The Effet of Nifedipine on the Blood Pressure, Water and Cation Balance of the Lens in Spontaneous Hypertensive Rats

ABSTRACT

In systemic hypertension, capillary resistance is highly elevated and' contractility of vascular smooth muscle is elevated. This is due to increased calcium uptake into the sarcoplasmic reticulum of the vascular smooth muscle. Recently, nifedipine, an antihypertensive medication which inhibits calcium uptake into the vascular smooth muscle is commonly used. It decreases the contractility of the vascular smooth muscle and causes the vessels to relax, which in turn lowers the blood pressure. In 1987, according to Rodriguez-Sargent et al. the increased incidence of cataract in Dahl-salt sensitive rats(DSR) was due to increasd water and sodium contents and decreased potassium content. In this investigative study on hypertension, the water, Sodium and potassium contents in Spontaneous Hypertensive Rats(SHR) were measured. After treatment with nifedipine in SHR, we observed decreased blood pressure along with the changes in water, sodium and potassium contents of the lenses. The following results were obtained from our experiments. 1. In normal SDR, The blood pressure did not decrease with nifedipine injection. 2. After 3-7 days of nifedipine injection bidaily, the blood pressure of SHR did not decrease. 3. After 2 weeks of nifedipine injection bidaily, the blood pressure of the SHR decreased slightly and after 4 weeks of nifedipine injection bidaily, the blood pressure of SHR decreased significantly. 4. Water and sodium contents of SHR were higher than that of SDR and the potassium content was similar to that of SDR. 5. The elevated water and sodium contents of SHR decreased along with decrease of blood pressure, and after 2 weeks of nifedipine injection, showed similar level as the contents of SDR lenses. 6. Potassium contents of SHR lenses showed no change were similar to SDR lines except the 4 weeks nifedipine injection group which showed higher potasslum contents.