Effects of natriuretic peptides on the gill vasculature of a hagfish, Eptatretus cirrhatus

An isolated, perfused gill pouch preparation and myography were used to det ermine responses of the branchial vasculature of a hagfish to the mammalian natriuretic peptides, rANP and CNP. In the isolated gill pouch preparation afferent perfusion pressures increased in the first 5 min of exposure to l ow concentrations (10(-14) to 10(-10)M) of ANP and CNP and then decreased b elow starting values by 15 min. At higher concentrations the depressor resp onse prevailed and natriuretic peptides switched the flow away from the eff erent artery to the venous route, which would fill the peribranchial sinus in vivo. At low concentrations ANP increased circumferential tensions in af ferent branchial arterial rings. At higher concentrations afferent and effe rent branchial arteries relaxed in response to ANP and CNP.