Final answer:
Atrial Natriuretic Peptide (ANP) increases sodium and water excretion, while suppressing aldosterone and ADH, leading to lower blood pressure and volume without altering osmolarity.
Step-by-step explanation:
The hormone that is an antagonist to Aldosterone and Vasopressin, increasing sodium excretion (and therefore water excretion) without affecting osmolarity is Atrial Natriuretic Peptide (ANP). ANP, produced by the heart's atria, acts as a diuretic by preventing sodium reabsorption by the renal tubules and decreases water reabsorption. It effectively lowers blood pressure and blood volume by promoting the loss of sodium and water from the body while also suppressing the actions of aldosterone, ADH, and renin.