CELL RESPONSE OF RAT LIVER PARENCHYMA TO THE INFECTION BY THE INTESTINAL PROTOZOAN PATHOGEN
CRYPTOSPORIDIUM PARVUM (SPOROZOA, COCCIDIA)
N. V. Sidorenko, N. Yu. Filimonov, O. V. Anatskaya, N. V. Svezhova,1 T. V. Beyer
Institute of Cytology RAS, St. Petersburg, Russia;
1 e-mail: nad@NS4489.spb.edu
In the present work, the authors' previous studies of a "distant action", exerted by an intestinal pathogen
(Cryptosporidium parvum) on the liver of experimentally infected baby rats, were extended to include shifts in the quantity of
glycogen, protein and nuclear DNA in the host liver at different degrees of infection. One of the outcomes of this work is the discovery of a
very quick response of hepatocytes and a high sensitivity of rat liver to parasitic invasion even at a weak intensity of infection. 85-90 h after
oocyst feeding to rats, glycogen quantity in their livers was 2.5 times lower that in the control. This suggests that the infected host liver
worked under energetic starvation conditions. The proposed coefficients of general infection (I) and infection with intra-cellular
stages (F) made it possible to distinguish between the total abundance of parasites in the host intestine during the whole period
of infection, and the number of feeding intracellular stages available by the moment of autopsy. The glycogen amount in rat hepatocytes
does not depend on I, and negatively correlates with F. Unlike, the protein content in hepatocytes positively correlates
with I, being independent of F. Despite the obvious deficiency of amino acids in the infected rats, as a consequence of c
ryptosporidiosis-induced malabsorption, the protein synthesis in their hepatocytes was not at all inhibited but, on the contrary, much
activated. This is a most characteristic feature of the distant action of C. parvum on the liver of parasitized host. With C. parvum
infection, the share of polyploid hepatocytes does not correlate with either I, or F. However, compared to the control, the mean
values of relative numbers of polyploid cells in weakly, moderately, and heavily infected animals (according to I values) were higher
by 20, 100 and 100 %, respectively. In hepatocyte nuclei of C. parvum infected rats, the total area of nucleoli increases almost by 30 %.
The above changes are discussed in terms of both the liver compensatory response to the existing pathology (diarrhea), and the
host-parasite relationships. Studies into the distant action of an intestinal pathogen (C. parvum) on non-intestinal organs (liver)
of the infected host may be qualified as a new and original approach to pathogenesis of protozoan infections (coccidio-ses sensu lato),
to which young host specimens are known to be most susceptible.
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