Nuclear concentration of gold labeled-testosterone-bovine serum albumin conjugate injected intravenously in the hormone-target cells of rat

Abstract

We examined whether testosterone-bovine serum albumin conjugate (testosterone-BSA) showed similar distribution to radiolabeled testosterone in vivo, by injecting 2-nm colloidal gold labeled-testesterone-BSA (testosterone-BSA-gold) from rat tail vein. The testosterone-BSA-gold with the silver enhancement became visible as silver deposits under electron microscope in nuclei of Leydig cells, Sertoli cells, spermatogonia, spermatocytes and spermatids in the testis, those of the epithelial cells in the seminal vesicle and of the cardiac muscle cells in the heart of rat killed 2 h after the injection. Few deposits were present on the non-target cell nuclei in thymus and spleen. In the liver cells, the deposits were observed in the cytoplasm, but few in the nucleus. At high-power magnification without silver enhancement, the gold particles were found in the target cell nuclei in the testis. In control rat injected with BSA labeled with 2-nm colloidal gold, the percentages of nuclei showing the deposits were fewer than those in the rat injected testosterone-BSA-gold in the target cells. The deposits were also few in the nuclei of non-target cells in control rat. These results suggest that testosterone-BSA-gold is useful for morphological study of testosterone target cells, and imply that BSA conjugated with testosterone can enter the target cell nuclei of the rat.