Behavior of the renal kallikrein in spontaneously hypertensive rats: Influence of sexual hormones and aldosterone-sensitive distal nephron ion channels

Abstract

The renal kallikrein-kinin system (RKKS) has been related to blood pressure control and sodium and water balance. We have previously shown that female spontaneously hypertensive rats (SHR) have high urinary kallikrein activity (UKa) and lower blood pressure (BP) than males whereas ovariectomy stimulates UKa and diminishes BP. We also showed that high K+ intake and prepuberal gonadectomy (Gx) diminish BP with a concomitant increase in UKa and plasma aldosterone levels. Since kallikrein co-localize in the same distal nephron segments of aldosterone effectors, we explored the effect of pharmacological blockage of aldosterone receptor, epithelial Na+ (ENaC) and the rectifying outer medulla K+ (ROMK) channels in different gonad contexts on the gene expression, renal tissue content and urine release of kallikrein. Klk1 gene expression was determined by real-time PCR and enzymatic activity of kallikrein by the amidolytic method. We found that the inhibition of the aldosterone receptor by spironolactone increases kallikrein renal tissue storage and decreases its urinary activity, especially in Gx rats. Moreover, ENaC blockade by benzamil increases the renal content of kallikrein without affecting synthesis or excretion, especially in females and Gx animals, while the inhibition of ROMK by glibenclamide increases the synthesis and renal content of kallikrein only in intact male animals. We concluded that RKKS regulation showed sexual dimorphism and seemed to be modulated by sex hormones throughout a process involving aldosterone and the aldosterone-sensitive ion channels.