What is the function of renin in the body?

Renin plays a crucial role in regulating blood pressure within the body. It is an enzyme secreted by the kidneys when they detect low blood pressure or low sodium levels. Upon release, renin acts on a protein called angiotensinogen, transforming it into angiotensin I. This precursor is subsequently converted into angiotensin II, which has several physiological effects, including vasoconstriction—narrowing blood vessels, leading to an increase in blood pressure. Additionally, angiotensin II also stimulates the release of aldosterone, a hormone that promotes sodium and water retention, further contributing to the rise in blood volume and blood pressure.

The other options do not accurately reflect the function of renin. For example, lowering blood sugar levels is primarily the role of insulin, while promoting digestion involves digestive enzymes and hormones such as gastrin. Enhancing respiratory function is not related to renin, but rather to respiratory muscles and how the body responds to oxygen and carbon dioxide levels. Therefore, the association of renin with raising blood pressure distinctly highlights its critical role in cardiovascular homeostasis.