A23-year-old man is brought into the emergency center because of cocaine intoxication. his urine is "tea" colored as a result of breakdown of skeletal muscle by the cocaine, so-called rhabdomyolysis. which of the following describes the fate of myoglobin in the renal tubule?
a. absorbed in the proximal convoluted tubule by active transport by sodium-cotransport
b. absorbed in the proximal convoluted tubule by receptor-mediated endocytosis
c. absorbed in the distal convoluted tubule by facilitated diffusiorn
d. not absorbed or secreted in the urine

b

Explanation:

Myoglobin is a protein red in color, which carries and store oxygen in the muscle cell. Myoglobin is broken down by nephron into small particles and these particles damage the kidney. Proximal Convoluted Tubule is basically destined for this purpose, through receptor-mediated endocytosis myoglobin is absorbed similar to the albumin absorption process.

D. Not absorbed or secreted in the urine

Explanation:

Myoglobinuria occurs when a muscle is damaged for physical or chemical reasons, causing death of its fibers. Then myoglobin is released into the bloodstream and excreted in the urine. The release of myoglobin into the bloodstream mainly harms the kidneys, which cannot remove all the waste from it concentrated in the urine.

This muscle breakdown is called rhabdomyolysis. Although it is a process that can occur for many causes, it is very common in accidents where a muscle is mechanically crushed. Other common causes are heat and excessive physical exertion due to intense exercise, heat stroke, sunburn, broken blood vessels, seizure and strokes. Metabolic problems such as hypothyroidism or diabetic ketoacidosis, among others, can also trigger the problem.