[Studies on the specific effects of serum and cytoplasm of the liver on the [3H]TTP-incorporation of isolated liver nuclei (author's transl)].

Previous authors have described that liver cytoplasm and serum from partially hepatectomized rats stimulate the DNA synthesis of isolated nuclei of liver cells. The aim of our investigation was to prove whether such stimulating effects are part of a specific regulation of growth. The sera and the cytoplasm supernatant 105000 x g) were isolated at several intervals after partial hepatectomy and laparotomy and were tested on isolated nuclei of liver cells from adult rats partially hepatectomized 20 hours before. The supernatants isolated at 8 and 16 hours after both partial hepatectomy and laparotomy have a significant stimulatory effect on the [3H]TTP-uptake by nuclei. The presence of serum (10%) causes a general elevation (75%) of the [3H]TTP-uptake by isolated nuclei. The sera isolated 4 to 12 hours after operation from both partially hepatectomized and laparotomized rats have an additional stimulatory effect on the [3H]TTP-uptake synthes of nuclei. In no case did the sera and liver cytoplasm of partially hepatectomized rats have a significantly different and therefore "specific" effect on the nuclear DNA synthesis. Additional experiments showed that frozen and thawed nuclei of liver cells respond only to the nutritive power but not to the stimulatory effects of the sera. Thus, thawed nuclei cannot be used for growth investigations.