Production and secretion of interleukin-1α proteins by rat testis

Abstract The present study characterizes constitutively expressed rat testicular interleukin-1α (IL-1α) proteins. IL-1 bioactivity of crude testis protein was completely neutralized by IL-1α antiserum, IL-1 receptor antagonist, and soluble type I IL-1 receptor. Upon non-denaturating gel permeation chromatography, bioactive IL-1 eluted at molecular sizes of 45, 31, and 17 kDa and at charges of pH 5.7 and 6.0 after chromatofocusing. SDS–PAGE/Western blot analysis of proteins extracted from whole testis, seminiferous tubules, interstitial, and seminiferous tubule fluids all demonstrated IL-1α immunoreactivity at 45, 24, and 19 kDa. Activated macrophages and tissue proteins from endotoxin treated rats showed immunoreactive 31 and 19 kDa IL-1α. The results indicate that the testis produces three isoforms of IL-1α proteins that are secreted into the interstitial compartment and tubular lumen where they may exert paracrine functions. The testicular IL-1α isoforms may represent posttranslationally modified precursor, mature IL-1α, and a 24-kDa alternate splice form.