The retinal capillaries of the rat in deoxycorticosterone hypertension. An ultrastructural study with the diffusion tracer lanthanum.

Unilaterally nephrectomized rats treated with deoxycorticosterone and 1% sodium chloride in their drinking water developed severe systemic hypertension with marked cardiac and renal lesions. No pathologic changes could be detected in the retinal vasculature by light microscopy, but electron microscopy revealed inconstant alterations in the pericytes of retinal capillaries: these cells showed hyaloplasmic edema, margination of chromatin, dilatation of rough endoplasmic reticulum, and swelling of mitochondria. Injection of lanthanum into control rats confirmed that this 40-A tracer cannot pass the interendothelial tight junctions. In hypertensive animals, however, it penetrated these junctions and could be visualized in capillary basement membranes and between cells of the retina. The results indicate that an increase in permeability is probably the first pathologic change to occur in the retinal capillaries of hypertensive rats.