Aim To study the effect of tetrandrine derivative HL-49 on the conformation and biological ac-tivity of Bloom helicase ( BLM ) , and to explore its antitumor mechanism.Methods The effect of HL-49 on the conformation of BLM helicase was studied by ultra- violet spectroscopy.The effects of HL-49 on DNA binding activity, DNA chain dissociation activity and ATPase activity of HL-49 on BLM DNA helicase were analyzed by fluorescence polarization and malachite green-ammonium phosphomolybdate colorimetric method.Results HL-49, a tetrandrine derivative, indirectly inhibited the ATPase activity of BLM DNA heli- case and DNA unwinding activity by reversible binding with DNA.The results of fluorescence polarization experiments showed that HL-49 could not affect the bind ing activity of BLM DNA helicase to DNA (dsDNA/ss- DNA) , but could bind to DNA in a concentration-de- pendent manner (P < 0.01).With the increase of HL- 49 concentration, the DNA unwinding ability of BLM DNA helicase decreased, and the Kobs value decreased gradually.The results of malachite green-ammonium phosphomolybdate colorimetry showed that HL-49 could significantly inhibit the ATPase activity of BLM DNA helicase.Conclusions HL49 can inhibit the ATPase activity and DNA unwinding activity of BLM DNA helicase by the reversible binding with DNA.

OBJECTIVETo explore the effects of proadrenomedullin N-terminal 20 peptide (PAMP) on nitric oxide (NO) production in rat cardiac fibroblasts (CFs) induced by angiotensin II (AngII) stimulation.

METHODSNeonatal SD rat CFs isolated by trypsin digestion were cultured and stimulated with PAMP, AngII or their combination, and NO production in the CFs in response to the treatments was measured by nitric acid reductase method.

RESULTSNO levels in the cell culture treated with 1x10(-9), 1x10(-8), 1x10(-7), and 1x10(-6) micromol/L AngII were 73.88-/+2.23, 64.34-/+3.02, 54.12-/+2.82, and 40.21-/+1.45 micromol/L, respectively, showing significant differences between the groups (P<0.01), whereas treatment of the cells with 1x10(-9), 1x10(-8), 1x10(-7), and 1x10(-6) micromol/L PAMP did not result in significant variation in NO production (74.40-/+3.42, 74.91-/+2.66, 75.77-/+3.31, and 74.23-/+2.43 micromol/L, respectively) in comparison with that of the blank control group (74.57-/+2.49 micromol/L, P>0.05). Combined treatments with 1x10(-7) micromol/L AngII and PAMP at 1x10(-9), 1x10(-8), 1x10(-7), and 1x10(-6) micromol/L PAMP caused significant increment of NO production (66.15-/+2.95, 80.58-/+3.77, 88.67-/+1.46, and 96.22-/+2.96 micromol/L, respectively, P<0.01) in a PAMP dose-dependent manner, suggesting the abolishment of AngII-induced enhancement of NO production in the CFs by PAMP.

CONCLUSIONPAMP increases NO production in the CFs in the presence of AngII but it does not induce significant changes in NO production when used alone.

Adrenomedullin ; Angiotensin II ; pharmacology ; Animals ; Animals, Newborn ; Cells, Cultured ; Fibroblasts ; cytology ; drug effects ; metabolism ; Myocytes, Cardiac ; cytology ; drug effects ; metabolism ; Nitric Oxide ; biosynthesis ; Peptide Fragments ; pharmacology ; Protein Precursors ; chemistry ; pharmacology ; Proteins ; chemistry ; pharmacology ; Rats ; Rats, Sprague-Dawley