Spaceflight affects postnatal development of the aortic wall in rats.

Shin-Ichiro Katsuda,Hidefumi Waki,Masao Yamasaki,Toshiyasu Okouchi,Kiyoaki Katahira,Tadanori Nagayama,Yukako Miyamoto,Masao Miyake,Hirotaka O-Ishi,Haruyuki Wago,Masamitsu Hasegawa,Tsuyoshi Shimizu

doi:10.1155/2014/490428

Abstract

We investigated effect of microgravity environment during spaceflight on postnatal development of the rheological properties of the aorta in rats. The neonate rats were randomly divided at 7 days of age into the spaceflight, asynchronous ground control, and vivarium control groups (8 pups for one dam). The spaceflight group rats at 9 days of age were exposed to microgravity environment for 16 days. A longitudinal wall strip of the proximal descending thoracic aorta was subjected to stress-strain and stress-relaxation tests. Wall tensile force was significantly smaller in the spaceflight group than in the two control groups, whereas there were no significant differences in wall stress or incremental elastic modulus at each strain among the three groups. Wall thickness and number of smooth muscle fibers were significantly smaller in the spaceflight group than in the two control groups, but there were no significant differences in amounts of either the elastin or collagen fibers among the three groups. The decreased thickness was mainly caused by the decreased number of smooth muscle cells. Plastic deformation was observed only in the spaceflight group in the stress-strain test. A microgravity environment during spaceflight could affect postnatal development of the morphological and rheological properties of the aorta.

Highlights

It is well known that blood shifts headward immediately after exposure to a microgravity environment and thereafter decreases in volume to adapt to the environment, which could affect cardiovascular hemodynamics and associated regulatory mechanisms [1, 2]
The decrease in fluid volume induced a decrease in cardiac output (CO), which could partly involve lowering of blood pressure [1, 2]
CO has been demonstrated to reduce by approximately 15% from the preflight level in astronauts during sustained spaceflight [5, 6]

Summary

Introduction

It is well known that blood shifts headward immediately after exposure to a microgravity (μG) environment and thereafter decreases in volume to adapt to the environment, which could affect cardiovascular hemodynamics and associated regulatory mechanisms [1, 2]. Central venous pressure (CVP) [3, 4], cardiac output (CO) [5, 6], and arterial pressure (AP) [7, 8] have been reported to instantaneously increase after exposure to μG and decrease in the process of adapting to μG environment during spaceflight in humans. Cardiovascular function changes concomitant with growth after the birth [9]. Blood pressure has been shown to gradually elevate to almost the mature level by the age of 8 weeks [10] or 45 days [11] in Sprague-Dawley (SD) rats and at 4 weeks of age in Wistar Kyoto rats [12]. Baroreceptor sensitivity has been reported to develop with growth [10, 11].

Methods

Results

Conclusion