Localization of Beta-2-Microglobulin in Prostatic Corpora amylacea of Prostatic Hypertrophy Patients

Kosaku Nitta, MD, Department of Medicine, Kidney Center, Tokyo Women’s Medical College, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162 (Japan) Dear Sir, Prostatic corpora amylacea, also known as prostatic concretions, corpora colloidea, or amyloid bodies, were noted in the earliest studies of the prostatic gland [1,2]. The few reports specifically on prostatic amyloid, demonstrated by Congo red staining [3, 4], variously state that corpora amylacea, which often stain spectacularly, were not considered significant or they were ignored altogether. We therefore attempted to characterize the nature of prostatic corpora amylacea in patients with prostatic hypertrophy using immunohistochemical and immunoblot methods. Surgical prostatic resection specimens in which typical corpora amylacea lay within the prostatic glandular lumina were used in the present study. There were 12 transure-thral resection and 2 open prostatectomy specimens. Most of the corpora amylacea were Congo-red positive, and gave bifrin-gence with crossed polarising filters. Indirect immunofiuorescence of frozen sections (2 μm) demonstrated positive staining for ß2-microglobulin (ß2-MG, Dakopatts, Denmark) in the corpora amylacea (fig. 1). The corpora were also consistently immunohisto-chemically positive for amyloid P component and lysozymes, but negative for amyloid A and B, prealbumin, k and λ light chains and cytokeratin. We further examined the biochemical nature of the prostatic corpora amylacea in the prostatectomy specimens of 2 prostatic hypertrophy patients (patients 1 and 2) using immunoblot analyFig. 1. Prostatic corpora amylacea staining positive for ß2-MG in frozen sections from a prostatic hypertrophy patient by indirect immunofiuorescence. × 150. Fig. 2. Immunoblot analysis of water-soluble proteins extracted from the prostatectomy specimens of 2 prostatic hypertrophy patients. Proteins fractionated by 12.5% SDS-PAGE were transferred to nitrocellulose filters and immunodetection was performed using antihuman ß2-MG antibody. Lane 1 = Patient 1; lane 2 = patient 2. sis. The specimens were homogenized in distilled water and sedimented at 15,000 rpm for 20 min at 4 o C in a microcentrifuge. Proteins in the supernatant were fractionated by 12.5% sodium dodecyl sulfate-polyacryl-amide gel electrophoresis (SDS-PAGE),