Enhanced urinary kallikrein excretion in response to a moderate sodium load in genetically hypertensive rats.

Experiments were performed to compare the diuretic and natriuretic response to a moderate saline load between 12-week-old conscious spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) male rats. The animals were infused intravenously with 0.9% NaCl, first for a 1-h equilibration period, at a rate of 20 microliters/min, then for a 2-h salt-loading phase at 40 microliters/min, and finally during a 1-h recovery at 20 microliters/min. Cumulative renal excretion of water and sodium was similar in SHR and WKY rats. In contrast, urinary kallikrein excretion (amidolytic assay) during the saline-expansion and recovery phases was significantly higher in SHR than in WKY rats. At the end of the salt-loading phase, plasma levels of atrial natriuretic peptide (ANP) were higher in SHR than in WKY rats (p less than 0.05). This was also true in animals infused with 5% dextrose instead of 0.9% NaCl. Splanchnic nerve activity remained stable throughout the study in SHR as well as in WKY rats. These data therefore indicate that SHR excrete water and sodium similarly to WKY rats when they are subjected to a moderate sodium load. Neither ANP nor the sympathetic nervous system seems to be directly implicated in the renal response to the moderate saline expansion. Whether the enhanced urinary kallikrein excretion observed in SHR reflects an active participation of the renal kallikrein-kinin system in their sodium handling remains uncertain.

[Methods of estimation of urinary kallikrein activity (author's transl)]. / Méthodes d'estimation de l'activité kallicréine urinaire.

Catalysing the liberation of kinins, vasodilator and sodium duiretic substances, renal and urinary kallikreins are identical. The urinary excretion of kallikrein may be evaluated by various methods, biological, radioisotopic or enzymatic, giving comparable results. Specific radioimmunoassay of urinary kallikrein in man and the rat have been recently published. Details are given of a rapid and convenient enzyme method.

[Renal kallikrein: variations in relation to sodium intake and experimental renovascular hypertension (author's transl)]. / Kallicréine rénale: variations en fonction de l'apport sodé et hypertension rénovasculaire expérimentale.

When rats are submitted to diets with variable sodium, concentration, one may observe a significant increase in the excretion of urinary kallikrein and in the kallikrein activity of the renal tissue in animals in chronic sodium depletion. During experimental renovascular hypertension induced in the rat by stenosis of the renal artery, one may note a significant rise in the excretion of urinary kallikrein; no change in this excretion is observed when the stenosis is associated with nephrectomy on the opposite side. It is possible to consider interrelations between the renin-angiotensin-aldosterone system and the kallikrein-kinin system.