Effects of parathyroid hormonal peptides on the gut

Our previous studies have shown PTH to be an effective relaxant of smooth muscle throughout the mammalian tract. Recently, we found PTHrP to be equally as potent and effective on the gut as PTH, and we hypothesized that PTHrP, rather than PTH, might be the natural ligand for the gut receptors which mediate GI smooth muscle relaxation. To approach this question, we asked whether rat GI tissue expresses mRNA for PTHrP. Using selective reverse transcription and PCR we have found PTHrP mRNA in smooth muscle throughout the rat GI tract and in gastric and colonic mucosa as well. Our findings support the idea that PTHrP can be produced by GI tissues and that it may function there as an autocrine or paracrine factor. One of its actions may involve regulation of GI muscle tone.