[Effect of soy isoflavones on cAMP/PKA pathway in breast cancer cells of the rat.].

Soy isoflavones have been reported to be natural chemopreventive in several types of human cancer. Daidzein and genistein are two main components of soy isoflavones. In our previous study, they were shown to be anti-proliferative and induce cell cycle arrest at S phase of SHZ-88 rat breast cancer cells. We hypothesized that soy isoflavones might exert its anticancer effect by activating cAMP/PKA pathway. The present study was designed to analyze the effect of soy isoflavones on the cAMP/PKA pathway in SHZ-88 cells. Daidzein and genistein were dissolved in DMSO. Cells were treated with 50 mug/ml daidzein and 15 mug/ml genistein, respectively, and with only equal DMSO in the culture medium as control. The cellular cAMP content was tested by radioimmunoassay (RIA). The activity of adenylate cyclase (AC), phosphodiesterase (PDE) and PKA were measured by RIA and (gamma-(32)P) ATP incorporation. Reverse transcript-polymerase chain reaction (RT-PCR) was used to analyze the expression of cAMP response element binding protein (CREB) mRNA of the cells. The results showed that the concentration of cAMP in the cells treated with 50 mug/ml daidzein and 15 mug/ml genistein was significantly increased by 9.5%and 11.0%, respectively, 5 min later (P<0.05), then increased by 31.0%and 40.3%, respectively, 10 min later (P<0.01), compared with that of the control group cells. The activity of AC was not affected during the course of experiment, but that of PDE was decreased to 71.8%and 71.6%, respectively, in the control group 5 min later (P<0.05). The PKA activity was increased to 125.8%and 122.3%, respectively, in the control group 20 min after the cells were treated with daidzein and genistein (P<0.05), and kept at high level till 40 min after treatment. CREB mRNA of the cells treated with daidzein and genistein was increased by 31.6%and 51.1%, respectively, 3 h later (P<0.05), then began to decrease 6 h after treatment. The current study suggests that soy isoflavones activate the cAMP/PKA pathway in SHZ-88 rat breast cancer cells by inhibiting the activity of phosphodiesterase.

[Effects of clenbuterol on nitrogen metabolism and G6PDH activity of rat hepatocyte].

AIM: To study the effects of beta 2-adrenergic receptor-selective agonist clenbuterol on nitrogen metabolism and glucose-6-phosphate dehydrogenase activity of rat hepatocyte and its pharmacological mechanism. METHODS: Biochemical methods were used to study the influence of clenbuterol on urea-nitrogen concentration of hepatocyte culture medium, 3H-leucine incorporation into hepatocyte, insulin-like growth factor I (IGF-I) production and glucose-6-phosphate dehydrogenase (G6PDH) activity of rat hepatocyte. RESULTS: The results showed that urea-nitrogen production by cultured rat hepatocytes was markedly affected with clenbuterol treatment (1 x 10(-6) mol.L-1), urea-nitrogen concentration of culture medium was decreased by 25.51% (P < 0.05) compared with control. The inhibitory effect of hepatocyte urea-nitrogen production of clenbuterol was blocked by propranolol, a beta-adrenoreceptor antagonist (1 x 10(-6) mol.L-1), but hepatocyte urea-nitrogen level was not affected with propranolol treatment only (P > 0.05). The content of 3H-leucine incorporation in rat hepatocyte was significantly increased by 23.35% (P < 0.05) with clenbuterol-treatment (1 x 10(-6) mol.L-1), and the enhanced effect of 3H-leucine incorporation into hepatocyte was antagonized by propranolol (1 x 10(-6) mol.L-1. The level of 3H-leucine incorporation of rat hepatocyte was not influenced by propranolol alone. IGF-I production of rat hepatocyte might be affected by clenbuterol. IGF-I concentration of culture medium was increased by 39.46% with clenbuterol (1 x 10(-6) mol.L-1), but no significant difference was found compared with the control (P > 0.05). Moreover, G6PDH activity of rat hepatocyte was significantly decreased by 43.36% (P < 0.05) with clenbuterol treatment (1 x 10(-6) mol.L-1), and the declined effect of clenbuterol was antagonized by propranolol. G6PDH activity of rat hepatocyte was not affected on condition that propranolol was administered alone (P > 0.05). CONCLUSION: It is suggested that clenbuterol may regulate nitrogen and fat metabolism by means of increasing nitrogen retention and protein synthesis, and decreasing G6PDH activity of rat hepatocyte for pharmacological effects.

[Effect of cysteamine on the pancreatic secretion and enzymatic activity in geese].

AIM: To know the effect of cysteamine on the pancreatic secretion and enzyme activity in geese. METHODS: Eight adult geese fitted chronic pancreatic and duodenal cannulas were used to evaluate the effect of cysteamine (CS) on the pancreatic secretion and enzyme activity. The experiment was consist of control and treated phase. CS was added in the diet at the dosage of 100 mg/kg bw on the first day of treated phase. The birds were free fed at daytime (8:00-20:00) and fasted at nighttime (20:00-8:00). The pancreatic juice samples were collected continuously for three days in each phase. RESULTS: CS increased the average rate of pancreatic secretion by 240.16% (P < 0.01), in which that of daytime was elevated by 234.45% (P < 0.01), while that of nighttime elevated by 253.70% (P < 0.01). The secretion volume at daytime was more than that of night. CS increased trypsin activity by 49.05% (P < 0.01), whereas lipase and amylase activity was reduced by 25.44% (P < 0.01) and 21.95% (P < 0.01) separately. The one hour total activity of trypsin, lipase and amylase were elevated by 406.88% (P < 0.01), 153.58% (P < 0.01) and 166.59% (P < 0.01) respectively. Ratios of pancreatic secretion were different between day and night. CONCLUSION: These results indicate that CS can affect the pancreatic juice secretion and pancreatic enzyme activity by depleting the somatostatin, so that benefits to improve the digestive foundation and supply more nutrition for quickly growing in geese.

[Effects of clenbuterol on the metabolism of nitrogen and IGF-I level in isolated perfused rat liver].

AIM: To examine the liver mechanism with which clenbuterol is explained how to affect growth metabolism. METHODS: Twenty-four adult SD rats were randomly divided into three groups, a control and two treatment groups. The technique of isolated perfused rat liver in vitro was used to study the effects of clenbuterol on urea nitrogen concentration of perfused medium, GPT activity and synthesis and secretion of IGF-I in isolated perfused rat liver. RESULTS: Urea-nitrogen concentration of perfused medium was significantly affected by clenbuterol in a dose-dependent and time-dependent manner. The urea-nitrogen level was decreased by 15.02% (P > 0.05),17.97% (P > 0.05), 26.76% (P < 0.05) and 30.08% (P < 0.01) for 1 h, 2 h, 3 h, 4 h after administering clenbuterol at the dose of 1 x 10(-6) mol/L, respectively, compared to that of control. 1 x 10(-8) mol/L CL had the similar effect on urea-nitrogen level. GTP activity of isolated perfused rat liver was inhibited by clenbuterol. The enzyme activity was decreased by 24.65% (P < 0.05) at the dose of 1 10(-6) mol/L CL in clenbuterol-treated 4h. The production and secretion of IGF-I were also influenced by clenbuterol in isolated perfused rat liver. IGF-I concentration of rat liver was increased by 19.77% (P < 0.05) in 4 h clenbuterol treatment (1 x 10(-6) mol/L). Meanwhile, IGF-I concentration of perfusion medium was also elevated though the difference was not significant compared with control. CONCLUSION: It is suggested that clenbuterol may improve growth metabolism by means of increasing nitrogen retention and enhancing IGF-I production and secretion of rat liver.

[Effects of clenbuterol on the hepatic flux of nitrogen, VFA and glucose in sheep].

AIM: To examine the liver mechanism with which clenbuterol (CL) is explained how to affect growth metabolism. METHODS: The technique of chronic poly catheter was used to study the effects of CL (0.8 mg/kg b w) on the hepatic flux of nitrogen, VFA and glucose in 4 sheep. RESULTS: The urea-nitrogen flux in CL-treated period always was lower than that in control during 24 h. The average flux of urea-nitrogen in hepatic and portal vein were decreased by 16.86% (P < 0.01) and 15.51% (P < 0.05), respectively, compared with that of control. The peptide level in hepatic vein was decreased with the treatment of CL, average flux of peptide was decreased by 38.71% (P < 0.01). But the peptide level of portal vein in CL treatment period was similar to control. Moreover, VFA level in the portal vein was enhanced by CL, the average flux of acetate in portal vein was increased by 19.49% (P < 0.01). No difference of VFA level in hepatic vein was noted between CL-treated period and control. In addition, the glucose flux in hepatic vein was obviously increased with CL treatment, the average flux of glucose was increased by 25.96% (P < 0.01). And glucose flux in portal vein was also elevated during CL-treated period. CONCLUSION: CL can affect growth metabolism of animal with increasing nitrogen deposition, improving absorption and utilization of VFA and enhancing glucose synthesis in sheep liver.

[Effects of cysteamine on the plasma levels of SS and some metabolic hormones in adult geese].

AIM: To know the effect of cysteamine (CS) on the plasma levels of somatostatin (SS) and some metabolic hormones in adult geese. METHODS: Fourteen adult crossbred geese (Chuan white x Tai lake) fitted with chronic wing vein cannulas were used in this study to evaluate the effect of CS on SS, TSH, T3 and T4 levels. The experiment was consisted of control and treated phase. The diet was added CS at dosage of 100 mg/kg bw on the first day of the treated phase. The blood samples were collected from the cannulas and analyzed by radioimmunoassay. RESULTS: The plasma SS concentration was (1.87 +/- 0.10) microg/L in control phase. Whereas SS concentrations on day 1, 3, 5, 7 of treated phase were decreased markedly (P < 0.05 or P < 0.01). Thereafter it was rose on the seventh day, however it was still lower than that of control. The thyroid stimulating hormone (TSH) content (2.45 +/- 0.31 mIU/L) was significantly decreased by 21.63% (P < 0.01) on day 1, and 18.37% (P > 0.05) on day 3 and day 5. Comparing with control phase (5.41 +/- 0.98 microg/L), T4 contents were elevated by 60.26% (P < 0.01), 43.25% (P < 0.01), 37.15% (P < 0.01) and 16. 82% (P < 0.01) respectively on day 1, 3, 5, 7. T3 level was (1.05 +/- 0.06) microg/L in control phase, whereas the levels was significantly increased by 36.19% (P < 0.01) on day 3. Also, the insulin concentration was higher than that of control (4.43 +/- 0.41 mU/ L) by 18.28% (P < 0.05) on the day 5. CONCLUSION: These results indicate that CS can decrease the plasma SS and TSH levels, whereas increase the levels of T4, T3 and insulin, therefore change metabolism, improve the nutrition transform and accelerate the growth in geese.