On the Antihypertensive Properties of Nitrendipine, with Observations of Its Effects on Electrolyte Excretion

Summary

The weekly implantation of 25 mg nitrendipine pellets effectively prevented spontaneous and DOC-salt hypertension and were well tolerated. In the latter model steroid-induced “diabetes insipidus-like” syndrome was also prevented.

Nitrendipine acted differently in rats with spontaneous hypothalamic diabetes insipidus than it did in normal Long-Evans rats. When 0.7% NaCl was used as the loading solution, the latter responded with polyuria, lowered urine osmolality, natriuresis and kaliuresis, none of which occurred in DI rats. When the loading solution consisted of 0.45% NaCl + 0.25% KCl, nitrendipine caused polyuria in normal rats, without any effect on electrolyte excretion, and decreased electrolyte excretion without affecting urine volume in DI rats.

When loading solutions of 0.9% NaCl, 0.9% KCl and 5.1% glucose were used, the response to nitrendipine was again different. In the first instance the drug caused polyuria, hypernatremia and hyperkalemia without affecting urine osmolality: in the second it had no effect, and in the third it caused hyponatremia. When dual solute solutions of NaCl + glucose, NaCl + KCl, or KCl + glucose were used, there were still different responses. With the first, nitrendipine reduced urinary Na⁺ and K⁺, with the second it also reduced urine volume, and with the third it increased urine output while diminishing urine osmolality and K⁺ excretion.