Diminished mesenteric vaso- and venoconstriction and elevated plasma ANP and BNP with simulated microgravity

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Vascular Biology

Background:

• Microgravity and bed rest impair vascular constriction, affecting orthostatic tolerance.
• Small mesenteric vessels may be uniquely affected due to different pressure dynamics.

Purpose of the Study:

• To investigate the impact of simulated microgravity (head-down tail suspension) on adrenergic responsiveness in rat mesenteric arteries and veins.
• To determine if elevated natriuretic peptides contribute to vascular dysfunction.

Main Methods:

• In vitro study of mesenteric arteries and veins from control and head-down tail suspension rats.
• Assessment of norepinephrine-induced vasoconstriction and venoconstriction.
• Measurement of plasma atrial natriuretic peptide (ANP) and NT-proBNP levels.

Main Results:

• Head-down tail suspension reduced arterial sensitivity and maximal responsiveness to norepinephrine.
• Mesenteric veins showed diminished venoconstriction to norepinephrine after head-down tail suspension.
• Plasma ANP and NT-proBNP levels were elevated in head-down tail suspension rats.
• Elevated ANP/BNP diminished maximal arterial and venous constrictor responses.

Conclusions:

• Simulated microgravity impairs adrenergic responsiveness in small mesenteric arteries and veins.
• Elevated natriuretic peptides may play a role in this reduced vascular constrictor function.
• Findings suggest potential mechanisms for altered vascular control during spaceflight.