Irritant actions of unphysiological pH values. A controlled procedure to test for topical irritancy
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The abdominal skin of juvenile white mice was used. Topical application was accomplished by intracutaneou injection. The solutions tested were thoroughly standardized. By using a special buffer system, a mixture of histidine glutamate and lysine glutamate, each pH value could be tested with the same buffer capacity. The pH values varied from pH 3 to pH 11, the solutions being always isoosmolalic with plasma.
Two criteria were used to judge the irritancy: (a) the edematous reaction for the first 6 h and (b) the macroscopic aspect after 24 h. A very special procedure enabled us to obtain objective numerical values for criterion (a).
The results disclose that irritation becomes manifest at pH 4 and pH 10, becomes clear-cut with pH 3 and even more so with pH 11, and depends strongly on the buffer capacity employed.
With two substances — amidosulfuric acid and (tri) sodium phosphate — it was exemplified how the procedure could be used to routinely screen for topical irritancy in an informative, inexpensive and decent manner.
KeywordsSodium Phosphate Glutamate Lysine Histidine
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