Can serum albumin level affect the pharmacological action of tolvaptan in patients with liver cirrhosis? A post hoc analysis of previous clinical trials in Japan.

BACKGROUND: Patients with hypoalbuminemia often fail to respond to increased doses of loop diuretics. We therefore performed a post hoc analysis to investigate the pharmacological action of tolvaptan and whether it is dependent on the serum albumin level. METHODS: This analysis was based on four previous clinical trials of tolvaptan in patients with liver cirrhosis who exhibited insufficient response to conventional diuretics. We analyzed the correlation between the change in the initial 24-h cumulative urine volume from baseline and the serum albumin level at baseline, and assessed potential predictive factors of response to tolvaptan. RESULTS: The correlation coefficient was 0.029 in the placebo group and -0.112 in the 7.5 mg tolvaptan group of patients with liver cirrhosis. Administration of tolvaptan provoked a stable response regardless of the serum albumin level. Tolvaptan use was identified as a significant predictor of pharmacological action, and was shown to change the initial urine volume by 885 mL (P < 0.0001) in liver cirrhosis patients. CONCLUSIONS: In this post hoc analysis, tolvaptan increased the initial urine volume from baseline regardless of serum albumin levels. Use of tolvaptan as an add-on therapy to loop diuretics can be considered an optimal therapeutic option in patients with insufficient response to loop diuretics.

Antiproliferative action of an angiotensin I-converting enzyme inhibitory peptide, Val-Tyr, via an L-type Ca2+ channel inhibition in cultured vascular smooth muscle cells.

Recent antihypertensive studies have demonstrated that small peptides with angiotensin I-converting enzyme (ACE) inhibitory activity had an ability to lower or to modulate a pressor blood pressure response in mild hypertensive subjects. However, the underlying mechanisms still remain unclear. Based on our previous finding that a small peptide, Val-Tyr (VY), was accumulated in the rat aorta and kidney as well as in the circulating blood system, we here investigated whether antihypertensive small peptides exert an antiproliferative effect on serum- or mitogen-induced human vascular smooth muscle cells (VSMCs). Treatment with some ACE inhibitory small peptides (VY, Ile-Trp [IW], and Ile-Val-Tyr [IVY]) had diverse effects on serum-stimulated VSMC proliferation that were independent of their ACE inhibitory activity, though only VY exerted a potent antiproliferative action. VY also showed a greater inhibition of WST-8 incorporation in response to angiotensin (Ang) II-stimulation than the other two small peptides. The attenuation of Ang II-stimulated WST-8 incorporation by VY was not affected by Ang II receptor antagonists (losartan and saralasin ([Sar1, Ile8]-Ang II)), indicating that the antiproliferative action of VY may not be due to the peptide's antagonistic effect against Ang II receptors. Treatment with VY had a significant inhibitory effect on the WST-8 incorporation induced by the stimulation of a voltage-gated L-type Ca2+ channel agonist, Bay K 8644. Even in the presence of a K+ channel blocker (paxillin) the inhibition was apparent, suggesting that VY inhibited the proliferation of VSMCs by serving as a natural L-type Ca2+ channel blocker, but not as a K+ channel agonist.

Tissue distribution of antihypertensive dipeptide, Val-Tyr, after its single oral administration to spontaneously hypertensive rats.

The distribution of an antihypertensive dipeptide, Val-Tyr (VY), in the tissues of spontaneously hypertensive rats (SHR) was investigated in this study. A single oral administration of VY (10 mg/kg) to 18-week-old SHR resulted in a prolonged reduction of systolic blood pressure (SBP) up to 9 h (SBP0h 198.0+/-3.6 mmHg; SBP9h 154.6+/-3.5 mmHg). As a result of VY determination, a roughly 10-fold higher increment of plasma VY level was observed at 1 h than that at 0 h, whereas thereafter the level declined rapidly. In tissues, VY was widely accumulated in the kidney, lung, heart, mesenteric artery and abdominal aorta with the area under the curve over 9 h of more than 40 pmol h/g tissue; of these a higher VY level was observed in the kidney and lung. In addition, a mean resident time (MRT) for each tissue (>5 h except for liver) revealed that VY preferably accumulated in the tissues rather than in the plasma (MRT 3.8 h). Significant reductions of tissue angiotensin I-converting enzyme activity and angiotensin II level were found in the abdominal aorta as well as in the kidney, suggesting that these organs could be a target site associated with the antihypertensive action of VY.