Like the M 1 and M 3 muscarinic receptor, M 5 receptors are coupled with G proteins of class Gq that upregulate phospholipase C and, therefore, inositol trisphosphate and intracellular calcium as a signaling pathway.
Radioactive iodine is a very effective type of treatment for cancer of the thyroid gland. Thyroid cells absorb iodine. The radioactive iodine from the drink or capsule is absorbed into your body and picked up by the thyroid cancer cells wherever they are. So it can kill the cancer cells even if they have spread.
How and When KI Protects. 1  Potassium iodide (KI) blocks uptake of radioactive iodine by the thyroid gland. 2  KI protects only the thyroid from radioactive iodine uptake. 3  KI is effective as a radiation medical countermeasure only for internal contamination with radioactive iodine.