Expression and activity of 17β-hydoxysteroid dehydrogenase type 3 in the human apocrine sweat gland

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 11670838
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Dermatology
• Research Institution: OITA MEDICAL UNIVERSITY
• Principal Investigator: TAKAYASU Susumu Oita Medical University, Dermatology, Professor, 医学部, 助手 (30284798)
• Co-Investigator(Kenkyū-buntansha): SATO Toshihiro Oita Medical University, Instructor, 医学部, 助手 (70244176) ; SONODA Tadashige Oita Medical University, Instructor, 医学部, 助手 (80244169) ; ASADA Yuji Oita Medical University, Instructor (30284798)
• Project Period (FY): 1999 – 2001
• Keywords: apocrine gland / 17β-hydroxysteroid dehydrogenase / type 3 isozyme

Research Abstract

The human apocrine sweat gland is a unique androgen target tissue which develops in adolescence both in males and females. In spite of much lower serum levels of testosterone and dihydrotestosterone in females than males, the intranuclear concentrations of these active androgens do not differ between the two sexes. 17β-Hydroxysteroid dehydrogenase (17β-HSD) type 3 is express ed in the testes and abdominal adipose tissues and has potent activity in converting androstenedione to testosterone. In the present study, we studied whether the type 3 isozyme exhists in the human apocrine gland. Freshly isolated apocrine glands from axillary skin of patients with osmidrosis were stored at -70 C. Homogenates of apocrine glands were incubated with 200 nM of ^3H-androstenedione and 1 mM of NADPH for 20 min. At neutral pH or alkaline conditions, MK 386, a type 1 5α-reductase inhibitor, was included in the mixture in order to prevent rapid consumption of the substrate by the enzyme. The following res ults were obtained. (1) Effect of cofactors : the enzyme reaction was faster in the presence of NADPH than NADPH-generating system or NADH. (2) Effect of pH : two peaks of the enzyme activities were obtained at pH 5.5 an pH 9.0. (3) Subcellular localization of the enzyme activity : the highest activity was observed in the cytosol fraction at both pH 5.0 and 9.0, although it was lower than the activity of homogenates. Other fractions such as crude nuclear, mitochondrial and microsomal fractions exhibited lesser activities. The results differ from the localization of the type 3 isozyme which localizes in the microsomal fraction. However, they are consistent with the previous report by Hodgins et al. who also found the presence of the major activity in the cytosol. (4) mRNA expression of the type 3 isozyme by RT-PCR : type 3 expression was detected at 35 cycles in the homogemate of the apocrine gland and cultured fibroblasts derived from the connective tissue surrounding the gland (the isolated apocrine gland contained a small amount of connecive tissues). Thus, although human apocrine glands express mRNA of 17β- HSD type 3 and actively converts androstenedione to testosteron at pH 5.0 like the type 3 isozyme, subcellular localization is different from that of this isozyme. Further studies are required to check whether the subcellular fractionation in our experiment was successful. In addition, the possibility of the presence of a new class of the isozyme must be investigated.