Osmoreceptors in the body are activated by changes in blood volume, or body fluid volume and ionic concentration.
ADH, secreted from neurohypophysis, facilitates water reabsorption from latter parts of the tubule, thereby preventing diuresis.
ADH has constrictory effects on blood vessels. This increases the blood pressure.
An increase in blood pressure can increase the glomerular blood flow and thereby the GFR.
ANF can cause vasodilation (dilation of the blood vessels) and thereby decrease the blood pressure.