Cataracts and hypertension in salt-sensitive rats. A possible ion transport defect.

In previous unrelated studies, we observed a 35 to 50% incidence of cataract formation in several groups of Dahl salt-sensitive hypertensive rats (DS) over a 4-year period. In the present study we evaluated longitudinal changes in blood pressure in DS in which cataracts eventually developed and those in which cataracts did not develop when all animals were maintained on a high sodium diet. Lenses were evaluated by slit-lamp microscopy to determine if cataractous lesions were similar among rats, to classify lesion types, and to define the age at which cataracts were detectable in DS. The possible participation of several cataractogenic risk factors as major influences on cataract formation also was evaluated. Finally, aqueous humor concentrations and lenticular content of sodium and potassium were determined to evaluate the possibility that a defect in ion transport at the lens epithelium and ciliary body might play a role in cataractogenesis in DS, since ion transport defects have been shown to lead to lens opacification in other models of genetic and experimental cataracts. Parallel studies were performed in Dahl salt-resistant control rats (DR). A high incidence of cataract formation was found in DS. Although systolic blood pressure was not consistently greater in adult DS with cataracts compared with values in age-matched DS without cataracts, the initial pressor response to a high salt diet was greatest in weanling DS in which cataractous lesions later developed. Slit-lamp analysis revealed that cataracts in this genetic model were cortical, with one mixed cortical, nuclear lesion. Posterior subcapsular lesions were not observed, suggesting that lesions were not steroid-induced.(ABSTRACT TRUNCATED AT 250 WORDS)