Pharmacological responsiveness of the myoepithelium of the isolated human axillary apocrine sweat gland

SUMMARY Human axillary apocrine glands are endowed with well developed myoepithelium, but its pharmacological responsiveness has remained unknown. The present study is part of our efforts in determining the role(s) played by exocrine myoepithelium in the overall secretory processes. Single human apocrine glands were isolated from biopsy skin specimens and were stimulated with various pharmacological agents in vitro . Tubular contraction was recorded photomicrographically and was interpreted as being due to myoepithelial contraction. The tubular contraction was induced by stimulation with phenylephrine (5 × 10 −6 M) or adrenaline (5 × 10 −6 M) but not with isoproterenol (5 × 10 −6 M) or acetylcholine (5 × 10 −6 M). A higher concentration of acetylcholine (10 −4 M) produced a minor degree of contraction. The phenylephrine‐induced contraction was blocked by phentolamine (10 −5 M) or by EGTA (5 mM) but not by propranolol (10 −5 M) or by atropine (10 −5 M). It was concluded that the contractile response of the apocrine myoepithelium is selectively controlled by the alpha‐adrenergic stimulation. The possibility is discussed that the major function of the apocrine myoepithelium is not just the pumping out of the preformed sweat but is, as in the eccrine sweat gland myoepithelium, the provision of structural support for the apocrine secretory epithelium to withstand the increase, if any, in the luminal hydrostatic pressure during apocrine sweat secretion.