Freeze-drying allows double nonradioactive ISH and antigenic labeling

Because tissue freeze-drying is an excellent way to preserve antigenic conf ormation, we have tested the feasibility of this technique to reveal nonrad ioactive in situ hybridization (ISH) of tissue mRNA. We have compared mRNA detection after different methods of tissue preservation, freeze-drying, cr yosectioning, and formaldehyde or methanol fixation. Our results show that nonradioactive ISM is more sensitive for tissues preserved by freeze-drying than for other tissue preparations. We have demonstrated that freeze-dryin g allows combination of ISM and immunohistochemistry for simultaneous detec tion of mRNA and antigen because with this technique of tissue preservation ISM does not affect the sensitivity or the amount of the detected antigens . This work underscores the fact that tissue freeze-drying is an easy, conv enient, and reliable technique for both ISM and immunohistochemistry and ac hieves excellent structural conditions for nonradioactive detection.