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The effects in the rat of two fragments of parathyroid hormone‐related protein on uterine contractions in situ
Author(s) -
Barri ME,
Abbas SK,
Care AD
Publication year - 1992
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.1992.sp003608
Subject(s) - acetylcholine , endocrinology , medicine , parathyroid hormone , chemistry , acetylcholine receptor , receptor , calcium , biology , biochemistry
Synthetic parathyroid hormone fragment PTH(1–34) has been reported recently to inhibit uterine contractions stimulated by a variety of agonists. We have studied the effect in this system of the parathyroid hormone‐related protein fragment PTHrP(1–34) which shows 60% homology with PTH over the first thirteen amino acid residues. The effects of two different PTHrP fragments on acetylcholine‐stimulated uterine contractions in vitro were studied. Whereas synthetic hPTHrP(75–86 amide) (10(−9)−10(−7) M) was without effect, synthetic hPTHrP(1–34) (10(−9)−10(−7) M) was capable of inhibiting, in a dose‐related fashion, uterine muscle contractions precontracted with 10(−6) M‐acetylcholine. In a second series of experiments the bovine PTH(3–34) fragment itself was shown to have no stimulatory effect on acetylcholine‐stimulated contractions. Also this fragment in an equimolar concentration (10(−7) M) failed to antagonize the effects of PTHrP(1–34) on acetylcholine‐stimulated uterine contractions. However, a 100‐fold excess molar concentration of bPTH(3–34) (10(−6) M) completely abolished the inhibitory action of hPTHrP(1–34) (10(−8) M) on acetylcholine‐stimulated uterine contractions. These results clearly show that the inhibitory action of PTH(1–34) and PTHrP(1–34) on uterine contractions depends on the integrity of the amino‐terminal region of the molecule.