cam and Amatruda (1982) reported that insulin degradation was enhanced in hepatocytes from dexamethasone-treated rat. This study demonstrated that insulin extraction rate in Dex-treated rat liver was not changed. But we did not measure the effects of portal blood flow on insulin extraction rate in-vivo.
Downloaded by: Universite de Sherbrooke. Copyrighted material.
54
Horm. metab. Res. 23 (1991)
Treatment
Previous studies showed that glucocorticoids reduced the peripheral glucose utilization (Riddick, Reisler and Kipnis 1962; Shamoon, Soman and Sherwin 1980; Shamoon, Hendler and Sherwin 1980; Rizza, Mandarino and Gerich 1982; Pagano, Cavallo-Perin, Cassader, Bruno, Ozzello, Masciala, Dallomo and Imbimbo 1983), and some investigators concluded that glucocorticoids induced an insulin resistant state due to the inhibition of glucose transport system in peripheral tissue {Olefsky 1975; Nelson and Murray 1987). On the other hand, effects of glucocorticoids on the hepatic glucose output have not been sufficiently established. We obtained the finding that, in perfusion system, the sensitivity and responsiveness of the hepatic glucose output to insulin were not affected by dexamethasone treatment. Some in-vivo studies showed that glucocorticoids increased hepatic glucose output and decreased the insulin sensitivity in liver (Rizza, Mandarino and Gerich 1982; Chap et al. 1986), and other studies resulted in no significant influence on the hepatic glucose production (Shamoon, Soman and Sherwin 1980; Eigler, Sacca and Sherwin 1979; Pagano et al. 1983). The in-vitro studies, using cultured rat hepatocytes, showed that dexamethasone increased both the sensitivity and responsiveness of glycogen synthesis to insulin (Fleig, Nother-Fleig, Steudter, Enderle and Ditschuneit 1985) and inversely decreased both the sensitivity and responsiveness of aminoisobutyrate uptake to insulin (Cam and Amatruda 1982), or increased the responsiveness of lipogenesis to insulin but decreased the sensitivity of that (Amatruda, Danahy and Chang 1983). Hepatic glycogen deposition is accelerated by glucocorticoids together with the simultaneous elevation of portal venous glucose and insulin level (Shikama, Yajima and Ui 1980). Moreover, glucocorticoids increase the circulating glucagon, amino acids, and free fatty acids giving some influences on hepatic glucose metabolism (Marco, Calle, Roman, Diaz-Fierros, ViUanueva and Valverde 1973; Wise, Hendler and Felig 1973; Venkatesan, Davidson and Hutchinson 1987). Therefore the confliction of these results is thought to be caused by differences of methods, i. e., fed/fasted, in-vivo/in-vitro, cultured hepatocytes/perfused liver, in-vitro treatment/in-vivo administration of glucocorticoid and durations of administration (Ninomiya, Forbath and Hetenyi 1965; Venkatesan, Davidson and Hutchinson 1987). In our preliminary study, after an overnight fasting the rat liver glycogen content was extremely exhausted (6 + 2 mg/g) and the basal hepatic glucose output was negligible, i. e., perfusate glucose was 4.9 + 0.9 mM without insulin in the same experiment. Therefore, it was thought that this experiment was designed to observe mainly hepatic glycogenolysis and to omit humoral factors. In the Dex-treated rat liver, the acceleration of basal glucose output seemed to be related to perfuse the glycogen-rich liver with a medium containing 5 mM glucose. In further studies, it is required to correct the perfusate glucose concentration to the basal plasma glucose level.
Caw, J. F., J. M. Amatruda: Glucocorticoid-induced insulin resistance. The importance of postbinding events in the regulation of insulin binding, action, and degradation in freshly isolated and primary cultures of rat hepatocytes. J. Clin. Invest. 69: 866-875 (1982) Chap, Z., R. H. Jones, J. Chou, C. J. Hartley, M. L. Entman, J. B. Field: Effect of dexamethasone on hepatic glucose and insulin metabolism after oral glucose in conscious dogs. J. Clin. Invest. 78:1355— 1361 (1986) Eigler, N, L. Sacca, R. S. Sherwin: Synergistic interactions of physiologic increments of glucagon, epinephrine, and Cortisol in the dog. J. Clin. Invest. 63:114-123 (1979) Fleig, W. E., G. Nother-Fleig, S. Steudter, D. Enderle, H. Ditschuneit: Regulation of insulin binding and glycogenesis by insulin and dexamethasone in cultured rat hepatocytes. Biochim. Biophys. Acta 847:352-361(1985) Marco, J., C. Calle, D. Roman, M. Diaz-Fierros, M. L. ViUanueva, I. Valverde: Hyperglucagonism induced by glucocorticoid treatmentinman.NewEngl.J.Med.288:128-131 (1973) Misbin, R. I., T. J. Merimee, J. M. Lowenstein: Insulin removal by isolated perfused rat liver. Am. J. Physiol. 230:171 -177 (1976) Nelson, D. H., D. K. Murray: Dexamethasone inhibition of hydrogen peroxide-stimulated glucose transport. Endocrinology 120: 156— 159(1987) Ninomiya, R., N. F. Forbath, G. Hetenyi: Effect of adrenal steroids on glucose kinetics in normal and diabetic dogs. Diabetes 14: 729— 739(1965) Olefsky, J. M.: Effect of dexamethasone on insulin binding, glucose transport, and glucose oxidation of isolated rat adipocytes. J. Clin. Invest. 56:1499-1508(1975) Pagano, G., P. Cavallo-Perin, M. Cassader, A. Bruno, A. Ozzello, P. Masciola, A. M. Dallomo, B. Imbimbo: An in vivo and in vitro study of the mechanism of prednisone-induced insulin resistance in healthy subjects. J. Clin. Invest. 72:1814-1820 (1983) Riddick, F. A., D. M. Reisler, D. M. Kipnis: The sugar transport system in striated muscle: Effect of growth hormone, hydrocortisone and alloxan diabetes. Diabetes 11: 171-178(1962) Rizza, R. A., L. J. Mandarino, J. E. Gerich: Cortisol-induced insulin resistance in man: Impaired suppression of glucose production and stimulation of glucose utilization due to a postreceptor defect of insulin action. J. Clin. Endocrinol. Metab. 54:131-138(1982) Shamoon, H., R. Hendler, R. S. Sherwin: Altered responsiveness to Cortisol, epinephrine, and glucagon in insulin-infused juvenileonset diabetics. Diabetes 29:284-291 (1980) Shamoon, H, V. Soman, R. S. Sherwin: The influence of acute physiological increments of Cortisol on fuel metabolism and insulin binding to monocytes in normal humans. J. Clin. Endocrinol. Metab. 50:495-501(1980) Shikama, H, M. Yajima, M. Ui: Glycogen metabolism in rat liver during transition from the fed to fasted states. Biochim. Biophys. Acta631:278-288(1980) Stetten, M. R., H. M. Katzen, D. Stetten: Metabolic inhomogeneity of glycogen as a function of molecular weight. J. Biol. Chem. 222: 587-599(1956) Venkatesan, N, M. B. Davidson, A. Hutchinson: Possible role for the glucose-fatty acid cycle in dexamethasone-induced insulin antagonism in rats. Metabolism36:883-891 (1987) Wise, J. K., R. Hendler, P. Felig: Influence of glucocorticoids on glucagon secretion and plasma amino acid concentrations in man. J. Clin. Invest. 52:2774-2782 (1973) Requests for reprints should be addressed to:
O. Mokuda 3rd Dept. of Internal Medicine Teikyo University Amatruda, J. M., S. A. Danahy, C. L. Chang:Thz effects of glucocortiIchihara-City coids on insulin-stimulated lipogenesis in primary cultures of rat Chiba 299-01 (lapan) hepatocytes. Biochem. J. 212:135-141 (1983) References
55
Downloaded by: Universite de Sherbrooke. Copyrighted material.
Hepatic Glucose Output in Dexamethasone
