INCREASED EXPRESSION OF PARATHYROID HORMONE-RELATED PEPTIDE GENE IN BLOOD-VESSELS OF SPONTANEOUSLY HYPERTENSIVE RATS

We have shown recently that mechanical stretch of cultured rat aortic smooth muscle cells induces a marked increase in gene expression of th e vasorelaxant parathyroid hormone-related peptide. In the present stu dy, we investigated whether mechanical force affected the in vivo para thyroid hormone-related peptide gene expression in blood vessels, Nort hern blot analysis revealed that stretch of isolated rat aortic strips increased the expression level of parathyroid hormone-related peptide mRNA. The parathyroid hormone-related peptide transcript level in aor ta and mesenteric vessels from 18-week-old spontaneously hypertensive rats (SHR) was 2.5- and 2.2-fold higher, respectively, compared with a ge-matched Wistar-Kyoto (WKY) controls, whereas the parathyroid hormon e-related peptide mRNA level in aorta from normotensive 4-week-old SHR was similar to that of age-matched WKY controls, The aortic parathyro id hormone-related peptide content was higher in 18-week-old SHR than in age-matched WKY controls. Moreover, treatment of mature SHR with an angiotensin II type 1 receptor antagonist or hydralazine caused a con comitant decrease in the parathyroid hormone-related peptide transcrip t level in aorta with lowering of blood pressure. These results sugges t that the in vivo parathyroid hormone-related peptide gene expression in blood vessels is under the control of mechanical force, pointing t o a role of parathyroid hormone-related peptide in the regulation of v ascular tone.