ALKANOL PERMEATION OF HAIRLESS MOUSE SKIN 243 Table II Summary of Permeability Coefficients of Methanol as a Function of Mouse Age and Anatomical Site P X 103 (cm/hr) + S.D. • Anatomical Location Mouse Age Overall (Days) Abdominal Dorsal Average 4 1.0 ñ 0.1(3) 2.7 ñ 0.3(4) 1.8 ñ 0.1 5 1.2(2) 3.5(2) 2.3 ñ 0.3 20 2.6 ñ 1.0(4) 4.3 --- 0.9(4) 3.3 ñ 0.2 25 3.4 ñ 0.3(5) 6.8 ñ 0.9(5) 5.1 ñ 0.5 39 2.5(1) b 2.3(1) b 2.4 41 2.2 ñ 0.5(4) • 2.5 ñ 0.6(4) • 2.4 ñ 0.6 42 2.9(2) • 3.3(2) • 3.1 ñ 0.5 44 2.4(1) b - - 45 2.4(2) • 2.9(2) • 2.7 ñ 0.0 46 2.6 ñ 0.2(4) • 1.9 ñ 0.5(4) • 2.3 ñ 0.3 47 2.7 ñ 10.(5) b - - 53 2.2 ñ 0.5(15) • - - 57 1.6 ñ 0.3(4) • 2.2 _+ 1.1(20) • 1.9 ñ 0.7 59 2.0 ñ 0.7(20) • 2.3 ñ 1.0(20) b 2.4 ñ 0.8 68 1.7 ñ 0.3(5) • - - 77 1.9 ñ 0.5(4) • 1.3 ñ 0.3(4) • 1.6 + 0.2 85 1.6 ñ 0.4(15) • - - 109 1.9 ñ 0.8(5) b - - 110 2.0 ñ 0.5(10) • - - 134 1.9 ñ 1.2(11) • - - 165 1.2 (1) • - - 210 1.0 ñ 0.3(4) • 1.4 ñ 0.3(4) b 1.2 ___ 0.3 270 1.3 ñ 0.3(5) 1.1 ñ 0.4(5) 1.2 ñ 0.3 360 0.8 ñ 0.2(5) 1.0 _+ 0.3(5) 0.9 ñ 0.2 Numbers in parentheses indicate numbers of animals used. From reference 15 and other works. and the dorsal skins in Figure 5. x-values appear constant between the ages of 53 and 360 days. However, there may be a slight irregularity in the x-values during the hair cycle. Such irregularity is consistent with other evidence which shows the skin functions differently as a transport barrier during the period of dynamic follicular activity. The exact placements of the homolog profiles on the log P axis differ for the different aged skins but all curOes evidence a stereotypical sigmoidal shape. This general pattern is a physicochemical expression of a barrier system in which the permeation of solutes is controlled by three different, interactive events, each with different sensitivity to chemical structure. Water and the two most polar alcohols, methanol and ethanol, permeate with comparable velocities. Since their permeability coefficients evidence no o/w-type partitioning sensitivity, one is left to conclude that these three substances are preferentially passing through some watery pores or channels within the membrane. The exponentially increasing region of the profile (moderate chain lengths) signals a shift in rate-determining pathway to a lipoidal phase in parallel with the aqueous shunt. As hydrophobicity is further increased and o/w partition coefficients become very large, permeation by way of the lipoidal regime of the stratum corneum becomes facile due to its expanding capacity. In this circumstance, aqueous strata both external to a skin

244 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table III Summary of Permeability Coefficients of Ethanol as a Function of Mouse Age and Anatomical Site P X 103 (cm/hr) + S.D. a Mouse Anatomical Location Age Overall (Days) Abdominal Dorsal Average 4 0.9 m 0.1(3) 2.4 + 0.3(4) 1.6 + 0.1 5 0.9 (2) 2.9 (2) 1.90 + 0.4 20 2.5 + 0.7(4) 4.4 + 0.9(4) 3.3 m 0.3 25 3.5 + 0.6(5) 7.5 + 1.4(5) 5.5 + 0.9 39 2.2 (1) b 2.8 (1) b 2.5 51 2.0 + 0.5(4) b 2.4 + 0.7(4) b 2.2 m 0.6 52 2.4 m 0.4(5) b _ _ 53 2.1 (2) b 2.2 (2) b 2.1 + 0.2 59 2.2 m 0.5(9) b _ _ 68 2.1 -+ 0.3(10) b - -- 77 2.4 (2) b 1.8 (2) b 2.1 + 0.4 85 1.8 + 0.4(10) b - - 102 1.3 -+ 0.3(6) - - 110 1.7 m 0.3(10) b _ _ 114 1.3 -+ 0.4(3) b - - 134 1.1 + 0.2(6) b - - 158 0.8 (2) b -- -- 210 0.9 -+ 0.2(4) 1.4 + 0.4(4) 1.2 + 0.3 270 1.2 + 0.2(5) 1.2 m 0.3(5) 1.2 + 0.2 360 0.9 + 0.1(5) 1.0 -+ 0.2(5) 0.9 -+ 0.2 Numbers in parentheses indicate numbers of animals used. From reference 15 and other works. Table IV Summary of Permeability Coefficients of Butanol as a Function of Mouse Age and Anatomical Site P X 103 (cm/hr) m S.D. • Mouse Anatomical Location Age Overall (Days) Abdominal Dorsal Average 4 3.7 m 0.3(3) 8.7 m 0.7(4) 6.1 + 0.4 5 4.2 (2) 10.6 (2) 7.4 + 0.1 20 8.7 + 2.1(4) 16.7 (2) 12.7 + 2.5 25 12.7 m 1.6(5) 23.7 + 2.5(5) 18.2 m 1.6 41 12.8 (2) b 12.7 (2) • 12.7 + 3.0 46 10.7 (2) b 8.6 (1) b 9.7 53 8.6 (2) b 8.3 (2) • 8.4 m 1.3 59 6.6 + 1.5(5) • - - 140 5.4 (2) b - - 154 5.8 (1) b - - 210 4.1 m 1.2(4) 6.2 + 1.7(4) 5.1 m 1.4 270 6.5 m 1.1(5) 6.5 m 1.7(5) 6.5 + 1.2 360 4.0 m 0.6(5) 5.1 + 1.2(5) 4.5 -+ 0.8 Numbers in parentheses indicate numbers of animals used. From reference 15 and other works.