Ageing of Skin

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Abstract
Titration curves of skin were determined by measuring the density of colloidal charge of finger epidermis in solutions of pH varied between 2.2 and 7.4. A group of 36 subjects aged 5 to 95 was studied. The effects of lipid extraction and of various chemical reagents were observed in some of the subjects. In the growth period (age 5 to 20), the characteristic change was an increase of both acid and base -binding capacities of the skin accompanying a moderate increase of the isoelectric point to the adult level of pH 4.6. After age 20, the acid and base combining properties of the skin showed little change until about age 60. After the age of 70 there were decreases in acid-binding at pH 2.2, and in the density of groups dissociating between pH 2.2 and 5.0. These decreases were approximately proportional. Base-binding capacity at pH 7.4 showed no tendency to decrease. The isoelectric point became greater than pH 5 after age 80. From physiochemical and morphological con- siderations the changes in the titration curves are related to senescent diminution of keratin formation. Decreases of acid-binding and of titratable groups below pH 5 are shown to be of the same relative order of magnitude indicated by independent measurements of keratin formation.

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