Nitric oxide donors can enhance the intestinal transport and absorption of insulin and Asu1,7-eel calcitonin in rats,Author： Gihan Fetih Fawsia Habib Naoki Okada Takuya Fujita Mohammed Attia Akira Yamamoto,Journal of Controlled Release,Volume 106, Issue 3, 2 September 2005, Pages 287297,The characteristics of three NO donors, NOC5 NOC12 SNAP as absorption enhancers for peptide drugs were examined in rats .Insulin and Asu1,7-eel calcitonin (ECT) were used as a model drug to investigate the effectiveness of the tested enhancers.Experimental method：a modified Ussing chamber method and an in situ closed loop method. Conclution： NO donors possess excellent effectiveness for the use as absorption enhancers of peptide drugs and they are very effective at lower.,Abstract,Essay map,NO,ECT,Insulin,Concentration,Absorption position,NO scavenger,NO scavenger,1、Experimental notes-1：,three NO donors：,3-(2-hydroxy-1-(1-methylethyl)-2-nitrosohydrazino)-1-propanamine (NOC5), C6H16N4O2,N-ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino)-ethanamine (NOC12) C6H16N4O2,S-nitroso-N-acetyl-DL-penicillamine (SNAP),model drugs：,Insulin and Asu1,7-eel calcitonin (ECT),2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide, sodium salt (carboxy-PTIO),NO scavenger:,C7H12N2O4S,1 Experimental notes-2：,1 Experimental notes-3：,Papp = (dXR/dT) (1/ACo),XR is the amount of drug in moles in the receptor side,A is the diffusion area in square centimeters,Co is the initial concentration of drug in the donor side,Papp is the apparent permeability coefficient in centimeters per second,The pharmacological availability (PA%),The area above the hypoglycemic (or hypocalcemic) effect (%)- time curve (AAC),2、Methods-1,Illustration of a biopsy sample loaded into the Ussing chamber. The intestinal biopsy was placed in the center of the supporting disc, covering the transversal lumen of the Ussing chamber completely and dividing the solution into two compartments.,drug solution,PBS,a modified Ussing chamber method,2、Methods-2,an in situ closed loop method,insulin (0.1 IU/rat, ECT (0.1 g/rat).,A closed loop,NO donors,obtain the plasma fraction (100 l),Plasma glucose concentrations,the glucose oxidase method,Plasma calcium concentrations,Wako Calcium C test,2、Methods-3,At pre-determined times up until 180 min,The resulting mixture was centrifuged at 10,000 rpm for 5 min to remove the precipitated protein,Result-3.1 Effect of NO donors on the permeability of insulin across the intestinal membranes,Fig. 1. Regional differences in the effects of NO donors (0.1 mM) on the permeability of insulin across different intestinal membranes.,Fig. 2. Effect of various concentrations of NO donors on the permeability of insulin across the colonic membrane,() NOC5, () NOC12 and () SNAP,Result-3.1 Effect of NO donors on the permeability of insulin across the intestinal membranes,SNAP was the most effective enhancer The absorption-enhancing effects were concentration-dependent over the range of 0.01 to 0.1 mM.,Result-3.2. Effect of carboxy-PTIO on the absorption enhancing effect of NO donors,Fig. 3. Effect of carboxy-PTIO (c-PTIO) on the permeability of insulin across the colonic membrane in the presence of NO,These findings suggested that the absorption enhancing effects of NO donors on insulin permeability might be mediated by the action of NO.,Result-3.3. Effects of NO donors on the intestinal absorption of insulin,Fig. 4. Concentration-time profiles of glucose in plasma following administration of insulin with or without NO donors to different sites. Keys: () control, () NOC5, () NOC12, () SNAP.,The extent of absorption was greatly improved by NO donors from all loops, but the greatest enhancement was obtained in the colon.,Result-3.3. Effects of NO donors on the intestinal absorption of insulin,Fig. 5. Effect of various concentrations of NO donors on the pharmacological availability % (PA%) following administration of insulin (20 IU) to the rat colon Dotted line represents the level of insulin PA% without NO donors (control). Keys: () NOC5, () NOC12 and () SNAP,Result-3.3. Effects of NO donors on the intestinal absorption of insulin,Concentration dependency of NO donors was examined for the colonic absorption of insulin,Fig. 6. Effect of 10 mM carboxy-PTIO (c-PTIO) on the pharmacological availability % (PA%) of insulin after administration to the rat colon with NO donors (5 mM)., significantly different compared with the control, (n.s.) not significantly different compared with the control.,Result-3.3. Effects of NO donors on the intestinal absorption of insulin,the absorption enhancing effect of NO donors on insulin absorption may be mediated by the action of NO.,Result-3.4. Stability of insulin in the intestinal mucosal homogenates in the presence of NO donors,Fig. 7. Effect of NO donors (5 mM) on the degradation of insulin (0.02 mM) in the small and large intestinal homogenates. Each point is the mean of four experiments. Keys: () control, () NOC5, () NOC12, () SNAP.,