The effect of saline loading on blood pressure and catecholamine secretion in the rat and the cat

The effects of acute and chronic saline loading on blood pressure and catechalomine (CA) response in the rat and cat were studied. In the rat, both acute and chronic saline loading stimulated urinary CA excretion without affecting blood pressure; adrenal tyrosine hydroxylase (TH) activity was increased. Pentolinium bitartrate abolished the increase in CA excretion. Chronic saline loading reduced the plasma renin concentration (PRC) and the heart noradrenaline concentration and elevated the plasma cholesterol. Acute infusion of isotonic or hypertonic saline in the cat stimulated adrenomedullary CA secretion. This response was not significantly affected after bilateral cervical vagotomy, but was totally abolished following bilateral nephrectomy. Blood pressure was increased only during the isotonic saline infusion but not during hypertonic saline administration. It is concluded that stimulation of adrenal CA secretion by saline loading is mediated through a renal factor.