Stimulation of renin secretion and calcium efflux from the isolated perfused cat kidney by noradrenaline after prolonged calcium deprivation.

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Abstract
The effects of noradrenaline [NE] [norepinephrine] on the renin secretion and the Ca efflux were investigated in the isolated cat kidney perfused with Locke solution containing the .alpha.-adrenergic blocking agent, phenoxybenzamine, to block increases in renal vascular resistance. NE elicited a marked increase in renin secretion in the absence of any discernible alterations in renal arterial pressure, and prolonged perfusion with Ca-free Locke solution failed to depress NE-evoked renin secretion. NE caused an increase in the efflux of 45Ca from prelabeled kidneys perfused with Ca-free solution. Increasing the NE concentration produced graded increases in 45Ca efflux and renin release, and the peak rise in efflux preceded or coincided with peak renin secretion. DL-Propranolol inhibited the increase in 45Ca efflux and renin release resulting from NE stimulation. Electrical stimulation of the renal nerve enhanced 45Ca efflux and renin release from prelabeled kidneys perfused with normal Locke solution. These findings provide further support for the view that the process of catecholamine-induced renin secretion involves mobilization of Ca from a cellular site.