AJP - Endocrinology and Metabolism, Vol 262, Issue 1 E52-E57, Copyright © 1992 by American Physiological Society
Circulating galanin: origin, metabolism, and pharmacokinetics in anesthetized pigs
H. Harling and J. J. Holst
Department of Surgical Gastroenterology C, Rigshospitalet, Copenhagen, Denmark.
The concentration of galanin-like immunoreactivity (GAL-LI) was 12.9 +/-
0.9 pmol/l in porcine arterial plasma (n = 9) and ranged from 1 to 14
pmol/g in extracts of porcine gastrointestinal tract (n = 5), the colon
being the richest gut segment. A significant (P less than 0.05)
arteriovenous concentration difference of circulating endogenous GAL-LI
occurred across the kidney (15.1 +/- 2.3 vs. 6.2 +/- 0.5 pmol/l) and a hind
leg (15.7 +/- 2.5 vs. 10.2 +/- 1.0 pmol/l), whereas a negative gradient was
observed across the intestine (12.5 +/- 2.0 vs. 17.7 +/- 3.3 pmol/l) of
anesthetized pigs. Passage through the brain, liver, or lungs did not
change the concentration of endogenous GAL-LI significantly. During basal
circumstances, the major source of circulating GAL-LI is therefore the gut.
During infusion of 20 pmol.kg-1.min-1 of synthetic porcine galanin, a
significant extraction occurred across the kidney (64.8 +/- 4.3%), hind leg
(20.3 +/- 3.8%), and liver (19.7 +/- 4.3%). The overall metabolic clearance
rate was 37.8 +/- 3.7 ml.min-1.kg-1. The half-life of galanin in plasma was
4.6 +/- 0.3 min, and the apparent distribution space was 255.6 +/- 31.4
ml/kg. Incubation studies in vitro showed that the concentration of
galanin, added to blood and plasma at 37 degrees C, was halved in 1 h,
unless stabilized with EDTA and aprotinin.
