PROTECTIVE EFFECT OF CICLETANINE ON HYPERTENSION-INDUCED DECREASES IN THE RENAL KALLIKREIN-KININ AND PROSTAGLANDIN SYSTEMS IN STROKE-PRONE SPONTANEOUSLY HYPERTENSIVE RATS

We investigated the effect of two oral (p.o.) doses of cicletanine (5 and 30 mg/kg/day) for 4 weeks on urinary excretion (UKE), renal concentration (RKC) of kallikrein, and prostaglandin E2 (PGE2) and 6-keto-PGF1alpha urinary excretion of stroke-prone (SP) spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) rats submitted to a high sodium intake (1%). Both doses of cicletanine induced a significant antihypertensive effect in treated SHR as compared with hypertensive untreated controls (HC). After 4-week treatment, a significant difference in mortality was observed between normotensive controls (NC) (0%) and HC (84%). Both doses of cicletanine reduced the mortality of hypertensive animals (8% SHR with 5 mg and 24% SHR with 30 mg vs. 84% in HC). Whereas UKE and RKC were decreased in HC during the progression of untreated hypertension from week 1 to week 4, both doses of cicletanine administration significantly prevented this decrease. Consistently with maintenance of UKE during the course of hypertension, the level of tissue kallikrein was higher in hypertensive cicletanine-treated than in untreated SHR. This increased RKC was associated with a significantly higher rate of kallikrein biosynthesis. The increased level of the urinary excretion and tissue concentration of PGE2 and 6-keto-PGF1alpha in cicletanine-treated SHR as compared with untreated animals was also of interest. This protective effect on PG excretion correlated with that on kallikrein excretion. The results confirm the efficiency of cicletatine as an antihypertensive treatment. The antihypertensive action includes protective effects on potential vasodepressor kallikrein-kinin and prostaglandin systems. Furthermore, the effect on the renal kallikrein-kinin system may also indicate a functional improvement in the intracellular homeostasis of the distal connecting tubular cells, the major site for renal kallikrein production. Whereas the cardioprotective effects of angiotensin-converting enzyme (ACE) inhibitors through a kinin-dependent mechanism has already been documented in ischemic hearts, the present data support similar effects in kidney by a new antihypertensive agent not belonging to the ACE inhibitor family.