I think when there is an increase in aldosterone secretion in response to an increase in renin by the juxtaglomerular apparatus, then the potassium secretion increases and also sodium reabsorption increases. When a decrease in blood pressure is detected, the adrenal glands are stimulated by the stretch receptors to release aldosterone, which increases sodium reabsorption from the urine, sweat and the gut. This in turn causes increased osmolarity in the extracellular fluid , which in turn returns the blood pressure to normal.
