Lenticular Rubidium Uptake and Plasma Renin Activity in Weanling Cataract-Prone Salt-Sensitive Rats

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 15; no. 2 Suppl I; pp. I-144 - I-148
• Main Authors: Sargent, Carmen Rodriguez, Estape, Estela S, Santiago, Angel Rodriguez, Ramos, Victor L, Irizarry, Jaime E, Cangjano, Jose L, Maldonado, Manuel Martinez
• Format: Journal Article
• Language: English
• Published: United States American Heart Association, Inc 01.02.1990
• Subjects: Animals; Blood Pressure; Cataract - genetics; Cataract - metabolism; Cataract - physiopathology; Disease Susceptibility; Drug Resistance; Female; Lens, Crystalline - metabolism; Ouabain - pharmacology; Rats; Rats, Inbred Strains; Renin - blood; Rubidium - metabolism; Sodium Chloride - pharmacology
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.HYP.15.2_Suppl.I144

Our earlier studies of cataracts in Dahl salt-sensitive (DS) rats suggested the possibility of altered lens ion transport as a contributing factor in cataractogenesis in this genetic model. We also observed that those weanling DS rats with the greatest pressor response to a high salt diet eventually developed cataracts, and that changes in salt intake modified cataract formation. In the present studies, we measured lens wRb uptake as an index of sodium-potassium adenosine triphosphatase [(Na+,K+)-ATPase] activity in weanling DS rats before the development of cataracts or sustained hypertension. Additionally, plasma renin activity was measured to indirectly assess our hypothesis that the difference between cataract-prone DS rats and DS rats unlikely to develop cataracts might be a difference in degree of salt sensitivity. At the age of 4 weeks, 50 DS and 25 salt-resistant (DR) rats were given a high sodium diet for 2 weeks, at which time the rats were divided into three groups based on the systolic blood pressure response, that is, cataract-prone DS rats with systolic blood pressure equal to or greater than 155 mm Hg, DS rats unlikely to develop cataracts with systolic blood pressure less than or equal to 125 mm Hg, and DR rats. Lens and aqueous humor Na+ and K+, lens dry weight, and water content were not significantly different among the three groups of weanling rats. Plasma renin activity was lowest in cataract-prone DS rats and low in DS rats unlikely to develop cataracts when compared with values in DR rats. Lens ouabain-sensitive wRb uptake was increased in cataract-prone DS rats but not in DS rats unlikely to develop cataracts as compared with values in DR rats. Ouabain-insensitive MRb uptake was not significantly different among the three groups. The positive correlation between systolic blood pressure and lens ouabain-sensitive MRb uptake in weanling cataract-prone DS rats, and the fact that the lowest plasma renin activity was in this group suggest that salt sensitivity might be greatest among rats that eventually develop cataracts. These data also show altered lens ion transport before cataracts or sustained hypertension in cataract-prone DS rats, and raise the possibility of a generalized disturbance in passive or active ion transport as an initiating defect in cataracts associated with salt-sensitive hypertension.