<prompt> Answer this question truthfullyWhat is the effect of increased Na delivery, such as increased glomerular filtration rate GFR or renal plasma flow RPF, on the release of ATP adenosine by the macula densa and the constriction of arterioles?  <response>: <reason> In response to increased Na delivery e.g. increased GFRRPF, the macula densa releases ATP adenosine, which constricts the afferent arterioles. 