[Activation of bovine retinal rod outer segment cGMP-specific phosphodiesterase by the transducin-GTP complex in a physiologically significant range of free calcium ion concentrations].

The kinetic behavior of cGMP-specific phosphodiesterase in a totally bleached bovine retinal rod outer segment suspension was studied by the pH-metric method at high and low concentrations of free calcium ions (≈ 100 µM and 10 nM, respectively). The phosphodiesterase was activated by low GTP concentrations (about 1-2 µM) that were comparable with the concentration of G-protein transducin, its GTP-binding alpha-subunit was the intrinsic activator of photoreceptor phosphodiesterase. The results allow the suggestion that besides the earlier described system of RGS proteins, participating in the acceleration of GTP hydrolysis, rod outer segments also contain an additional Ca(2+)-dependent mechanism to inactivate so called "free transducin", i.e. active transducin that has not managed to interact with phosphodiesterase during the time, restricted by duration of photoreceptor response.

[The phosphorylation state of transducin beta-subunits].

The supposition that nucleoside diphosphate kinase is the enzyme that phosphorylates transducin beta-subunits on one of the histidine residues (His-266) has been analyzed. It stands the reason that 1) this enzyme is multifunctional and plays in particular the role of protein histidine kinase; and 2) the phosphorylated beta-subunit of transducin may activate transducin via the mechanism of transphosphorylation. Nevertheless, in our experiments, in which different forms of transducin preparations were incubated with α- and ß-isoforms of recombinant rat NDP kinase in the presence of [γ32P]ATP or [γ32P]GTP (specific activity of about 1 Ci/mmol) followed by separation of proteins by electrophoresis and-gel radio-autography, the phosphorylation of the transducin beta-subunit wasn't succeeded to be found. The negative result of our experiments most likely implies that the major part of transducin beta-subunits in the preparations has already been phosphorylated via a process that takes place in vivo.

[The role of polyene fatty acids in the development of acute inflammation in rats]. / Rol' polienovykh zhirnykh kislot v razvitii ostrogo vospaleniia u krys.

The effect of n6 and n3 polyunsaturated fatty acids (PUFA) on development of acute inflammation in rats has been studied. During 4 weeks male Wistar rats (initial weight 140-150 g) were on feed containing as lipid component 6% butter and 3% fish oil obtained from Sardinops sagax melanosticta (n3 PUFA-diet). The development of paw oedema induced by subplantar injection of dextran or carrageenan inhibited when the animals were on diet where prevailed n3 PUFA. In contrast, the state of paw oedema, caused by intraperitoneal administration of egg white was similarly high in rats given both n6 and n3 PUFA.