[Preparation of experimental hypertension in mini-pigs]

Attempts at inducing experimental hypertension by loading with NaCl have been undertaken in six Göttingen mini-pigs (G-mini-pigs). In this connection, a paraperitoneal nephrectomy method was established and the renin-angiotensin-aldosterone system after bilateral nephrectomy was investigated. Paraperitoneal nephrectomy was considered to be a safe and convenient method because the operation was accompanied with little hemorrhage and completed in a short time. Using three animals, the renin-angiotensin-aldosterone system was examined after surgical removal of bilateral kidneys. After removal of both kidneys, plasma renin activity decreased rapidly while plasma renin substrate gradually increased. Plasma angiotensin II and aldosterone levels underwent a striking increase. This increase of plasma renin substrate was considered to be due to the presence of an endogenous renin-like substance, while angiotensin II and aldosterone levels appeared to undergo secondary stimulation. Plasma cortisol showed a transient appeared to undergo secondary stimulation. Plasma cortisol showed a transient increase after removal of the two kidneys and they remained at a low level, which implies that the adrenocortical function was normal. In the other three animals, hypertension was induced by NaCl loading and unilateral nephrectomy and the blood pressure remained increased persistently. Concomitantly with this phenomenon, plasma renin activity was gradually suppressed and the aldosterone level showed a similar tendency. It is suggested that sustained hypertension can be induced in G-mini-pigs by NaCl loading combined with unilateral nephrectomy.