Choroid Plexus, Brain and Heart Natriuretic Peptide Development in Space

Neurophysiology

Rattus norvegicus (Sprague-Dawley rat)
Flight: 10 dams, 10 fetuses, 10 pups Female (dams), Male and Female (fetuses and pups)

Synchronous: 10 Dams, 10 Pups, 10 Fetuses; Vivarium: 10 Dams, 10 Pups, 10 Fetuses

Ambient Temperature Recorder, Animal Enclosure Module

The aims of the studies were: 1) to investigate the choroidal alterations induced by 11 days of development in space in developing rats and pups, and to compare results obtained in adult rats flown during the SLS-2 experiments with the ultrastructural and immunocytochemical observations obtained from dams dissected 2 days after landing from an 11-day space flight; and 2) to evaluate qualitative or quantitative changes in storage and biosynthesis of natriuretic peptides in cardiac tissues in rats that developed for 11 days in space and in the dams that delivered 2 days after landing.

Brains from dams, fetuses, and pups were removed after decapitation. Choroid plexuses were dissected either 3–4 hours or 2 days after landing. Samples were fixed and embedded in LX-112 epoxy resin or in 3% paraformaldehyde in PBS. The hypothalamus and remaining brain with brainstem from the same brains were removed and frozen until sectioning and observation. Whole brains from two additional animals in each group were prepared and embedded in Paraplast. Four other whole brains were frozen and stored at 80 °C. Hearts were similarly processed for electron microscopy, immunocytochemistry. Atrial and ventricle samples were frozen to be studied by radioimmunoassay, in situ hybridization and competitive RT-PCR.

In dams, a strong restoration of the cell polarity and a restored choroidal protein expression was observed. These results suggested that after 2 days of readaptation to Earth gravity, choroidal functions were restored, indicating that secretory processes were re-established early after landing. In fetuses and pups, maturation of choroid plexuses appeared slightly delayed, in comparison with fetuses and pups developed on Earth. Results on the expression of natriuretic peptides in heart showed that cardiac atrial natriuretic peptide (ANP) biosynthesis of flight dams was increased by about twice, when compared to synchronous and vivarium control rats. Rat fetuses developed in space displayed an altered maturation of cardiac ANP, whereas the cardiac ANP storage was slightly reduced in both flight and synchronous control groups, compared to vivarium control rats. This suggested that ANP metabolism during development is impacted by both the microgravity environment and the housing conditions.

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Davet, J. et al.: Cardiac Atrial Natriuretic Peptide (ANP) in Rat Dams and Fetuses Developed in Space (NIH-R1 and NIH-R2 Experiments). Life Sciences, vol. 64(17), 1999, pp. 1533–1541.

Davet, J. et al.: NIH-R1 Mission: Effects of a 11-Day Spaceflight on Rat Brain and Heart Natriuretic System in Fetuses, Pups and Dams (abstract). American Society for Gravitational and Space Biology Bulletin, vol. 9(1), Oct 1995, p. 84.

Gabrion, J. et al.: NIH-R1 Mission: Effects of a 11-Day Spaceflight on the Fetal Development of Choroidal Plexus in Rats (abstract). American Society for Gravitational and Space Biology Bulletin, vol. 9(1), Oct 1995, p. 96.

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