Representative Pizzolato staining of paraffin embedded kidney sections of Hydroxy-L-Proline (HLP) treated rats.

(A) Light micrograph section showing little calcium oxalate crystal depositions shown with single arrows at 10X. (B) Light micrograph section of the kidney showing brownish-black stained calcium oxalate crystal depositions shown with single arrows with the oral administration of 5% hydroxy-l-proline (10X). Majority of the crystals were seen in the tubular lumens of the distal tubules and collecting ducts of the cortex and outer medulla. There were no crystal deposits in normal rat kidneys.