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The present study proved that TGF-beta 1 significantly inhibited the growth of K 562 cells. The drop in cell numbers after 24 h incubation with increasing concentrations of TGF-beta 1 (0.01, 0.1, 1.0, 10.0 ng/ml) was accompanied by significant suppression of the activity of two key enzymes of polyamine biosynthesis: ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC). In contrast to ODC and SAMDC activity, TGF-beta 1 did not significantly affect the absolute concentration of spermidine and spermine in K 562 cells. We suppose that the lack of an evident drop in concentration of spermidine and spermine in spite of a significant decrease in ODC and SAMDC activity in K 562 cells exposed to TGF-beta 1 resulted from the uptake of polyamines from the extracellular space.

Summary Eight calves (males, Black and White crossbred with Holstein‐Fresian) were fed milk and milk replacer without (control group) or with potassium orotate (3 mmol./l.) supplementation for 6 weeks after birth. Orotate depressed the biosynthesis of polyamines in mucosa of the gastrointestinal tract (rumen, omasum, abomasum, colon) by decreasing of ornithine decarboxylase activity with a simultaneous compensatory increase of S‐adenosyl‐methionine decarboxylase activity. A lower concentration of spermidine and spermine in the mucosa of the colon was also noted. The above changes were accompanied by increased urinary excretion of ornithine and arginine. Calf adaptation to a high OA intake was associated with an increased activity of the OA metabolizing enzyme complex (orotate phosphoribosyl transferase and orotidine monophosphate decarboxylase) in the liver, while urinary OA losses diminished with age. Increased concentrations of uracil and uridine in the liver and higher urinary excretion of pseudouridine in OA‐fed calves was also observed. Stimulation of pyrimidine metabolism by OA depressed purine synthesis, which was reflected by a decrease of urate, hypoxanthine, and xanthine concentration in the liver. Interestingly OA enhanced urate excretion by the kidneys. OA strongly affected lipid metabolism in calves because total cholesterol, LDL‐, and HDL‐cholesterol, and triglycerides in blood plasma decreased while triglycerides accumulated in the liver of OA‐fed calves. Milk OA in concentrations characteristic of cows with hereditary orotic aciduria exerts an unfavourable effect on the metabolism of polyamines, purines, and lipids in calf tissues.

Summary Amniotic and allantoic fluids, as well as afferent lymph (tissue fluid), stimulated DNA synthesis in bovine fetal myoblasts (BFM) at low concentrations (5%). Higher doses abolished the mitostimulatory effect of these fluids and led toward inhibition of [3H]mTdR incorporation into DNA. These effects were much more evident (particularly in the case of amniotic fluid) when fluids were lyophylized prior to the experiment. BFM protein synthesis was accelerated by lymph in a dose dependent manner.