Properties of the macula densa mechanism for renin release in the XXXX .

@entity235 @entity3791 @entity1219 @entity1372 @entity7734 @entity3044 @entity432 @entity3352
To study the macula densa mechanism for renin release, both the macula densa and the haemodynamic mechanisms were activated in anaesthetized @entity235 with denervated kidneys, either by renal arterial constriction to a renal arterial pressure (RAP) of 52 +/- 2 mmHg or by @entity432 to a ureteral pressure of 95-105 mmHg, 20-25 mmHg below RAP. Renal arterial constriction increased renin release from 0.3 +/- 0.2 to 16 +/- 4 micrograms AI min-1. At low RAP, renin release was subsequently reduced to 7 +/- 3 micrograms AI min-1 when @entity1372 excretion was raised far above control values by plasma volume expansion and @entity3791 infusion. @entity7734 (3 mg kg-1 body wt.) restored renin release to pre-expansion values, and a large dose (25 mg kg-1 body wt.) prevented renin release from falling even after unclamping the artery. During @entity432 with stopped glomerular filtration, plasma volume expansion, @entity3791 and @entity7734 infusion did not alter renin release. On the other hand, beta-adrenergic stimulation by @entity3044 raised renin release equally (by 30-40 micrograms AI min-1) before and after plasma volume expansion, during both renal arterial constriction and @entity432 . @entity3352 (10 mg kg-1 body wt.) abolished renin release induced by @entity7734 infusion and @entity432 . We conclude that the macula densa mechanism for renin release is inactivated by high @entity1219 reabsorption during plasma volume expansion and @entity3791 infusion, reactivated by inhibition of @entity1219 reabsorption with @entity7734 and completely inhibited by @entity3352 . The degree of activation does not influence the renin release induced by beta-adrenergic stimulation.
