Bovine seminal ribonuclease (BS-RNase) is a dimer in which the subunits are cross-linked by disulfide bonds between Cys31 of one subunit and Cys32 of the other. Dimeric BS-RNase is resistant to ribonuclease inhibitor (RI), a protein endogenous to mammalian cells, and is toxic to a variety of cell types. Monomeric BS-RNase (like its homolog, RNase A) is bound tightly by RI and is not cytotoxic. The three-dimensional structure of the RI·RNase A complex suggests that carboxymethylation of C32S BS-RNase (to give MCM31) or C31S BS-RNase (MCM32) could diminish affinity for RI. We find that MCM31 and MCM32 are not only resistant to RI, but are also aspermatogenic to mice. In contrast to the aspermatogenic activity of dimeric BS-RNase, that of MCM31 and MCM32 is directed only at spermatogenic layers. Intratesticular injection of MCM31 or MCM32 affects neither the diameter of seminiferous tubules nor the weight of testes. Also in contrast to wild-type BS-RNase, MCM31 and MCM32 are not toxic to other cell types. Direct immunofluorescence reveals that MCM31 and MCM32 bind only to spermatogonia and primary spermatocytes. This cell specificity makes MCM31 and MCM32 of potential use in seminoma therapy and contraception.

• Publication type
• Journal Article MeSH

BACKGROUND: Bovine seminal ribonuclease (BS RNase) was determined to have a specific suppressive effect on the proliferation of T lymphocytes in vitro. Its immunosuppressive effect was proven in skin grafting in mice as well. METHODS: The immunosuppressive effect of BS RNase was evaluated in tissue cultures and on a model of corneal transplantation in rabbits. The penetration of BS RNase into the anterior chamber was detected by immunoblotting of anterior chamber fluid obtained from animals treated either topically or subconjunctivally. RESULTS: In vitro blastic transformation of mouse T lymphocytes was significantly inhibited by BS RNase (concentrations 15-250 micrograms/ml). No such effect was observed on B lymphocytes. In the rabbit model of corneal graft rejection, BS RNase injected subconjunctivally prolonged mean graft survival time significantly (33.4 days) compared with placebo (salt solution; MST 17.7 days). No BS RNase was detected by immunoblotting in anterior chamber fluid after either topical or subconjunctival application. CONCLUSION: BS RNase showed significant immunosuppressive effect both in the blastic transformation test and in the rabbit high-risk model of corneal transplantation. Negative results of anterior chamber fluid immunoblotting indicate poor absorption of the drug.

• MeSH
• Lymphocyte Activation drug effects   MeSH
• Administration, Topical MeSH
• Cell Division MeSH
• Endoribonucleases pharmacokinetics   pharmacology   MeSH
• Immunoblotting MeSH
• Immunosuppression Therapy methods   MeSH
• Injections MeSH
• Conjunctiva MeSH
• Rabbits MeSH
• Cells, Cultured MeSH
• Mice, Inbred BALB C MeSH
• Mice MeSH
• Anterior Chamber metabolism   MeSH
• Graft Survival drug effects   MeSH
• Graft Rejection immunology   metabolism   prevention & control   MeSH
• Cattle MeSH
• T-Lymphocytes drug effects   immunology   MeSH
• Corneal Transplantation * immunology   pathology   MeSH
• Animals MeSH
• Check Tag
• Rabbits MeSH
• Male MeSH
• Mice MeSH
• Cattle MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Endoribonucleases MeSH
• ribonuclease SPL MeSH Browser