Atubular glomeruli in lithium-induced chronic nephropathy in rats

Chronic renal failure was induced by administering lithium orally to 14 newborn rats. Seven rats were treated for 8 weeks followed by 8 weeks without lithium (group Li/C) and seven for 16 weeks (group Li/Li). Plasma urea and renal concentrating ability were measured, and one kidney fixed by vascular perfusion. Mean glomerular volume as well as volumes of individual glomeruli were estimated. In addition, the structural integrity between the glomerulus and the proximal tubule was investigated on serial sections. No sclerotic glomeruli were present. Only 37.6 and 27.9% of the glomeruli in the Li/C and Li/Li groups, respectively, were connected to a normal proximal tubule, and most remaining glomeruli were atubular. The mean glomerular volume was unchanged in the Li/C group and reduced by 40% in the Li/Li group. The intraindividual variation in glomerular volume was about 10-fold larger in the lithium-treated groups than in controls. The glomeruli connected to normal proximal tubules had the largest volumes, and hypertrophied glomeruli were encountered more frequently in the Li/C group than in the Li/Li group. There was a significant positive correlation between the plasma urea and the fraction of glomeruli that were not connected to normal proximal tubules. We previously demonstrated in this lithium model that there is a significant correlation between the tubulointerstitial lesion and the impairment of renal function. However, with the demonstration of atubular glomeruli we have a new explanation for the reduction in renal function in this model.