AJP - Endocrinology and Metabolism, Vol 251, Issue 1 48-E51, Copyright © 1986 by American Physiological Society
Peptides PHI and VIP: comparison between vascular and nonvascular smooth muscle effect in rabbit uterus
B. Bardrum, B. Ottesen and J. Fahrenkrug
The distribution and effects of the two neuropeptides, vasoactive
intestinal polypeptide (VIP) and peptide histidine isoleucine amide (PHI),
on vascular and nonvascular smooth muscle in the urogenital tract of
nonpregnant rabbit female, were investigated. Immunoreactive VIP and PHI
were present in all regions except the ovary with the highest concentration
in the uterine cervix. By using in vitro tension recordings of myometrial
specimens, it was demonstrated that both peptides displayed a
dose-dependent inhibition of the mechanical activity. The dose-response
curves of VIP and PHI were superimposable with and ID50 of 3 X 10(-8)
mol/l, and their combined effect was additive. In addition, the influence
of the two peptides on myometrial blood flow (MBF) was investigated by the
xenon-133 washout technique. Both peptides were found to increase MBF with
the same potency and efficacy. Their combined effect was additive. In
conclusion VIP and PHI are present in the rabbit urogenital tract, and the
two peptides are equipotent inhibitors of mechanical nonvascular and
vascular smooth muscle activity in the uterus.
