PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE - OCCURRENCE AND RELAXANT EFFECT IN FEMALE GENITAL-TRACT

The distribution, localization, and smooth muscle effects of pituitary adenylate cyclase-activating polypeptide (PACAP) were studied in the human female genital tract. The concentrations of PACAP-38 and PACAP-2 7 were measured by radioimmunoassays, and both peptides were found thr oughout the genital tract. The highest concentrations of PACAP-38 were detected in the ovary, the upper part of vagina, and the perineum. Th e concentrations of PACAP-27 were generally low, in some regions below the detection Limit and in other regions 1 to 5% of the PACAP-38 conc entrations. Immunocytochemistry revealed that PACAP was located in del icate varicose nerve fibers that were most abundant in the internal ce rvical os, where they mainly seemed to innervate blood vessels and smo oth muscle cells. PACAP-38 and PACAP-27 (10(-10)-10(-6) M) caused a co ncentration-dependent relaxation of the spontaneous activity of the no nvascular smooth muscle strips from fallopian tube and myometrium in v itro. Likewise, both peptides (10(-10)-10(-6) M) caused relaxation of norepinephrine (10(-6) M)-precontracted intramyometrial arteries. No e ffect of the PACAP sequences, PACAP-(6-27), PACAP-(16-38), and PACAP-( 18-27), on fallopian tube was observed. The findings suggest a smooth muscle regulatory role of PACAP in the human female reproductive tract .