Objectives:Atriopeptins are of interest in space flight due to their putative involvement in the adjustment of astronauts to the cephalad shift of body fluid experienced in orbital flight. This shift of some two liters of fluid is thought to stimulate right atrial stretch receptors, resulting in the release of atriopeptins which cause natriuresis and diuresis by direct action on the kidney, inhibition of aldosterone and vasopressin secretion, and by dilation of large vessels which further enhances central pooling of blood. In this study, atriopeptin (AP-3) was examined in the atria and plasma of space-flown rats.
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Approach:
Right and left atria were dissected separately and about 40 mg of tissue from the ventricular apex was removed. A plasma sample was also taken. After transport, samples were analyzed for atriopeptin immunoreactivity (APir) by radioimmuno- assay. To determine if the halothane anesthesia or decapitation might have altered APir, a group of sixteen rats equipped with chronic catheters in their left carotid artery were also studied. Half of the rats were anesthetized with halothane, and a blood sample was taken from the catheter of all rats before sacrifice. Laboratory catheter and trunk samples were then similarly analyzed for APir.
Results:
While the flight animals' right and left atria had higher levels of AP-3 than the synchronous controls, the difference was not statistically significant. Due to the high level of uncontrolled stresses on both groups of rats, the observed values cannot be considered representative of basal AP-3 levels in the rat. The laboratory study demonstrated the profound effect of the halothane anesthesia on AP-3. Plasma AP-3 levels of rats anesthetized were over 400% higher than in conscious controls. It is evident that the large number of stresses connected with transporting and handling animals for space flight make it essential that studies of labile factors such as atriopeptins be conducted on samples obtained inflight, rather than attempting to rely solely on postflight sampling.
Inge WH, Hartle DK. Atriopeptin (AP-3) in Atria and Plasma of Rats Orbited Aboard NASA Spacelab (SL3) for seven days. Abstract S-231; Proceedings of the Seventh Annual Meeting on the IUPS Commission on Gravitational Physiology; 1985 Oct 13-18; Niagara Falls (NY); 1985:S231
Inge WH, Hartle DK. Atriopeptin (AP-3) in atria and plasma of rats orbited aboard NASA Spacelab (SL3) for seven days; Abstract 83.27; 36th Annual Fall Meeting of the American Physiological Society; 1985 Oct 13-18; Buffalo (NY) Physiologist 1985; 28(4):380.
Inge WH, Hartle DK. Atriopeptin (AP-3) in Atria and Plasma of Rats Orbited Aboard NASA Spacelab (SL3) for seven days; Physiologist 1985; 28(6 Suppl):S231-2.
Content, Atriopeptin (AP-3), atria, ventricular apex, heart, rat, radioimmuno- assay,
Content, Atriopeptin (AP-3), plasma, rat, radioimmuno- assay