Pyridoxal-5'-phosphate: A cost-effective treatment candidate for hypertensive patients?

OBJECTIVES: Because angiotensin (Ang) II is an essential vasoconstrictive peptide, we analyzed the impact of its post-translational modification to pyruvamide-Ang II (Ang P) by pyridoxal-5'-phosphate (PLP) on blood pressure. PLP is a less expensive vitamin B derivative and, therefore, could be a cost-effective drug against hypertension. METHODS: Effect of Ang P on calcium ion entry into vascular smooth muscle cells (VSMCs) was analyzed. Binding affinity of Ang P to angiotensin II type 1 receptor (AT R) was measured. Vasoconstrictive effect of Ang P was investigated using the bioassay of isolated perfused rat kidneys. Spontaneously hypertensive rats (SHR) were administered PLP. Additionally, Wistar Kyoto rats (WKY) received Ang II and PLP. Blood pressure was measured time-dependently. RESULTS: Ang II, incubated with PLP, was post-translationally modified to Ang P. Calcium ion entry in VSMCs was significantly lower with Ang P compared to Ang II. Binding affinity of Ang P to AT R was lower compared to Ang II. Perfusion pressure of isolated perfused rat kidneys increased less by Ang P than by Ang II. Blood pressure of SHR treated with PLP decreased significantly. Blood pressure of WKY rats treated with Ang II was increased to hypertensive values, whereas blood pressure of WKY rats cotreated with Ang II and PLP was not. CONCLUSION: PLP induces a post-translational modification of Ang II decreasing blood pressure in rats. Assuming that increased PLP intake in the form of vitamin B might reduce blood pressure in hypertensive patients, PLP might be a cost-effective drug against hypertension.