Answer ALL questions please. ALL QUESTIONS 3) Activation of the Histamine Hi rec
ID: 260445 • Letter: A
Question
Answer ALL questions please. ALL QUESTIONS
3) Activation of the Histamine Hi receptor increases vascular permeability, stimulates sensory nerves of airways, and promotes chemotaxis of eosinophils, so can cause sneezing, nasal congestion and rhinorrhea. Activation of the Histamine H2 receptor increases the production of gastric acid in the stomach. Benadryl is an antagonist of the Hi receptor, but not the Hz receptor. Explain how histamine can have two such drastic responses, and why the two receptors do not have the same antagonist. 4) Explain the pathways of the ?18 and ?1A adrenergic receptors seen below Ca2 e Ca2"/calmodulin-dependent VLCC protein kinase II 1B DAG Diacylglycerol (secondary signal) IPs Inositol trip hosphate (secondary signal) T-tubule membrane 0 P-CaMKl PIP2 Phospaidylinositol-4,5- bisphosphate (phospholipid of the cell membrane) PKC Protein Kinase C CaMKI translocation PKCExplanation / Answer
Please find the answers below:
Answer 1: According to the information, whereas H1 receptor of histamine has immunological function, the H2 receptor has digestive function due to its direct involvement in secretion of hydrochloric acid in the stomach. This clearly demonstrates highly diverse functions of the histamine receptors. This diversity of the receptors can be attributed to following features:
Thus, the data clearly suggests that the two histamine receptors follow all the above mentioned reasons for their diversity, hence have extremely different functions. Owing to their structural dissimilarities, they do not have same antagonists for blocking their function.
Answer 2: According to the information, two signalling cascades can be seen in the image. The alpha 1A and 1B mediated intracellular signalling for regulation of PKC expression in the cells. It can be clearly seen that the cytoplasmic domains of these two receptors are G-protein coupled receptors but belong to different classes. These membrane-bound receptor molecules initiate a positive and a negative regulatory system leading to activation and deactivation of PKC expression in the cells, for alpha 1A and 1B receptors, respectively. The activation of the alpha 1A receptor leads to stabilization of PIP2 leading to cytoplasmic accumulation of IP3 and DAG. The battery of events lead to activation of PKC int he cells which undergoes rapid translocation and consequent phosphorylation and activation of CaMKII, thus activating the voltage-gated calcium channels or VLCC. As the VLCC opens, the calcium can come inside and the intracellular concentration of calcium increases, leading to cellular contraction.