Lenticular rubidium uptake in hypertensive `cataract-prone' salt-sensitive rats

We have previously reported a high incidence of cataract formation in adult hypertensive salt-sensitive rats, suggesting that hypertension may be an important cataractogenic risk factor. Weanling salt-sensitive rats that eventually developed cataracts showed a marked increase in the pressor response to a high-sodium diet compared to salt-sensitive rats that did not develop cataracts. A lens and aqueous fluid electrolyte imbalance occurred in all adult salt-sensitive rats examined, but was greater in the salt-sensitive rats that developed cataracts, suggesting an alteration in lens and/or ciliary ion transport in cataracts associated with hypertension. In the present study, lens Rb uptake was measured in adult hypertensive salt-sensitive rats prior to cataract formation. `Cataract-prone' salt-sensitive hypertensive rats (increased pressor response to a high sodium diet given at weanling age), salt-sensitive hypertensive rats unlikely to develop cataracts and control salt-resistant rats were studied at the age of 16 weeks. Total and ouabain-insensitive lens Rb uptake were measured for the determination of ouabain-sensitive uptake, an index of Na,K-ATPase activity. Lens oaubain-sensitive Rb uptake was low in adult hypertensive cataract-prone salt-sensitive rats before cataract formation compared with values in control resistant rats. Intermediate values were observed in hypertensive salt-sensitive rats unlikely to develop cataracts. These data suggest that altered ion transport may play a pivotal role in cataractogenesis associated with this model of hypertension. The data are also consistent with the concept of a generalized defect in epithelial ion transport, at least in salt-sensitive hypertension.