A Potent Hypotensive Factor in Chicken Left Ventricle (4261 5)

Chicken artria and ventricles both have membrane-bound granules which resemble those containing atriopeptin.(ANP) in mammals. However, nothing is known about the con- tents of the avian granules. A previous study in chickens showed that although extracts of whole chicken heart or synthetic rat ANP both caused profound hypotension, ANP caused both natriuresis and diuresis, while chicken heart extract did not. The present study sought to locate the region(s) of chicken heart containing the hypotensive activity, and to observe the effect on sodium and water excretion and blood pressure in rats. Acid extracts of either atrium, either ventricle, ventricular septum, skeletal muscle, and liver were identically prepared from chickens and rats. Extracts were adjusted to the same protein concentration and injected (0.15 ml/kg) into anesthetized Single Comb White Leghorn roosters. Mean arterial pressure (MAP) and the time for recovery were measured. The most potent extract from chicken hearts was from the left ventricle (-38 +- 1 mm Hg, 149 ? 9 sec to recover). All other extracts (including right ventricle) produced only small (10-20 mm Hg), short-lived (20-30 sec) decreases in MAP. In contrast, only rat atrial extracts evoked long-lasting hypotension (>40 mm Hg, recovery time >200 sec). A 30-min infusion of the most potent chicken extract (left ventricle, CLV) into rats produced a small but significant natriuresis and diuresis compared to the vehicle time control (P < 0.05) and the hypotensive response to bolus injection was about one-third that seen in the chicken. The location of potent spasmolytic activity primarily in chicken left ventricle, the different avian renal responses to chicken heart extract and synthetic rat ANP (5), and the weak diuretic, natriuretic, and hypotensive effects of CLV extract in rats all suggest that the chicken heart substance may be different from mammalian ANP. 0 1987 Society for Experimental Biology and Medicine.