Variable acceleration influences cyclic AMP levels in Paramecium biaurelia

• Published in: Journal of gravitational physiology Vol. 9; no. 1; p. P267
• Main Authors: Hemmersbach, Ruth, Wilczek, Manuela, Stieber, Christiane, Braucker, Richard, Ivanova, Krassimira
• Format: Journal Article
• Language: English
• Published: United States 01.07.2002
• ISSN: 1077-9248

Paramecium is used as a model system to analyse the gravity signal transduction pathway, that leads to gravitaxis and gravikinesis. In order to prove whether gravistimulation is coupled with second messenger production (cyclic AMP: hyperpolarization, cyclic GMP: depolarization) Paramecium was fixated under variable accelerations (1 x g, 9 x g and 10(-4) x g) on a centrifuge and during a sounding rocket flight (TEXUS 39). The analysis of cAMP and cGMP levels revealed an acceleration-dependent change in cAMP, while cGMP-levels showed gravity-independent variations. Hypergravity did not only induce an amplification of gravitaxis and gravikinesis, but also an increase in cAMP compared to the 1 x g-data. We conclude that the increased pressure of the cytoplasm on the lower membrane of upward swimming cells enhance the number of open K+(-)channels, thus causing hyperpolarization and change in cAMP concentration. Consequently, transition to microgravity declines gravitaxis and gravikinesis, and decreases cAMP concentration due to the loss of pressure on the cell membrane.