Acute and chronic diuretic treatment selectively affects vascular permeability in the unanesthetized normal rat

Diuretics are widely used antihypertensive agents, and although their renal actions have been well characterized, the extent of their vascular effects remains to be defined. Because hypertension is associated with numerous vascular complications whose incidences are not always lowered once blood pressure is regulated, this study was undertaken to evaluate the effects of five selected diuretics on capillary permeability to see if they could contribute in some way to these vascular abnormalities. Extravasation of Evans blue dye (EB: 20 mg/kg) injected in the caudal vein of male Wistar rats was used to assess capillary permeability to albumin. Indapamide (0.04 mg/kg), cicletanine (2.0 mg/kg), amiloride (0.3 mg/kg), hydrochlorothiazide (0.5 mg/kg) and furosemide (0.5 mg/kg) were administered by acute i.v. injection or by 10-day "chronic" gavage. EB extravasation was increased in the upper bronchi, lung parenchyma and kidney after acute administration of indapamide (54, 41 and 31%, respectively) and hydrochlorothiazide (45, 41 and 19%, respectively), and increased in all tissues but the duodenum (upper bronchi, lung parenchyma, heart, liver, kidney and muscle; 57-118%) after furosemide. In contrast, capillary permeability was reduced after acute cicletanine in the heart (31%), duodenum (49%) and muscle (58%) and after amiloride in the heart (25%) and muscle (63%). Pretreatment with indomethacin abolished most changes in EB extravasation induced by acute injection of the diuretics. After 10-day gavage, however, changes in capillary permeability were null after amiloride or hydrochlorothiazide treatment, attenuated after cicletanine or furosemide or even reversed after indapamide. Arterial pressure was not affected by diuretic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)