J. Fareh et al., CARDIAC AND PLASMA ATRIAL-NATRIURETIC-PEPTIDE AFTER 9-DAY HINDLIMB SUSPENSION IN RATS, Journal of applied physiology, 76(2), 1994, pp. 641-649
To determine atrial natriuretic peptide (ANP) adaptation to simulated
weightlessness, immunoreactive plasma (ir-NH2- and ir-COOH-terminals)
and atrial (ir-COOH-terminal) ANP levels, atrial mRNA expression, immu
noreactive cardiocyte ANP levels (ir-NH2- and ir-COOH-terminals), and
ultrastructural observations of granules in atrial cardiocytes were as
sessed in male Wistar rats after a 9-day hindlimb suspension. Plasma i
r-NH2- and ir-COOH-terminal ANP concentrations decreased by 17 (P < 0.
05) and 37% (P < 0.05), respectively, in suspended rats. A concomitant
ir-COOH-terminal ANP content reduction was also observed in left (31%
; P < 0.01) and right atria (25%; P < 0.05). Atrial ANP mRNA expressio
n was severely depleted in the right atrium and less so in the left at
rium after 9 days of hindlimb suspension. Immunocytochemistry observat
ions dem onstrated lowered NH2- and COOH-terminal ANP immunoreactiviti
es in left and right atria from suspended rats. A reduced number of st
orage granules (dense granules) in both atria was also noted on ultras
tructural analysis. It was concluded that ANP biosynthesis, storage, a
nd release were decreased after a 9-day hindlimb suspension.