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Relaxant effect of rat PHI, PHI-Gly and PHV(1-42) in the rat gastric fundus
R A Lefebvre1, S Sas, A Cauvin
1Heymans Institute of Pharmacology, Medical School, University of Gent, Belgium.
Abstract:
It was previously shown that porcine PHI is 30 times less potent than VIP in relaxing the rat gastric fundus; the relaxant potency of rat PHI and its 2 C-terminally extended forms PHI-Gly and PHV(1-42) in the rat gastric fundus was compared here with that of VIP, porcine PHI and PHM. The rank order of potency in relaxing the precontracted fundus tissues was VIP greater than rat PHI greater than PHM greater than PHV greater than PHI-Gly greater than porcine PHI, rat PHI being only 2 times less potent than VIP. In the presence of antioxidants, the potency and efficacy of porcine PHI increased, but the peptide was still the least potent of the series tested. The results illustrate the importance of using species-related peptides and are compatible with a cotransmitter role of rat PHI in nonadrenergic noncholinergic neurotransmission of the rat gastric fundus.