Renin release and autoregulation of blood flow in a new model of non‐filtering non‐transporting kidney.

Abstract

A recently developed model of a non-filtering, non-transporting dog kidney, obtained by an in situ filling of tubules with low-viscosity oil, was applied for studies of renin release and autoregulation of renal blood flow (RBF). RBF was partially autoregulated after oil blockade of tubules, as indicated by a mean autoregulation index of 0.5. This was comparable to autoregulation of the stop-flow kidney (index 0.6) and contrasted with abolition of autoregulation after hypertonic mannitol loading at a stop-flow conditions (index 1.1). The aortic construction at a suprarenal level, which decreased renal perfusion pressure of the oil-blocked kidney 35 .+-. (standard error of mean) 6 mm Hg, produced an increase in arterial plasma renin activity of 1.8 .+-. 0.1 ng ml-1 (P < 0.02). Renin secretion rate decreased 33-70 ng min-1 in 3 dogs in which renal perfusion pressure was reduced to 60-66 mm Hg, but increased 110 .+-. 41 ng min-1 when pressure reductions were kept within the RBF autoregulation range (n = 8, P < 0.025). Signals from the tubular receptor (macula densa) were not necessary for stimulation of renin release or autoregulation of RBF.