1. The effect of antidiuretic hormone (ADH) on isoprenaline-stimulated renin secretion was examined in the isolated rat kidney perfused with modified Krebs-Ringer saline.
2. Intrarenal infusion of ADH effectively prevented stimulation of renin secretion by isoprenaline whilst increasing renal perfusion pressure.
3. The exclusion of calcium ions from the perfusion medium abolished the vasoconstrictor effect of ADH and attenuated the inhibitory effect of ADH on isoprenaline-stimulated renin secretion. However, significant suppression of renin secretion was still apparent compared with experiments where isoprenaline was infused alone.
4. These observations indicate that ADH inhibits renin secretion and that this is effected by a direct action on the kidney. Although this may be partly mediated by the rise in renal perfusion pressure, an additional direct effect of ADH on the renin-producing cell, which is dependent on the availability of calcium ions, is proposed.