Cyclic fluctuations of vasoactive intestinal polypeptide measured radioimmunologically in various regions of the human fallopian tube.

: Levels of the neuropeptide VIP were measured by radioimmunoassay in the isthmus, ampulla, and fimbriated end of the human fallopian tube during the follicular, ovulatory, and luteal phases as defined by plasma estradiol and progesterone concentrations. The regional concentration of VIP was in the order isthmus greater than ampulla greater than fimbriae. The VIP concentration increased by 170% from the follicular through the ovulatory to the luteal phase in the isthmus. Such a tendency was seen also in the ampulla when the peptide level was expressed in terms of the total regional content. In fact, when expressed as total content, VIP was highest in the ampulla at all cyclic stages. Since there are no major fluctuations in the water content of the tubal tissues in the three phases, the observed changes in VIP levels represent real fluctuations at the neural level in a manner similar to that previously shown for the neurotransmitter norepinephrine.