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Metallothionein (MT) is a low molecular mass protein inducible by heavy metals such as cadmium (Cd), zinc, and copper, and having high affiity for these metals. In the present study, we investigated the immunohistological localization of MT in the brains of rats and mice. In adult rat brain, almost no MT immunostaining was observed, whereas in adult mouse brain strong MT immunostaining was found in the ependymal cells, some glial cells, arachnoid, and pia mater. No immunostahhg was detected in neurons and endothelial cells. In younger rats (1-3 weeks old), strong MT immunostaining was observed in ependymal cells, choroid plexus epithelium, arachnoid, and pia mater. The overall MT concentration in adult mouse brain appeared higher than that of the brains of young and adult rats. When adult rats

Interleukin-6 (IL-6), a multifunctional cytokine, is induced in the acute-phase reaction following ultraviolet (UV) irradiation of humans and mice. Using IL-6-deficient (IL-6-/-) mice, we investigated the role of IL-6 in immunosuppression and inflammatory responses caused by UVB (280-320 nm) radiation. The IL-6-/- mice had a defective contact hypersensitivity (CHS) in response to the sensitizers 2,4-dinitrofluorobenzene and oxazolone. The injection of recombinant IL-6 (rIL-6) into these mice resulted in a marked recovery of the CHS. Serum IL-6 was significantly elevated by UV irradiation of wild-type B6 J/129Sv (IL-6+/+) mice but was not detectable in IL-6-/- mice. Interestingly, there was no induction of serum interleukin-10 (IL-10) by UV irradiation of IL-6-/- mice, whereas UV exposure caused a significant increase in serum IL-10 levels in IL-6+/+ mice. Injection of rIL-6 into IL-6-/- mice increased IL-10 to levels similar to those of IL-6+/+ mice. Being different from IL-6+/+ mice, no epidermal proliferation was found at 48 hr in the IL-6-/- mice, but delayed cell proliferation was observed at 72 hr after UV exposure. Immunohistochemical analysis demonstrated that the epidermis was capable of synthesizing IL-6 at 72 hr after UV irradiation of IL-6+/+ mice. In addition, the IL-6-positive cells appeared to be Langerhans' cells, which were detected with dendritic cell-reactive S-100 antibody. The present study strongly suggests that IL-6 may play a crucial role in the alteration of cutaneous immune responses following UV exposure, and provides evidence that IL-6 is a potent inducer of IL-10. Furthermore, IL-6 production induced by UV radiation appears to be an important early signal for repair of UV-caused skin damage.

We studied the immunohistological localization of metallothionein (MT), a low molecular weight metal binding protein, in male rat genital organs (testis, epididymis, ejaculatory duct, seminal vesicle, coagulating gland, and prostate) by use of the avidin-biotin-peroxidase complex method. MT concentrations in testis, seminal vesicle, and prostate ranged from 15-30 micrograms/g tissue. In testis, seminiferous tubules with mature spermatozoa exhibited weak MT staining, whereas the tubules containing differentiating spermatogenic cells but not containing spermatozoa showed strong MT staining. No MT immunostaining was observed in Leydig cells. In growing rat testes, the pattern of MT immunostaining was found to change with development: MT was found in supporting cells only on Day 7, spermatogonia adjacent to basement membrane on Day 14, and spermatocytes localized in the central part of the tubules on Day 21. Strong MT immunostaining in the basal cells was a common feature in other genital tissues, except the ductus efferentes. In prostate, the strongest MT staining was found in the lateral lobe, and MT was localized in apocrine secretions in the dorsal lobe. The present results suggest a close association of MT with cell proliferation and differentiation, as well as possible involvement of MT in supply or storage of zinc ions.

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