Effects of atriopeptin and chicken heart extract in Gallus domesticus

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Abstract
Effects of Ser-Leu-Arg-Arg-atriopeptin III (ANP) and chicken heart extract (CHE) were compared during unilateral renal portal infusion in anesthetized Single Comb White Leghorn chickens. The purpose was to determine whether renal effects were glomerular and/or tubular. Both CHE and ANP caused substantial decreases in mean arterial pressure but had different renal actions. ANP caused small but significant increases in both absolute and fractional sodium excretion, but these effects were modest compared with those reported in mammals. Although there was a tendency for higher fractional sodium excretion in the portal infused kidney, the difference was not significant (0.1 less than P greater than 0.05). ANP also increased glomerular filtration rate (GFR), urine flow rate (UFR), and osmolal clearance and decreased estimated renal vascular resistance. In contrast, CHE decreased GFR and increased resistance. In contrast, CHE decreased GFR and increased fractional potassium excretion in the infused kidney. After CHE infusion was stopped, GFR and UFR increased, and there was a further transient kaliuresis. No natriuretic effects were ever seen with CHE. Chickens apparently lack potent mammalian-type cardiac natriuretic factor(s) and/or have a limited capacity for natriuresis in response to mammalian ANP. Because hypotension was the most prominent avian response to both CHE and ANP, endogenous vasoactive factor(s) in chicken hearts may function to regulate blood pressure rather than blood volume.