The Dynamics of Eccrine Sweating in Man
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector THE DYNAMICS OF ECCRINE SWEATING IN MAN I. SWEAT DELIVERY THROUGH MYOEPITHELIAL CONTRACTJON* HARRY J. HURLEY, M.D., D.SC.(MED.) AND JOSEPH A. WITKOWSKI, M.D. The functional status of the myoepithelium of30—50 microns in length which invest the secre- the human eccrine sweat gland has long been intory portion of the gland. Myoepithelial cells are question. Unlike the myoepithelium of the apo-not found about the eccrine duet. The composite erine and mammary glands whose expressiveof myoepithelial cells for a single gland is spoken action in the delivery of the secretory product toof as the myoepithelium of that gland. Each the skin surface is now established fact (1, 2), themyoepithelial cell is set within the diaphanous role of the eccrine myoepithelium has never beenbasement membrane of the tubule and is parallel clarified. The literature contains evidence sug-or nearly parallel to its neighbor, the group of gesting the participation of eccrine myoepithelialcells forming a sheet of longitudinally-oriented contraction in sweat delivery principally at lowfibrillar cells. Overall, the myoepithelium runs in rates of sweating (3, 4, 5). During profuse sweat-a slightly spiral fashion, its long axis approxi- ing, the necessity for myoepithelial contractionmating obliquely that of the tubule. is not generally admitted and delivery of sweat Some of the myoepithelial cells may be seen to to the surface is presumed to result from thebranch (fig. 1). Their nuclei are narrow and con- pressure generated from the secretory processform to the overall shape of the cells. Histologi- alone (3). cally, transection of the eccrine tubule may re- In the course of recent investigation of sweatveal the myoepithelial cells as small nipple-like gland function utilizing newly-devised technicsprojections at the base of the secretory cells. employing locally administered dyes excreted byHowever, some of the adjacent tubules usually the ecerine glands (6), we have observed certainshow myoepithelial cells cut obliquely or longi- specialized forms of localized ecerine sweatingtudinally. The myoepithelium is eosinophilic in which provide new evidence for the role of thestaining and can be especially well outlined with myoepithelium in the sweating process. These re-the phosphotungsticacid-hematoxylin and sponses indicate not only an expressive deliveryperiodic acid-Schiff technics, as well as with of sweat to the skin surface as a result of myoepi-silver stains. Glycogen is present in myoepithelial thelial contraction but suggest also that myoepi-cells in modest amounts. They are also strongly thelial contraction is involved with the process ofreactive for sulfhydryl groups and apparently ecerine sweat formation as well. contain alkaline phosphatase (7). Lipid granules, As a preamble to the presentation of our ex-thought to be phospholipids, are found in rows perimental findings, the morphologic features ofalong the long axis of the myoepithelial cells. It the myoepithelium will be reviewed. The readerhas never been clearly established whether the is referred to the excellent and detailed analysesnerves to the sweat glands terminate on the myo- by Rothman (3) and Kuno (4) of the studies inepithelial or secretory cells or supply both struc- the literature which support the statements madetures. above concerning current views of eccrine myo- Myoepithelial cells are seen in both the mam- epithelial function. mary and apocrine sweat glands and, in these glands, are larger than in the eccrine sweat glands. MORPHOLOGY OF THE MYOEPJTHELIUM Except for their smaller size, however, the eccrine The myoepithelial cells of the eccrine sweatmyoepithelial cells are fundamentally identical gland are slender, fibrillar or myoid strands someanatomically to those of the mammary and apo- crine glands. *Fromthe Section of Dermatology, Depart- ment of Medicine, Hahnemann Medical College The general consensus is that myoepithelial and Hospital, Philadelphia, Pennsylvania. cells are a variety of smooth muscle, despite their This study was supported by a research grantapparent ectodermal origin. This view is sup- from the National Cystic Fibrosis Research Foundation. ported by the fact that longitudinally-oriented Received for publication December 23, 1961.striae or fibrils similar to those of smooth muscle 329 330 THEJOURNAL OF INVESTIGATIVE DERMATOLOGY S ¾ 4 4 Ps I Fia. 1A. Human Eccrine Sweat Gland Myoepithelium (Hematoxylin and eosin). The fibrillar nature of the eccrine myoepithelial cells is apparent from the above photomicrograph. Observe the branching of one myoepithelial cell (arrow). More prominent staining of myoepithelial cells is evident after phos- photungstic acid-hematoxylin (Figure 1B). Mag. X 430. in general, are visualized in myoepithelial cellsMaterials and Methods (7, 8). It should be remembered that unlike Fifty-two healthy adult Caucasian and Negro skeletal muscle, which is histologically uniform,males, ranging in age from 20 to 51 years, were smooth muscle represents a diverse group ofused in this study. The skin of the volar forearm myoid tissues whose structure varies according towas used predominantly as the test site in these experiments, although the palm, back, axilla and the special nature of the functions each type per-anterior aspect of the legs were also examined. forms. This structural heterogeneity prevents theAll injections were made through 26 gauge absolute definition of smooth muscle on the basisneedles and the test areas visualized grossly and of anatomic criteria alone. with the aid of a stereoscopic microscope (2—401<). The studies were carried out in a well-ventilated room during all seasons of the year. The room EXPERIMENTAL STUDIES temperature never exceeded 25° C. Humidity The observations to be described were madecontrol was unnecessary since humidity variations possible by the use of newly-developed technicscould not influence these experiments. The dyes of study of sweat gland function using locally-employed were methylene blue (0.5%) and fluores- introduced dyes excreted by the sweat glands (6).cein sodium (5-10%), in physiologic or buffered These technics demand that sweat is newly-formed (phosphate buffer, pH 7.2) saline or distilled or secreted since the excreted dyes are intro-water, pyrogen-free. These dyes were introduced duced into the dermal interstitial space and mustinto the test areas by intradermal injection as be drawn into the glands when they are stimu-previously described (6), and in the case of the lated. Three forms of local stimulation of eccrinefluorescein sodium, also by percutaneous absorp- sweating were employed and will be discussedtion. The latter technic involved the initial light in turn. They are: shaving of the skin area and preparation of a 1. Tissue Distention As Sweating Stimulus "wall" of petrolatum about the test site to con- 2. Local Physical Stimulation Of Eccrinetain the fluorescein sodium which was left on the Sweating skin for 15—30 minutes. A Wood light (TJVL- 3. Special Pharmacologic Stimulants Of Bc-3600A) was used to detect the fluorescent dye in crine Sweating the sweat. Prior to the stimulation of sweating, DYNAMICS OF ECCRINE SWEATING 331 I I A p p 1.4 '4 B. Human Eccrine Sweat Gland Myoepithelium (Phosphotungstic Acid-Hematoxylin stain). Eccrine myoepithelial cells cut in longitudinal and oblique axes are shown (arrows). Coiled appearance or wave- like undulation of several of the myofibrils, possibly indicating contractile activity, is evident at m. Mag. x360. the test areas were covered with a thin film ofstained blue sweat droplets were evident within castor oil or mineral oil* to prevent evaporation3—5 seconds following the injection of the distilled and spreading of the sweat droplets. water. New droplets continued to appear over the next 15—30 seconds. The time of appearance of the 1. Tissue Distention as Sweating Stimulus initial droplets was not coincident with the dis- tention of the dermis as produced by the injection The initial experimental approach involvedbut rather just followed the "recoil" or relaxation attempts to stimulate mechanically the sweatof the tissue subsequent to its distention. Some gland myoepithelium by a distending force in theregression of the size of the droplet or actual dis- dermis. In twenty-five subjects, 0.03 cc. of 0.05%appearance of the smaller droplets could be ob- methylene blue in buffered saline was introducedserved occasionally but not regularly. The re- intradermally into the volar aspect of the forearm.sponse was superior in some subjects and was seen These areas were presumed to be free of activeto involve only the immediate test area (approxi- sweating prior to or at the time of injection ofmately 1.5 cm. in diameter) of the injection wheal dye since immediately adjacent and symmetricalplus a few satellite glands. It should be stressed skin areas were anidrotic as indicated by thethat the droplets seen with this stimulus were Wada modification of the starch-iodine colon-generally smaller than those produced by pilo- metric technic (9). In addition, in some subjectscarpine, physostigmine or thermal stimulation the immediate test area was prepared initially(fig. 2). In some instances, a few blue sweat drop- according to the Wada technic and found to belets were visible even before the injection of the free of any active sweating prior to the followingdistilled water was made. Movement of the needle test. The test area was covered with castor oilbeneath the skin without injection of fluid also and, after an interval of 2—4 minutes, 0.05 cc.would occasionally excite the appearance of a distilled water was then rapidly injected intra-few small blue sweat droplets. dermally at this site. This injection required Under high magnification (30X) and when the 2—3 seconds. response was first evident, it was often possible In all subjects it was observed that tiny, deeply-to discern the blue-stained coiled portion of the * Thelack of autofluorescence of mineral oilsweat duct. Once the sweat droplets increased in made it more desirable for use in the experimentssize, however, this was obscured.