In order to find a 3,4-dihydro-2H-naphtho[1,2-b]pyran-5,6-dione more potent than the naturally occurring 2,2-dimethyl derivative [beta-lapachone (10a)], we synthesized a series of analogous compounds with modifications at position 2 of the pyran ring or at positions 8 and 9 of the benzene ring. Of the compounds tested in vitro for inhibition of RNA-dependent DNA polymerase and in mice infected with Rauscher leukemia, all retained good enzyme activity. Inhibition of the reverse transcriptase activity of the 2,2-substituted derivatives 10b-e was as strong as 10a. However, only the 2-methyl-2-phenyl derivative 10e proved to be about as potent as the 2,2-dimethyl reference compound 10a in prolonging the mean survival time of mice with Rauscher leukemia virus induced leukemia.

Vitellogenin mRNA present in total liver RNA was determined by hybridization with labeled DNA complementary to vitellogenin mRNA. In the liver of control chicks less than 0.0001% of total cellular RNA hybridized with the vitellogenin cDNA probe. About 6 h after a first estradiol injection (primary stimulation) a significant increase in vitellogenin mRNA was observed. The initial rate of accumulation of mRNA was approximately two molecules per minute per gene, 48 h later we measured a total of 7000 mRNA molecules per diploid genome (or 0.075% of total RNA). Secondary stimulation was initiated 3 weeks later when the concentration of vitellogenin mRNA had returned to the baseline of controls. Upon the second injection of estradiol (secondary stimulation) an immediate increase in the number of vitellogenin mRNA sequences was observed. The initial rate of accumulation of mRNA was approximately six molecules per minute per gene, reaching 48 h later a total of 14000 mRNA molecules per diploid genome (or 0.128% of total cellular RNA). The relative rate of vitellogenin synthesis in vivo was studied by pulse labeling and radioimmunochemical techniques. During the primary stimulation the rate of vitellogenin synthesis in vivo parallels the increase in vitellogenin mRNA concentration and 48 h later vitellogenin represented about 9% of the newly synthesized liver proteins. During the secondary stimulation the rate of vitellogenin synthesis increased first slowly during the first 6 h and then it ran parallel to the accumulation of vitellogenin mRNA. Two days later vitellogenin represented about 16% of the pulselabeled liver proteins.

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P-Lapachone is a naturally occurring compound that can be isolated from a number of tropical trees. It is shown to be a potent inhibitor of reverse transcriptase activity from both avian myeloblastosis virus and Rauscher murine leukaemia virus. In addition, it affects eukaryotic DNAdependent DNA polymerase-u activity; 50 % inhibition is reached in 60-min incubation time by about 8 pM P-lapachone. Enzyme activity is inhibited irrespective of the purity of the enzyme used or of the amount or type of template/primer or substrate present. The inhibitory effect of the drug is only observed in the presence of dithiothreitol. The primary site of action of P-lapachone appears to be the enzyme protein, as is also borne out by the specificity of its action. Eukaryotic DNA-dependent DNA polymerase-B, prokaryotic DNA-dependent DNA polymerase I, several other nucleic acid polymerases and some completely unrelated enzymes> are not affected. Reverse transcriptase and DNA-dependent DNA polymerase-a may be in someway related in possessing similarly exposed '-SH structures' in their active sites. P-Lapachone thus affords a novel means of studying such interrelationships and of further characterizing enzymes.

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