The Epidermal Barrier

THE EPIDERMAL BARRIER A COMPARISON BETWEEN SCROTAL AND ABDOMINAL SKIN*

J. GRAHAM SMITH, JR., M.D.,t ROBERT W. FISCHER, M.D. AND HARVEY BLANK, M.D.

The barrier to epidermal absorption and to water loss has been given much attention in recent years (1, 3, 5, 7, 5, 10). The purpose of

stretched over an aperture (equal to 1.1304 sq.

barrier or the mechanism of penetration but rather to report the differences between the functional barrier of scrotal skin and that of

enclosure was sealed with stopcock grease to the epidermal side of the unit. It detected any water vapor escaping from the epidermal surface. The

cm.) of a plastic chamber containing physiologic saline (Fig. 1) so that the dermis side faced the

this paper is not to consider the location of the saline. An electrohygrometer sensing element in an

entire unit is a closed system. Scrotum and abdominal skin were run simultaneously with two chambers. After each run, the probes were dried MATEEIAL5 AND METHODS in a desiccator, the chambers switched, and the Experiment 1: The penetrability of a topical experiment repeated in order to rule out a differ-

abdominal skin and mucous membrane.

anesthetic agent was determined using the method ence attributable to the probes. Experiment 3: The permeability of scrotal and described by Monash (6). Two per cent lidocaine base in a solvent of 45% isopropyl alcohol, 45% abdominal skin to topically applied substances in distilled water and 10% glycerin was the test ma- vitro was studied using a method similar to that of

terial. Cotton pledgets saturated with the anes- Flesch, Satanove, and Brown (4). Specimens of thetic solution were placed in continuous contact autopsy skin from abdomen and scrotum were with buccal mucous membrane, abdominal and taken from two separate patients. These were prescrotal skin. The end point was anesthesia to pinprick. The five subjects used were all white males between the ages of 20 to 30 years, without skin disease, and were trained observers. Experiment 2: Differences in diffusion of water

pared as in Experiment 2. The sheets of skin were

placed in the chambers as described previously, but without saline. Five per cent salicylic acid in lanolin was layered on the epidermal surface of each section and the sections incubated in a desicvapor through abdominal skin and scrotum in cator at 35° C. They were tested for the penetravitro were determined. Sections of autopsy skin tion of salicylic acid with dilute ferric chloride at were obtained from five different white males, be- intervals of 15, 30, 60, and 120 minutes. In every tween the ages of 55 to 72 years. Some of this skin instance, on taking the unit apart, the rim of each was used immediately; some was kept under re- specimen was tested with ferric chloride to rule out leakage around the edge of the skin. In order frigeration for as long as seven days. The skin was cut into pieces, approximately 2.5 to test the amount of inhibition to absorption concm. square. Excess fat was trimmed manually and tributed by the dermis, a slice of dermis without long protruding hairs were clipped a few inilli- epidermis was tested for absorption of salicylie meters from their bases. The skin was then acid in the same manner. Experiment 4: The barrier to penetration of the trimmed on a Stadie-Riggs microtome to remove all excess subcutaneous tissue. The sections were gas, hydrogen sulfide, was studied by exposing the epidermal side of skin prepared as in the previous * From the Department of Dermatology, experiment to the gas. The presence of hydrogen University of Miami School of Medicine, Miami sulfide was detected with lead acetate test paper 36, Florida. This work was performed during the tenure of scaled over the dermal side of the chamber with a special post-doctoral fellowship from the Na- cellulose adhesive tape. The cellulose tape also tional Institute of Arthritis and Metabolic Dis- prevented coloration of the paper due to leaks in eases (Dr. Smith) and supported in part by NIH the gas line. After eight minutes, the lead acetate Grant 2G-224 and U.S. Army Contract No. DA- paper was removed. 49-007-MD-731. Experiment 5: Five white males between the t Dr. Smith's present address: Division of Dermatology, Department of Medicine, Duke ages of 31 to 49 years had their scrotal and abUniversity Medical Center, Durham, North dominal skin stripped with cellulose adhesive Carolina. Presented at the Twenty-first Annual Meeting tape. The technic was the same in both areas and of The Society for Investigative Dermatology, was continued until glistening was evident. Experiment 6: Histologic sections were made of

Inc., Miami Beach, Florida, June 14, 1960.

337

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THE JOURNAL OF INVESTIGATIVE DERMATOLOGY

the chambers (Fig. 2). The paper sealed over scrotum is much darker than that sealed over abdomen.

Experiment 5: When stripped with cellulose adhesive tape, scrotal stratum eorneum came off

in large chunks, whereas abdominal stratum eorneum came off in fine sheets as ordinarily seen. From 1 to 5 strips were required to reach glistening on the scrotum but 15 or more were required for the abdomen (see Table III). Experiment 6: Histologically no marked differ-

ences could be seen between the epidermis of the abdominal skin and scrotum. Mucous membrane showed a decided difference, as was expected (see Fig. 3). No differences could be FIG. 1. Chamber used in experiments. The skin detected in sections of scrotum and abdomen was placed between the two plane surfaces of the chamber. Solutions or test substances were put under the polarizing microscope. The most

into the cylinder or applied to the opening in the intense double refraction occurred in the stratum under plate depending upon the experiment. eorneum due to birefringent material oriented buccal mucous membrane, scrotal and abdominal

skin taken from five patients and stained with hematoxalin and eosin, periodic acid Sehiff, orcein,

parallel to the surface plane. Below this level,

where tonofibrils are oriented in a vertical direction, birefringenee was weak. In contrast,

Mallory's and the Verhoff-Van Gieson stains. In mucous membrane showed intense birefringenee order to study the degree of birefringence of the ariisotropic fibers of the epidermis, unstained secTABLE I tions were studied under the polarizing micro- Time required to produce anesthesia with topical scope. Sections were also subjected to mieroradi2% lidocaine base (in minutes) ography (historoentgenography). EESULTS

Experiment 1: The time required to produce anesthesia to pinprick with topically applied 2% lidocaine base was never over 33.j minutes for

buceal mueosa or 7 minutes for scrotum, but never less than one hour for abdomen (see Table

Subject

1 2 3 4 5

3

2% 3% 1% 2%

Scrotum

Abdomen

5% 7%

60

65 120+ 120+ 120+

5 5 5

I). Experiment 2: The average water loss from TABLE II scrotal skin varied from 1.6 to 22.1 times as Water vapor diffusion rates (scrotum/abdomen) much as the abdominal skin with an average ratio of 7.4: 1 for nine separate experiments (see

Experiment

Table II). Experiment 3: Salieylie acid penetrated into the dermis of the scrotum within 15 minutes, as shown by the development of a purple color in the dilute ferrie chloride solution. Abdominal skin was never penetrated before two hours. Dermis alone (sliced 0.5—1 mm. in thickness) was penetrated within five minutes. Experiment 4: The difference in the penetration of hydrogen sulfide gas through scrotal and abdominal skin after 8 minutes is shown by the blackening of lead acetate paper sealed within Average

1

2 3 4 5 6 7 8

9

Scrotum/Abdomen

3.1 9.8 7.8 12.0

3.7 4.4 22.1

1.6 2.1 7.4

339

THE EPIDERMAL BARRIER

'14fr

w

FIG. 2. Lead acetate papers darkened by bydrogen sulfide gas which has penetrated interposed skin. Note that scrotal skin (top) has allowed greater darkening of the paper than abdominal sksn.

TABLE III and scrotum studied with microradiography Cellulose adhesive stripping of scrotum end abdomen

in the stratum corneum only. Sections of abdomen showed no differences in the epidermis. DIScUssION

Subjert

These observations suggest that the harrier is different on the scrotum from skin elsewhere and these differences may explain certain well-known

1

2 3 4 5

clinical observations. Just as alcohol gives a sensation of burning on the buccal mucous membrane, so do alcoholic solutions, ether and similar compounds, burn when applied to the scrotum. Recently, Blank, Sagami, Boyd, and Roth (2) have shown that fungistatic serum factors confine

Average

Number of Strips to Glistening on Srrotum

Number of Strips to Glistening on

5 3 2

20 20 20

3 1

15 15

2.8

18

Abdomen

cancer in chimney sweeps first reported in the dermatophyte infections to cornified structures 18th century by Pott (9), because the carcinogens outside the barrier. The rarity of the occurrence in soot may have penetrated to the dividing cells of superficial dermatophytic infection of the in the scrotal epidermis more readily. scrotum clinically, even in the presence of severe

infections of both groin and thigh, may be

SUMMARY

directly attributable to the diminished effectiveScrotal skin was compared physiologically and ness of the scrotal barrier, allowing the diffusion microscopically with abdominal skin: of these "anti-fungal" factors out into the stratum 1. Anesthesia to a topically applied anesthetic was much more rapidly induced on the scrotum. eorneum. 2. Water vapor loss was greater through the It is possible that defectiveness of the scrotal barrier explains the high incidence of scrotal scrotum.

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THE JOURNAL OF INVESTIGATIVE DERMATOLOGY

4

-

J

•• '•'•_•

• r--

r'. ..tf

:;';.::

a,_!

-

•-1 •C

FIG. 3. II and E stained sections of buccal mucous membrane (top), scrotum (middle), and abdominal skin (bottom). Note the similarity of scrotal and abdominal epidermis.

3. Salieylic acid penetrated the scrotum more between the epidermis of scrotal and abdominal skin were found. rapidly. 4. Hydrogen sulfide gas penetrated the scrotum It was concluded that the scrotal epidermal more rapidly. barrier is much less effective than that of ab5. Fewer strips were required to produce dominal skin in spite of no obvious histological glistening on scrotal skin. differences.

6. But, no striking histological differences

This reduction in the effectiveness of the

THE EPIDERMAL BARRIEH

scrotal barrier to percutaneous absorption probably explains: (1) why organic solvents give a sensation of burning when put on the scrotum; (2) why dermatophytic infections are uncommon

on the scrotum; and may explain (3) the high

341

taneous absorption and chemical effects of topical agents upon human skin. J. Invest. Derm., 25: 289—300, 1955.

5. Gitrisrusac, R. D.: Protection against the

Transfer of Matter through the Skin, Chapt. in The Human Integument, ed. S. Rothman, Pub. No. 54, American Association for the Advancement of Science, pp. 25—46, Wash-

incidence of scrotal cancer in chimney sweeps as reported by Pott. REFERENCES

ington, 1959. 6. MONA5H, S.: Topical anesthesia of unbroken

1. BEREN5ON, G. S. AND BuRdil, G. C.: Studies

epithelial barrier to skin penetration. J.

skin, A.M.A. Arch. Derm., 76: 752—756, 1957.

7. Monsn, S.: Location of the superficial

on diffusion of water through dead human skin: the effect of different environmental

8. MONA5H, S. AND BLANK, H.: Location and

epidermis. Amer. J. Trop. Med., 31: 843—853,

water vapor, A.M.A. Arch. Derm., 78: 710—

states and of chemical alterations of the 1951.

Invest. Derm., 29: 367—375, 1957.

re-formation of the epithelial barrier to 714, 1958.

2. BLANK, H., SA0AMI, S., BOYD, C. AND ROTH,

F. J.: The pathogenesis of superficial fun-

9. POTT, P.: Chirurgical Observations, Relative

gous infections in cultured human skin.

to the Cataract, the Polypus of the Nose, the Cancer of the Scrotum, the Different

3. BLANK, I. H.: Further observations on factors

the Toes and Feet, pp. 61—68. L. Hawes, W.

A.M.A. Arch. Derm., 72: 524—535, 1959.

which influence the water content of the

stratum corneum. J. Invest. Derm., 21

259—271, 1953.

4. Frascii, P., SATANOYE, A. AND BROWN, C. S.:

Laboratory methods for studying percu-

Kinds of Ruptures, and the Mortification of

Clark and R. Collins, London, England,

1775.

10. RoTHMAN, S.: Physiology and Biochemistry of the Skin, pp. 10—60, Chicago, The University of Chicago Press, 1954.

DISCUSSION DR. BRIAN POTTER (Chicago, Ill.): It should but the discussion of absorption through buccal not be said that there is no anatomical difference mucosa raises another point altogether. Penetrabetween scrotal and other skin. The dartos tion of substances through skin is determined in

muscle is present in the corium for one thing good part by the superficial barrier located in and I believe the elastic network is greater. the lower stratum corneum. In the oral mucous Possibly different innervation might be part of membranes it is an old axiom that stratum the reason for increased sensibility. corneum is present only where the mucosa is DR. HRRMANN PINKu5 (Detroit, Michigan):

tightly bound to underlying bone, as on the hard

What I want to say may be not quite germane, but I use the opportunity to point out species differences in skin physiology. Some years ago I tried to produce melanomas on the scrotum of C3H mice, which have a very deeply pigmented scrotal skin. I painted methylcholanthrcne on the scrotum for quite a number of weeks and never obtained any cancer, either squamous cell carcinoma or melanoma on the scrotum. However, many squamous cell carcinomas developed

palate or over the alveolar ridge. Ordinarily, then, one would not expect to find stratum corneum or a superficial barrier in the buccal mucosa. Consequently absorption through the buccal mucous membranes must depend on

on the skin around the scrotum where the

factors far different from those found in the skin. It is possible, for example, that the barrier may be located essentially at the cell membrane level.

At any rate this remains to be Worked out and provides an interesting problem for study. DR. MARION B. SULZBERGRR (New York,

carcinogen had spilled over. I had to conclude N.Y.): May I have the Chair's permission to that the scrotal skin of mice must be less pene- discuss these two papers together? (NB.: trable to the carcinogen than the rest of the skin. Stoughton, R. B., Clendennine, W. E. and Kruse, Da. STEPHEN ROTHMAN (Chicago, Ill.): The D.: Percutaneous absorption of nicotinic acid mucocutaneous junctions on the vulva and the and derivatives. J. Invest. Derm., 35: 337, 1960). anus behave like scrotal skin. Possibly the nature of the superficial barrier differs in all these places from the barrier in the skin elsewhere. DR. FREDERIcK D. MALKINSON (Chicago,

Regarding the paper and the conclusions

drawn by Dr. Stoughton and collaborators, on strictly scientific grounds one must have certain reservations. Their conclusions are based on an Ill.): I think that it is one thing to compare assumption. Namely the assumption that the absorption through abdominal and scrotal skin, fact that erythema appears after an application

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of any given substance to the skin's surface is must be considered before applying conclusions ipso facto proof that that substance actually derived from the study of one area. penetrated through the epidermis. This is still Dn. R. B. STOUGHTON (Cleveland, Ohio): In based on an assumption, although in many eases studying nicotinic acid derivatives, we worked probably a correct interpretation, which need with different body regions. One of the regions not apply to all substances or under all circum- was the palm, which was totally resistant to stances. There are other possible explanations of penetration of concentrated methyl or ethyl the sequence observed, including the possibility that something which is derived from the application of this substance to the epithelium, some "intermediate" or "intermediates", and not the

applied substance itself may be that which is

penetrating into the corium. This sort of a postulate must be made when one is judging crythema produced by ultraviolet light with

nicotinate. There arc no follicles in the palm and

this may be the reason. Then we thought the glans penis was a good area because of lack of follicles, presence of a granular layer and presumably a barrier area. We observed that the nicotinatcs went through the skin of the glans penis just about as readily as they went through

the forearm skin, even though there arc no

wavelengths which probably do not penetrate in follicles in this area. So all the answers arc not in any sufficient, biologically effective quantity into as to what the barrier factors arc. Dr. Thomas B. FITznTmcK (Boston, Mass.): the corium itself and still produce erythema. This also was the situation postulated by Victor Dr. Urabc of Kyushu University, Japan recently

Witten and collaborators (J. Invest. Dermat.

visited us and showed a series of color slides

28: 199, 1957; also Dermatologica 115: 661, 1957)

illustrating the marked differences in duration of

when studying polonium plaques that emitted experimental infection by F. fioccosm between the essentially alpha particles which they calculated skin of the scrotum and the adjacent skin of the did not penetrate the corium at all and still were thigh; there was a much more rapid spontaneous involution of the experimental infection of the strongly effective in producing erythema. Unless one demonstrates the penetration of a human scrotum than the adjacent thigh skin. substance itself into the deeper tissues (as was These findings suggest a higher indigenous antidone by MacKee, Herrmann, Baer and me, J. fungal activity in the skin of the scrotum. Lab. and Cm. Med. 28: 1642, 1943) the possiDR. J. GRAHAM SMITH, JR. (in closing): I

bility must always be considered that any would like to thank all the discusscrs. biological reaction observed after the application

of a substance to the epidermis is produced by secondary phenomena such as the production of "intermediates", substances which penetrate into the cutis, or the setting up of nerve reflexes, etc. etc.

Regarding penetration through the scrotal skin as demonstrated by J. Graham Smith and coworkers, I agree with the previous discussor that there are of course vast anatomic differences

between scrotal and other skin. I would not think important the factor of muscle being there

or even the richness of elastic fibers; but it is possible, for instance, that one would have to measure the number and calibre of the hair follicles per unit of surface area and just how they penetrate in order to find out whether they are not a factor in enhancing penetration of applied substance through the scrotal skin.

Dr. Rothman, I believe that the epidermal barrier of the labia will be defective just like

that of the scrotum, however, we have not studied this.

Dr. Potter, the microscopic studies were primarily focused on the outermost layers of the

epidermis. There arc well-defined differences

between the scrotal and abdominal dermis, however, since the barrier is in the epidermis, we concentrated on the epidermis seeking a morphologic explanation here for the observed differences in absorption.

In some of our experiments with histamine, which were not mentioned, it was found that with high concentrations of histamine (2% histamine phosphate) pcrifollicular whcaling was

developed about the same time on the scrotal skin as on the abdominal skin. This difference of

Moreover the pertinent biochemical and absorption of histamine may be related to its biophysical differences of different skin areas

water solubility.

THE EPIDERMAL BARRIER

Dr. Kligman, the stratum corneum, which

343

is different from the scrotum. It may be. I don't know of any method of accurately measuring the of the scrotum, was quite different from that thickness of stratum corneum. I would rather stripped off the abdomen. It came off the scrotum choose to think that the molecular configuration in big chunks. This does not imply that the of keratin or the structure of the stratum corneum thickness of the stratum corneum on the abdomen is different on the scrotum. came off with cellulose adhesive tape stripping

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94

linolenic acid extract. Arch. This pdf is a scanned copy UV of irradiated a printed document.

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