Tissue Plasminogen Activator in Essential Hypertension

Nurol Ank, MD, Department of Nephrology, Hacettepe University, Medical School, TR-06100 Ankara (Turkey) Tissue plasminogen activator (t-PA) is regarded as the major activator of fibrinolysis. It is synthetised and stored in endothelial cells, from where it is released into the blood stream. Although several stimuli for t-PA release have been described such as exercise [1], venous occlusion [2] and cardiopulmonary bypass [3], the effect of blood pressure alterations on endothelial t-PA secretion remains to be clarified. It has been attempted to correlate blood fibrinolytic activity with arterial blood pressure in a number of studies [4–8], but no clear-cut conclusions could be attained. Based on these considerations, the present study was designed in order to compare the basal plasma t-PA levels in hypertensive and normotensive subjects and to determine the effect of acute blood pressure reduction by sublingual nifedipine on plasma t-PA levels in essential hypertension. The study group included 18 previously untreated patients with diastolic blood pressure 105 mm Hg or higher, mean age 46 ± 2 years and 13 healthy ageand sex-matched normotensive patients. Blood samples were drawn without stasis, by means of an indwelling catheter placed in the antecubital fossa 30 min prior to test. The patency of the needle was maintained by slow saline infusion. Upon the completion of a 30-min period of recumbent rest, the baseline samples were drawn at 9:00 a.m. in both groups. Immediately after the baseline sampling, the hypertensive patients were given 10 mg nifedipine sub-lingually. Additional samples were drawn 15,30 and 60 min after nifedipine. All subjects remained in the supine position during the study. Blood pressure measurements were performed at 0,15,30 and 60 min just after sampling. T-PA antigen levels were measured by the sandwich ELISA technique [9]. The significance of the difference was analysed by the Mann-Whitney U and Wilcoxon rank tests for intergroup and intragroup measurements, respectively. The values were expressed as mean ± standard error of mean.