Canine liver releases neuropeptide Y during sympathetic nerve stimulation.
To determine whether the liver or gut releases neuropeptide Y (NPY) from their sympathetic nerves, we performed bilateral thoracic sympathetic nerve stimulation (BTSNS) in halothane-anesthetized dogs and calculated gut and liver NPY spillover. BTSNS markedly increased hepatic NPY spillover (delta = +32 +/- 8 ng/min) and arterial NPY concentration (delta = +220 +/- 56 pg/ml), despite no effect on gut NPY spillover (delta = +8 +/- 7 ng/min). To determine the liver's contribution to this increase of circulating NPY, hepatic nerves were selectively stimulated (HNS). Liver NPY spillover increased markedly (delta = +114 +/- 42 ng/min, P < 0.025) during HNS, causing a large increase of arterial NPY (delta = +586 +/- 237 pg/ml, P < 0.025). Using this ratio of liver spillover to arterial increments of NPY, we calculated that the liver makes a major contribution (70%) to circulating NPY levels during BTSNS. The predominant form of canine NPY coeluted with synthetic [Met17]NPY and the minor form of canine NPY coeluted with the oxidized form of [Met17]NPY on high-performance liquid chromatography. We therefore conclude that dog NPY is likely [Met17]NPY and that the liver, rather than the gut, is a major source of circulating NPY during sympathetic nerve stimulation and perhaps stress.
Taborsky
G J
GJ
Department of Medicine, Veterans Affairs Medical Center, University of Washington, Seattle 98108.
Beltramini
L M
LM
Brown
M
M
Veith
R C
RC
Kowalyk
S
S
D000818:Animals; D004285:Dogs; D004558:Electric Stimulation; D005947:Glucose / Q000378:metabolism; D006400:Hematocrit; D006499:Hepatic Artery; D006503:Hepatic Veins; D007700:Kinetics; D008099:Liver / Q000294:innervation* / Q000378:metabolism*; D008102:Liver Circulation; D009478:Neuropeptide Y / Q000097:blood / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D011169:Portal Vein; D013564:Sympathetic Nervous System / Q000502:physiology*; D013909:Thorax; D013997:Time Factors
D009478:Neuropeptide Y; D005947:Glucose; D009638:Norepinephrine