Modelling cortical cataractogenesis 21: in diabetic rat lenses taurine supplementation partially reduces damage resulting from osmotic compensation leading to osmolyte loss and antioxidant depletion.

The concentration of taurine and the amino acids, glutathione, cysteine, ascorbate and ATP were determined in the lenses of rats made diabetic with streptozotocin. In the clear lenses, prior to vacuole formation after 1 or 2 weeks of diabetes, the increase in concentration of sorbitol and the total decrease of all these osmolytes were not significantly different. The major components of the osmolytes lost were taurine and amino acids, which together accounted for over 75% of the total osmolyte loss. Since glutathione, ascorbate, taurine and cysteine have been reported to have antioxidant activity, it appears that their loss may potentiate damage occurring as a result of free radicals generated by nonenzymic glycation by the Maillard reaction. Amino acids also lost as a result of the osmotic compensation, are estimated to be responsible for almost half of the antioxidant activity lost. To test this hypothesis, normal and streptozotocin diabetic female Wistar rats were given taurine at 0.05% or 0.10% (w/w) in the diet. This treatment resulted in small only marginally significant increases in serum taurine levels. At the end of 6 weeks the rats were examined for weight gain or loss and at the time of killing, blood was collected for measurement of serum glucose. gamma-Crystallin levels were determined in vitreous and aqueous humours using a radioimmunoassay. A lens from each rat was homogenized in 8 m guanidinium chloride for adenosine triphosphate (ATP) analysis. In normal rats, a small amount of gamma-crystallin was found in the vitreous humour, and an even smaller amount in the aqueous humour. Diabetes caused a 4- to 5-fold increase in the vitreous humour and a 4-fold increase in gamma-crystallin in the aqueous humour. Diabetes also led to a significant worsening in general body condition, loss of body weight, formation of cataracts, and decrease in lens ATP levels. Addition of taurine to the diet of diabetic animals resulted in a significant decrease of gamma-crystallin leakage into the vitreous but not the aqueous humour. Taurine had no effect on the lens ATP levels. Neither streptozotocin diabetes nor taurine in the diet appeared to affect the weight of the lenses.

Modelling cortical cataractogenesis. XII: Supplemental vitamin A treatment reduces gamma-crystallin leakage from lenses in diabetic rats.

Normal and streptozotocin diabetic female Wistar rats were given normal diets with the following additions: 0, or 12,500 iu/kg food vitamin A (retinyl palmitate). At the end of 6 weeks, the rats were examined for weight gain or loss, general body condition, and cataracts. At sacrifice, blood was collected for measurement of serum glucose. gamma-Crystallin levels were determined in aqueous and vitreous humours using a radioimmunoassay. One lens (the right) was homogenized in 8 M guanidinium chloride for ATP analysis. In normal rats, gamma-crystallin was detected in both aqueous and vitreous humours, with a greater concentration found in the vitreous. Diabetes caused a 4-5 fold increase in gamma-crystallin in both aqueous and vitreous humours. Diabetes also led to a significant loss of body weight, and decrease in lens ATP levels. Addition of vitamin A to the diet resulted in reduction in gamma-crystallin leakage into the aqueous and vitreous humours. Vitamin A at 12,500 iu/kg food resulted in an increase in lens ATP for the diabetic rats. Neither streptozotocin diabetes nor vitamin A in the diet appeared to affect the weight of the lenses after 6 weeks. It is suggested that childhood vitamin A deficiency leading to latent fiber cell damage may be an important factor contributing to the high incidence of cataracts in the third world.

Modelling cortical cataractogenesis. XI. Vitamin C reduces gamma-crystallin leakage from lenses in diabetic rats.

Normal and streptozotocin diabetic female Wistar rats were given vitamin C (VC) at 0.3% or 1.0% (w/w) in the diet: 1% dietary VC resulted, in 12-24 hr, in significant increases in serum ascorbate levels and lens ascorbate concentrations in normal rats. The increase was biphasic, with VC concentrations falling to a lower level which was still significantly elevated compared to controls in the period of 1.7-4 days for serum and 1.7-5 days for lenticular VC. At the end of 10 weeks the rats were examined for weight gain or loss, general body condition and cataracts. At the time of killing, blood was collected for measurement of serum glucose. Alpha-crystallin levels were determined in vitreous and aqueous humours using a radioimmunoassay. One lens from each rat was fixed for either scanning electron microscopy or light microscopy; the other lens was homogenized in 8 M guanidinium chloride for adenosine triphosphate analysis. In normal rats, a small amount of gamma-crystallin was found in the vitreous humour, and an even smaller amount in the aqueous humour. Diabetes caused a five-fold increase in the vitreous humour and a 2.5-fold increase in gamma-crystallin in the aqueous humour. Diabetes also led to a significant worsening in general body condition, loss of body weight, formation of cataracts, and decrease in lens adenosine triphosphate levels. Addition of VC to the diet of diabetic animals resulted in reduction in cataracts and a decrease of gamma-crystallin leakage into the aqueous and vitreous humours. VC had no effect on lens adenosine triphosphate levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Modeling cortical cataractogenesis: IX. Activity of vitamin E and esters in preventing cataracts and gamma-crystallin leakage from lenses in diabetic rats.

Normal and streptozotocin diabetic female Wistar rats were given vitamin E in the diet as the tocopherol, acetate, or succinate form (2,850 IU/kg food). At the end of 6 weeks, the rats were examined for weight gain or loss, general body condition, and cataracts. At sacrifice, blood was collected for measurement of serum glucose, and gamma-crystallin levels were measured in aqueous and vitreous humors using a radioimmunoassay. One lens was homogenized in 8 M guanidinium chloride for ATP analysis. In normal rats, gamma-crystallin was detected in both aqueous and vitreous humors, with the higher concentration in the vitreous humor. Diabetes caused a sixfold increase in gamma-crystallin in both the aqueous and vitreous humors. Diabetes also led to a significant worsening in general body condition, loss of body weight, formation of cataracts, and decrease in lens ATP levels. Addition of vitamin E and vitamin E succinate, but not vitamin E acetate, to the diet resulted in reduction of gamma-crystallin leakage into the vitreous humors and an increase in body weight. There was no improvement noted for the lens ATP levels, the general body condition, or visual cataract score. Neither streptozotocin-induced diabetes nor vitamin E in the diet appeared to affect the weight of the lenses.

Modelling cortical cataractogenesis VIII: effects of butylated hydroxytoluene (BHT) in reducing protein leakage from lenses in diabetic rats.

Normal and streptozotocin diabetic female Wistar rats were given butylated hydroxytoluene at 0-, 0.067- or 0.50% w/w in the diet. At the end of 10 weeks, the animals were examined for weight gain or loss, general body condition, and cataracts. After death, blood was collected for measurement of serum glucose. gamma-Crystallin was determined in aqueous and vitreous humours using a radioimmunoassay. One lens from each rat was homogenized in 8 M guanidinium chloride for adenosine triphosphate analysis. In normal rats, there is a small amount of gamma-crystallin found in the vitreous humour, and an even smaller amount in the aqueous humour. Diabetes caused a 2.5-fold increase of gamma-crystallin in the aqueous humour and a five-fold increase in the vitreous humour. Diabetes also led to a significant worsening in general body condition, loss of body weight, decrease in lens adenosine triphosphate levels, and formation of cataracts. Addition of butylated hydroxytoluene (BHT) to the diet resulted in improved general body condition, reduction in cataracts, decrease of gamma-crystallin leakage into the vitreous humour, and weight gain. There was no effect of dietary butylated hydroxytoluene on levels of lens adenosine triphosphate. Neither the diabetic state nor treatment with butylated hydroxytoluene affected the weight of the lenses.

The use of guanidinium chloride in the preparation of stable cellular homogenates containing ATP.

Rat eye lenses were prepared for ATP determination by homogenization in 8 M guanidinium chloride-0.01 M EDTA. Standards of ATP were made up in the same solution. ATP appears to be quite stable in this solution in both standards and lens homogenates whether storage is at room temperature, 4 degrees C, or -20 degrees C for up to several weeks. ATP was measured using a luciferin-luciferase preparation in Hepes buffer, pH 7.75. The photons of light produced were detected by a bioluminescence counter.

Urinary cyclic AMP and cyclic GMP in normal and asthmatic subjects during exercise.

The purpose of this study was to compare exercise-induced changes in urinary cyclic AMP and cyclic GMP of normal and asthmatic subjects. All subjects were exercised to 80% of predicted maximum heart rate for 15 minutes on a bicycle ergometer. FEV1 was measured before and after exercise to determine the degree of bronchoconstriction due to exercise. Five urine specimens were collected by voluntary voiding at 20 minute intervals (one specimen before exercise and four after exercise). Before exercise, the asthmatic subjects excreted less cyclic GMP (p less than 0.05) but the same cyclic AMP as the normal subjects. Creatinine excretion in nine asthmatic subjects decreased by 24% (p less than 0.01) during exercise. In sixteen normal subjects (post-exercise bronchoconstriction less than 10%) cyclic AMP excretion increased by 19% (p less than 0.05) within 20 minutes after exercise, while cyclic GMP excretion did not change significantly. In thirteen asthmatic subjects (post-exercise bronchoconstriction greater than 20%) cyclic AMP excretion did not change significantly, while cyclic GMP excretion increased by 23% (p less than 0.05) within 20 minutes after exercise. This study has shown that exercise affects the excretion of cyclic AMP, cyclic GMP, and creatinine in normal and asthmatic subjects. The response of normal and asthmatic groups to exercise was the same for creatinine but different for cyclic AMP and cyclic GMP.