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Biology of Reproduction 65, 1224-1231 (2001)
© 2001 Society for the Study of Reproduction, Inc.

Regular Article

Fertilization of Sea Urchin Eggs and Sperm Motility Are Negatively Impacted under Low Hypergravitational Forces Significant to Space Flight1

Joseph S. Tash2,a, Shane Kima, Marianne Schuberc, Dieter Seibtc, and William H. Kinseyb

a Department of Molecular & Integrative Physiology, b Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas 66160 c Microgravity User Support Center, German Aerospace Center (DLR), 51147 Köln, Germany

ABSTRACT

Sperm and other flagellates swim faster in microgravity (µG) than in 1 G, raising the question of whether fertilization is altered under conditions of space travel. Such alterations have implications for reproduction of plant and animal food and for long-term space habitation by man. We previously demonstrated that µG accelerates protein phosphorylation during initiation of sperm motility but delays the sperm response to the egg chemotactic factor, speract. Thus sperm are sensitive to changes in gravitational force. New experiments using the NiZeMi centrifugal microscope examined whether low hypergravity (hyperG) causes effects opposite to µG on sperm motility, signal transduction, and fertilization. Sperm % motility and straight-line velocity were significantly inhibited by as little as 1.3 G. The phosphorylation states of FP130, an axonemal phosphoprotein, and FP160, a cAMP-dependent salt-extractable flagellar protein, both coupled to motility activation, showed a more rapid decline in hyperG. Most critically, hyperG caused a ~50% reduction in both the rate of sperm-egg binding and fertilization. The similar extent of inhibition of both fertilization parameters in hyperG suggests that the primary effect is on sperm rather than eggs. These results not only support our earlier µG data demonstrating that sperm are sensitive to small changes in gravitational forces but more importantly now show that this sensitivity affects the ability of sperm to fertilize eggs. Thus, more detailed studies on the impact of space flight on development should include studies of sperm function and fertilization.

FOOTNOTES

First decision: 23 April 2001.

1 This research was supported by funds from the National Aeronautics and Space Administration (NASA, NAG 2-1016) and by NICHD/National Institutes of Health through cooperative agreement U54 HD-33994 as part of the Specialized Cooperative Centers Program in Reproductive Research.

2 Correspondence: Joseph S. Tash, Dept. Molecular & Integrative Physiology, University of Kansas Medical Center, Lied G-005, 3901 Rainbow Blvd., Kansas City, KS 66160-7401. FAX: 913 588 7180; jtash{at}kumc.edu






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Copyright © 2001 by the Society for the Study of Reproduction.