Neuropeptide Y-induced intestinal absorption: mediation by alpha 2-adrenergic receptors.
In the intestine neuropeptide Y (NPY) is contained in sympathetic nerves, in neuroendocrine cells of the mucosa, and in neurons of the enteric plexuses. After a meal is ingested the concentration of NPY in the blood rises, and intestinal absorption of water and ions increases. We have recently demonstrated a proabsorptive effect of NPY on water and ion transport in the small intestine. The current experiments tested the hypothesis that the alpha 2-adrenergic receptor mediates NPY-induced intestinal absorption. Rabbit ileal segments (n = 35) were harvested and arterially perfused ex vivo. The intestinal lumen was perfused with an isotonic solution containing carbon 14-labeled polyethylene glycol. Net fluxes of H2O, Na+, and Cl- were calculated for three 20-minute periods: basal, drug infusion, and recovery. Five groups were randomly studied: (1) NPY (500 pmol/min); (2) terazosin (1 microgram/min, alpha 1-adrenergic receptor antagonist); (3) NPY + terazosin; (4) yohimbine (1 microgram/min, alpha 2-adrenergic receptor antagonist); and (5) NPY + yohimbine. The infusion of NPY alone caused a significant (p less than 0.05) proabsorptive response for H2O, Na+, and Cl-. Neither terazosin nor yohimbine alone had a significant effect on the transport state of the intestine. Yohimbine, but not terazosin, completely prevented the NPY-induced proabsorptive response. These data support the hypothesis that the proabsorptive effect of NPY is mediated by the alpha 2-adrenergic receptor system.
Department of Surgery, Johns Hopkins Medical Institutions, Baltimore, Md.
G J
GJ
Anthone
M S
MS
Orandle
B H
BH
Wang
C J
CJ
Yeo
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D007082:Ileum / Q000187:drug effects; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D009478:Neuropeptide Y / Q000502:physiology*; D011224:Prazosin / Q000031:analogs & derivatives / Q000494:pharmacology; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D009478:Neuropeptide Y; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; C041226:Terazosin; D011224:Prazosin