Question

Which of the following flows directly into the bloodstream from its site of production to act on an organ away from it.
A. Glucagon
B. Renin
C. Cholesterol
D. Cholinesterase

Answer 1

Hint: Hormones secreted by the endocrine glands are passed directly into the bloodstream as they are ductless and then they reach their specific target site where they produce their effect. Hormones are very specific in action. Hormones are very essential for living beings as they help in homeostasis.

Complete Step by Step Answer:
Glucagon is a hormone produced by the pancreas. It consists of islets of langerhans which have alpha cells and beta cells. Alpha cells are responsible for the production of glucagon. The hormone acts on hepatocytes (liver cells) and stimulates glycogenolysis which increases the blood sugar level. Here, the site of production and action is not away from each other.

Renin is secreted by the juxtaglomerular (JG) cells in the kidney. When a fall in the renal blood flow is observed, the JG cells activate the prorenin into active renin and directly secretes into the bloodstream. Now renin reaches the liver through the bloodstream and converts angiotensin to angiotensin 1 and then further to angiotensin 2.

Cholesterol are the lipids or a type of fat. They can't be secreted directly into the blood and travel on their own. They need some special proteins called lipoproteins that carry them around the body. Cholesterol is required for the production of various hormones such as sex hormones (estrogen and progesterone), vitamin D and cell membrane etc; but too much of cholesterol can also cause problems.

Cholinesterase is found in the red blood cells and nerve tissue. It is an enzyme that catalyses the breakdown of the neurotransmitter acetylcholine to avoid the over stimulation of postsynaptic nerves, muscles and exocrine glands.

Hence, the correct option is (B)

Note: Low level of renin may cause too much sodium in the body that causes salt-sensitive hypertension. Thus people suffering from low levels of renin must take a low salt diet.