Effect of β-3-Thienylalanine on Antibody Synthesis VII. Further Studies on the Inhibition of RNA Synthesis 1

Abstract

Spleen cells from immunized rats represent a useful model to investigate the mechanism of action of β-3-thienylalanine (β-3-TA), as inhibitor of protein synthesis and cell multiplication (1), because of the well-documented new synthesis of RNA and protein and active cell division which occurs in these cells following antigenic stimulation (2). Recent work from our laboratory has described the inhibitory effect of β-3-TA on RNA and protein synthesis in immunized rat spleen cells (1). It was shown that, after an initial lag, a small burst of RNA synthesis occurs between 24 and 36 hr following immunization; but soon the synthetic activity declines to the levels of a nonimmunized, control rat spleen. The inhibition of RNA synthesis leads to cessation of protein synthesis after a short initial attempt, and this activity declines rapidly below the level observed in controls, nonimmunized animals. The work reported here was undertaken to determine which type of RNA was affected, since a preliminary experiment in which RNA was fractionated on a sucrose density gradient indicated that radioactive label in RNA from β-3-TA-treated immunized rat spleen cells accumulated in low molecular weight oligonucleotides. The studies of Mach and Vassalli (3, 4) provided a baseline to assess the types of RNA affected by β-3-TA treatment. These authors had described a sequence of appearance of RNA of different kinds in immunized animal spleen cells. We also employed various length pulses with labeled RNA precursors to distinguish between various species of RNA (5).

The results of these experiments seem to point out that β-3-TA depresses the synthesis of an RNA which, on the basis of labeling data, may be compatible with mRNA.

Materials and Methods. Sprague-Dawley male albino rats, weighing between 250 and 300 g, were used.