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GOMORI'S METHOD FOR URATES
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FIXATION: 95% or absolute alcohol.
TECHNIQUE: Paraffin sections cut at 5 µm.
SOLUTIONS:
5% Silver Nitrate Solution
Silver nitrate ---------------------------------------------------------------------- 1.0 gm
Distilled water -------------------------------------------------------------------- 20.0 ml
3% Methenamine Solution
Hexamethylenetramine (methenamine) ------------------------------------------- 12.0 gm
Distilled water ------------------------------------------------------------------- 375.0 ml
Ethylene glycol ------------------------------------------------------------------ 25.0 ml
Methenamine-Silver Nitrate Solution (Stock)
Silver nitrate, 5% solution ------------------------------------------------------- 20.0 ml
Methenamine, 3% solution ------------------------------------------------------ 400.0 ml
This solution is good for about one month if stored in a refrigerator.
3% Sodium Borate Solution
Sodium borate decahydrate ----------------------------------------------------- 3.0 gm
Distilled water ------------------------------------------------------------------ 100.0 ml
Methenamine-Silver Nitrate Solution (Working)
Methenamine-silver nitrate solution (stock) -------------------------------------- 20.0 ml
Distilled water ------------------------------------------------------------------ 20.0 ml
Sodium borate, 3% solution ---------------------------------------------------- 2.0 ml
Prepare fresh.
2% Sodium Thiosulfate Solution
Sodium thiosulfate --------------------------------------------------------------- 2.0 gm
Distilled water ------------------------------------------------------------------- 100.0 ml
0.2% Fast Green Solution (Stock)
Fast green FCF, C.I. 42053 ----------------------------------------------------- 0.2 gm
Distilled water ------------------------------------------------------------------- 100.0 ml
Acetic acid, glacial --------------------------------------------------------------- 0.2 gm
Fast Green Solution (Working)
Fast green (stock) ---------------------------------------------------------------- 10.0 ml
Distilled water -------------------------------------------------------------------- 35.0 ml
1. Deparaffinize and run slides to 95% alcohol. Stand slides on end and allow to
thoroughly dry.
2. Place in working methenamine-silver nitrate solution and place in a 37˚ C oven for 2 hours.
3. Rinse in four changes of distilled water.
4. Place in 2% sodium thiosulfate for 1 minute.
5. Rinse in four changes of distilled water.
6. Counterstain with working fast green solution for 30 seconds.
7. Rinse in three changes of distilled water.
8. Dehydrate in graded alcohols.
9. Clear in three or four changes of xylene.
10. Mount with synthetic resin.
Urates and uric acid ------------------------------------------------ dark brown to black
Melanin and some calcium salts ------------------------------------- black
Background --------------------------------------------------------- green
Uric acid occurs in the form of acid sodium urate. Heavy metal salts of uric acid are insoluble and can be converted into colored compounds as can phosphates and carbonates. Uric acid is an argentaffin substance and therefore can be identified by the above argentaffin method. It can also be polarized which sometimes aids in its identification.
Small amounts of calcium salts are unlikely to give false positive results because they are dissolved by the silver solution. If an additional precaution is required, the section should be treated with 0.5% hydrochloric acid in 70% alcohol for two minutes to remove all traces of calcium salts before treatment with the silver solution.
Sheehan, D.C. and Hrapchak, B.B.: Theory and Practice of Histotechnology, The C.V. Mosby Company, St. Louis, 1980, pp. 225-226.
Culling, C.F.A.: Handbook of Histopathological and Histochemical Techniques, Butterworths, London, 1974, pp. 389-390.
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