Tyrosine supplementation in chronic experimental uremia

The occurrence of low tyrosine tissue levels in uremic subjects, possibly due to impaired phenylalanine hydroxylation, suggests that tyrosine may be an essential amino acid in uremia. Additional dietary tyrosine may thus re-dress the deficiency. This study examined growth and tyrosine/phenylalanine metabolism in uremic rats during tyrosine supplementation. Rats made uremic (U) by 7 8 nephrectomy were compared to pair-fed (C P) and ad libitum-fed (C A), sham-operated controls. Two sets of each group of rats were studied after 21 days on the resepctive diets: I = Purina Lab Chow; II = same + 3.5% tyrosine. Plasma tyrosine was below normal in U and C P-fed diet I. With diet II, the tyrosine: phenylalanine ratio in U was lower than both C A and C P. In rats fed diet II, the tyrosine: phenlalanine ratio became indistinguishable among the three groups. Growth parameters in U and C P were similar, regardless of the diet. Body weight gain, tibial length, muscle mass, and tissue protein did not improve in uremic animals supplemented with tyrosine. The specific activity of liver phenylalanine hydroxylase in U was not different from C A or C P. However, loss of cortical renal mass appeared to be the major determinant of decreased kidney phenylalanine hydroxylation in experimental uremia. This alteration is likely to be the greatest contributory factor to the alteration of plasma levels of tyrosine and phenylalanine. The data presented do not support a proposed essentiality of tyrosine in uremia

Improved water and sodium absorption from oral rehydration solutions based on rice syrup in a rat model of osmotic diarrhea

Rice syrup solids, rice protein, and casein hydrolysate were added to experimental oral rehydration solutions in various combinations and tested in a rat intestinal perfusion system. Chronic osmotic diarrhea was induced in juvenile rats by supplying the cathartic agents, magnesium citrate and phenolphthalein, in their drinking water for 1 week. The experimental oral rehydration solutions were compared with standard oral rehydration solutions containing 20 gm/L or 30 gm/L of glucose and with each other to determine if there were significant differences in net water, sodium, or potassium absorption. An oral rehydration solution containing 30 gm/L of rice syrup solids had a net water absorption rate significantly higher than that of the standard 20 gm/L glucose-based oral rehydration solution (2.1±0.62 versus 1.5±0.48 μl/[min x cm], p<0.05). Casein hydrolysate did not significantly affect net water absorption. However, combinations of 30 gm/L rice syrup solids and 5 gm/L casein hydrolysate significantly increased ( p<0.05) net sodium and potassium absorption compared with the 20 gm/L glucose-based oral rehydration solution but not versus rice syrup solids alone. Oral rehydration solutions containing 30 gm/L rice syrup solids plus 5 gm/L rice protein, and 30 gm/L rice syrup solids plus 5 gm/L casein hydrolysate, had net water absorption rates significantly higher than the rate of a 30 gm/L glucose-based oral rehydration solution (2.5±0.36 and 2.4±0.38, respectively, versus 0.87±0.40 μl/[min x cm], p<0.05). Rice protein and casein hydrolysate, however, did not significantly affect net water, sodium, or potassium absorption when added to rice protein glucose-based oral rehydration solutions. An inverse correlation between osmolality and net water absorption was observed ( r=−0.653, p<0.02). The data suggest that substitution of rice syrup solids for glucose in oral rehydration solutions will improved water absorption and that rice syrup solids in combination with protein hydrolysates may, in addition, promote better sodium and potassium uptake

The Role of Dietary Zinc in Modifying the Onset and Severity of Spontaneous Diabetes in the BB Wistar Rat

The goal of this study was to determine whether zinc supplementation in the diet of diabetes-prone BB Wistar rats will delay or prevent the onset of overt diabetes. Male Wistar BB rats were fed diets containing either 1000 ppm (HZ), 50 ppm (NZ), or 1 ppm zinc (LZ) starting at 30 days of age. Non-diabetes-prone rats were fed NZ and designated as controls (NORM). Beginning at 60 days, the rats were checked for glycosuria and, if positive, were given an ip glucose tolerance test (IPGTT). All remaining animals underwent an IPGTT at 100 days and were sacrificed. At 90 days of age HZ rats had a lower incidence of diabetes (19%) than NZ (53%) or LZ (44%) animals (P< 0.015). By age 100 days, for the HZ group, there was a 60% reduction in the number of expected overt diabetic rats. HZ animals also had higher concentrations of both pancreatic and serum insulin and exhibited lower serum glucose and triglycerides. Immunohistochemistry of HZ rats was clearly different from NZ rats and showed evidence of nearly normal pancreatic endocrine activity. Data indicate that dietary treatment of diabetes-prone BB Wistar rats with zinc appears to be an effective approach for delaying or preventing the onset of diabetes in genetically predisposed rodents. This finding may suggest further experimental studies regarding dietary means for preservation of pancreatic function