AJP - Heart and Circulatory Physiology, Vol 251, Issue 5 1095-H1099, Copyright © 1986 by American Physiological Society
Effect of atrial contraction frequency on atrial natriuretic peptide secretion
R. J. Schiebinger and J. Linden
Paroxysms of atrial tachycardia are oftentimes associated with polyuria.
The plasma levels of the potent diuretic hormone, atrial natriuretic
peptide (ANP), are elevated during episodes of atrial tachycardia,
suggesting that ANP may play a role in mediating the diuresis. The
mechanism of enhanced ANP secretion associated with atrial tachycardia is
not known. We examined the effect of altering the pacing frequency of
isolated left rat atria on ANP secretion. Atria were suspended between an
electrode and hook connected to a force transducer and superfused with
medium 199. The ANP content of the superfusate was measured by
radioimmunoassay. Increasing the frequency of pacing from 2 to 4 Hz
resulted in a 46 +/- 5% (means +/- SE, n = 9) rise in immunoreactive ANP
secretion above base line (P less than 0.01). Lowering the frequency from 4
to 2 Hz lowered immunoreactive ANP secretion by 36 +/- 3% (n = 6) relative
to base line (P less than 0.02). Incremental increases in the pacing
frequency from 2 to 8 Hz resulted in a continual rise in immunoreactive ANP
with a peak increase of 191 +/- 6% of base line (n = 8) at 8 Hz. To examine
the possibility that release of norepinephrine or acetylcholine from
endogenous nerves mediated this effect, the atria were superfused with the
combination of 0.1 microM propranolol, 1.0 microM phentolamine, and 10
microM atropine. The concentrations of the antagonists were 125-fold or
higher than the dissociation constant for binding to receptors.(ABSTRACT
TRUNCATED AT 250 WORDS)
