HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 105/2/569    most recent 01381.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Yin, W. Articles by Pei, J.-M. PubMed PubMed Citation Articles by Yin, W. Articles by Pei, J.-M.

Modulation of β-adrenoceptor signaling in the hearts of 4-wk simulated weightlessness rats

¹Department of Emergency, Xijing Hospital; ²Department of Physiology, National Key Discipline of Cell Biology; ³School of Aerospace Medicine, and ⁴Department of Cardiac Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi Province, People's Republic of China

Submitted 31 December 2007 ; accepted in final form 9 May 2008

The modulation of β-adrenoceptor signaling in the hearts of hindlimb unweighting (HU) simulated weightlessness rats has not been reported. In the present study, we adopted the rat tail suspension for 4 wk to simulate weightlessness; then the effects of simulated microgravity on β-adrenoceptor signaling were studied. Mean arterial blood pressure (ABP), left ventricular pressure (LVP), systolic function (+dP/dt_max), and diastolic function (–dP/dt_max) were monitored in the course of the in vivo experiment. Single rat ventricular myocyte was obtained by the enzymatic dissociation method. Hemodynamics, myocyte contraction, and cAMP production in response to β-adrenoceptor stimulation with isoproterenol or adenylyl cyclase stimulation with forskolin were measured, and Gs protein was also determined. Compared with the control group, no significant changes were found in heart weight, body weight and ABP, while LVP and ±dP/dt_max were significantly reduced. The ABP decrease, LVP increase, and ±dP/dt_max in response to isoproterenol administration were significantly attenuated in the HU group. The effects of isoproterenol on electrically induced single-cell contraction and cAMP production in myocytes of ventricles in the HU rats were significantly attenuated. The biologically active isoform, Gs (45 kDa) in the heart, was unchanged. Both the increased electrically induced contraction and cAMP production in response to forskolin were also significantly attenuated in the simulated weightlessness rats. Above results indicated that impaired function of adenylyl cyclase causes β-adrenoceptor desensitization, which may be partly responsible for the depression of cardiac function.

simulated weightlessness; β-adrenoceptor; adenylyl cyclase; cyclic adenosine 5'-monophosphate