Effect of acute ethanolic intoxication on the neuraminidase activity of rat liver Golgi apparatus

Neuroexcitatory actions of Tamiflu and its carboxylate metabolite

Oseltamivir (Tamiflu) is now being stockpiled by several governments as a first line treatment for an anticipated outbreak of avian influenza caused by H5N1. However, abnormal behaviors and death associated with the use of Tamiflu have developed into a major issue in Japan where Tamiflu is often prescribed for seasonal influenza. Thus, it is critical to determine neuropsychiatric effects of oseltamivir and to establish methods for safe administration. Using juvenile rats and rat hippocampal slices, we investigated whether oseltamivir has adverse effects on the central nervous system. Systemic injection of oseltamivir (50mg/kg i.p.) produced no change in behavior within 2h. However, prior injection of oseltamivir significantly altered the duration of loss of lightning reflex following ethanol injection (3.3g/kg, i.p.). Ethanol injection in the presence of oseltamivir also resulted in enhanced hypothermia. In the CA1 region of hippocampal slices, oseltamivir (100 microM) induced paired-pulse facilitation in population spikes without changes in excitatory postsynaptic potentials. Similarly, 3 microM oseltamivir carboxylate, the active metabolite of oseltamivir, facilitated neuronal firing, though the facilitation did not involve GABAergic disinhibition. Moreover, oseltamivir carboxylate produced further facilitation following administration of 60mM ethanol. These findings indicate that oseltamivir has effects on the central nervous system, especially when combined with other agents.

Effect of ethanol on hepatic secretory proteins

Both acute and chronic ethanol administration inhibit the secretion of albumin and glycoproteins from the liver. Impairment of posttranslational steps of the secretory process are mainly involved in this secretory defect, although in some instances altered synthesis of the protein moiety may be a factor. Decreased secretion following ethanol administration results in the intrahepatic retention of export proteins. The secretory defect is a consequence of the metabolism of ethanol and is likely mediated via acetaldehyde, although more conclusive proof is still required. The manner by which acetaldehyde impairs the secretory process is unknown, but may be related to its high reactivity with hepatocellular proteins. The specific posttranslational steps or processes involved in the secretory defect are still unclear; however, it appears that the final steps of secretion (post-Golgi events) may be the primary site of impairment. Impaired secretion of proteins from the liver could contribute to altered levels of plasma proteins and hepatomegaly as well as to the liver injury observed in the alcoholic.

Isolation of Golgi fractions from colchicine-treated rat liver. I. Morphological and enzymic characterization

1. Three Golgi fractions, GF-1, GF-2 and GF-3, were isolated from the livers of rats pretreated with colchicine, which gave better yields of the fractions than ethanol treatment of rats. 2. Electron microscopic observation showed that GF-1 was composed mainly of secretory vesicles, GF-3 consisted predominantly of small tubules and flattened cisternae, and GF-2 was an intermediate fraction composed of secretory vesicles and cisternal elements. 3. Among these three fractions the highest activity of galactosyl transferase, marker enzyme of the Golgi complex, was found in GF-3 and the lowest activity was in GF-1, although a different distribution of the enzymes was observed in fractions obtained from ethanol-treated rat liver. 4. Enzymatic characterization of these fractions showed that no significant contamination with other subcellular components occurred in GF-1 and GF-2.