Effects of Atrial Appendectomy on Circulating Atrial Natriuretic Factor during Volume Expansion in the Rat

Abstract

This study examined the changes in the circulating level of endogenous atrial natriuretic factor during diuresis and natriuresis produced by acute volume expansion in anesthetized rats with either bilateral atrial appendectomy ( n = 9) or sham operation ( n = 9). Following control measurements in the sham-operated rats, 1 % body weight volume expansion with isotonic saline produced an increment in urinary sodium excretion of over 4 peqlmin ( P < 0.05) while urine volume increased by more than 20 pl/min ( P < 0.05). These responses were associated with a significant increase in immunoreactive plasma atrial natriuretic factor from a baseline value of 82 2 10 pg/ml to a level of 120 f 14 pg/ml (P < 0.05). In contrast, in the group of rats with bilateral atrial appendectomy an identical degree of volume expansion increased urinary sodium excretion and urine volume by only 0.61 peq/min (P < 0.05) and 3.07 pl/min (P < 0.05), respectively. In this group, immunoreactive plasma atrial natriuretic factor remained statistically unchanged from a control value of 70 k 12 pg/ml to a level of 82 k 16 pg/ml (P > 0.05).Comparison of the two groups indicates that the natriuresis, diuresis, and plasma atrial natriuretic factor levels during volume expansion were significantly reduced in the rats with bilateral atrial appendectomy. No differences in mean arterial pressure and heart rate were observed between the two groups. These data demonstrate that removal of both atrial appendages in the rat attenuated the release of atrial natriuretic factor during volume expansion; and this effect, in turn, was associated with a reduction in the natriuretic and diuretic responses. o 1986 Society for Experimental Biology and Medicine.

Effect of Changes in Sodium Intake on Atrial Natriuretic Factor (ANF) and Peptides Derived from the N Terminus of the ANF Prohormone in the Rat

“…Atrial appendectomy in the rat has been shown to attenuate both the rise in ANF (4) and the natriuresis (3,4) in response to acute volume expansion. This response can also be attenuated by prior administration of monoclonal antibodies directed against ANF (5).…”

The Role of the Left Atrial Appendage. A Volume Loading Study in Open-chest Dogs.

“…These facts may explain the inconsistency between appendage dimensional changes in the present study and the flow pattern described by Suetsugu et al12) Some previous studies have shown that left atrial appendectomy caused few hemodynamic changes. 13,14) The left appendage may not be important in hearts with an intact left ventricle. In this study, however, the appendage clearly acted as a booster pump showing greater fractional shortening than the atrial body , and moreover, the appendage had a Frank Starling mechanism during volume loading similar to that of the atrial body .…”

An update on the physiology of atrial natriuretic factor.

“…Removal of the atrial appendages, which are major storage sites for proANF, blunted the volume-induced increase in plasma ANP and reduced the ability of anesthetized 9 ' 10 and conscious" rats to excrete an acute intravenous volume load. This suggested that less ANF was available for release in the rats that had undergone atrial appendectomy, and that an attenuated increment in plasma ANF level accounted for the blunted natriuretic and diuretic responses.…”